SYNTHESIS OF PHOTOCLEAVABLE PHOTOSENSITIZER-DRUG

COMPLEXES

by

MICHAEL YANGBO JIANG

B. Sc. Xiamen University, 1998

A THESIS SUBMITTED IN PARTIAL FULFILMENT OF

THE REQUIREMENTS FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

in

THE FACULTY OF GRADUATE STUDIES

(Chemistry)

THE UNIVERSITY OF BRITISH COLUMBIA

May 2007

© Michael Yangbo Jiang, 2007 Abstract

The objective of this work was to develop a "photodyNamic" site-specific drug delivery methodology, whereby a drug can be released by visible light at the site of irradiation.

This goal was fulfilled by connecting the target drug molecule with a photosensitizer through a specially-designed double-bond linkage. Upon visible light illumination, the photosensitizer moiety of the final complex converted ground-state oxygen to the high energized singlet oxygen, which can oxidatively cleave the olefin linkage to release the drug via a tandem [2+2] cyvloaddition-dioxetane decomposition process.

Our first synthetic strategy was to combine bioactive carboxylic acids with alkynylporphyrins using a ruthenium-catalyzed addition reaction. However, the preparation of the alkynylporphyrin substrate was unsuccessful. An alternative synthesis was proposed by adding the carboxylic acid to ethoxyacetylene first, but the subsequent Heck coupling of the resulting alkene to porphyrins failed as well. However, an interesting reaction intermediate

11-21-Zn was isolated and characterized by X-ray crystallography. Its formation mechanism and catalytic activity were also studied.

Second Generation Linker The first generation complexes were successfully synthesized using the linker molecule 111-15.Ester s as drug mimics were first attached to the linker to form an enol ether linkage by Takai alkylidenation and photosensitizers were then attached by esterification.

Visible light illumination of all four complexes gave the desired [2+2] cycloaddition and dioxetane cleavage products in yields from less than 5% to as high as 60%. However, products from the "ene" reaction usually predominated in the photooxygenation.

The second generation linker molecule IV-7 was synthesized to facilitate the assembly of the complexes by Takeda alkoxymethylenation and esterification. Using this strategy, drug molecules (carboxylic acid derivatives) were incorporated through an enediol ether or (8-amino enol ether linkage to give the final complexes as a mixture of Z- and E-stereomers. Despite the unimpressive photooxygenation results of most E-isomers, a complete [2+2] cycloaddition selectivity was observed in the photooxygenation of the Z-isomers, due to the cis-directing effects of the olefin hetero-substituents. Aliphatic and aromatic esters, including methyl esters of ibuprofen and naproxen, lactones, and amides have been successfully incorporated and quantitatively (or near quantitatively) released using this strategy. Table of Contents

Abstract ii

Table of Contents iv

Listoflables x

List of Figures xi

List of Schemes xvi

List of Abbreviations xx

Nomenclature xxiv

Acknowledgements xxv

CHAPTER ONE

Introduction 1

1.1 Porphyrinoids 2

1.2 Chemical Reactions of Singlet Oxygen 5

1.2.1 Overview 5

1.2.2 The [4+2] Cycloaddition 7

1.2.3 The "Ene" Reaction 9

1.2.4 The [2+2] Cycloaddition 11

1.3 Photodynamic Therapy (PDT) 12

1.3.1 Mechanism of Photosensitization 13 1.3.2 Photosensitizers for PDT: Past, Present and Future 15

1.3.2.1 The Historic Aspect and the First Generation PDT Drug 15

1.3.2.2 Criteria of the Ideal PDT Drug 17

1.3.2.3 Second Generation PDT Drugs 18

1.3.2.4 Third Generation PDT Photosensitizers and Current Challenges of PDT. 20

1.4 Research Obj ective 23

CHAPTER TWO

Building Photosensitizer-Drug Complexes Using Palladium-Catalyzed

Cross-Coupling Reactions and Ruthenium-Catalyzed Alkyne Addition Reactions 27

2.1 Design Strategy 28

2.2 Results and Discussion of the Original Design 33

2.3 Modification Using the Heck Cross-Coupling Reaction 37

2.4 Structure Characterization, Formation Mechanism and Catalytic Studies of 11-21-Zn 41

2.4.1 Structure Characterization of 11-21-Zn 41

2.4.2 Mechanism of the Formation of 11-21 -Zn 46

2.4.3 Catalytic Study of 11-21 -Zn 53

2.4.4 hisights into the Reaction Mechanism 54

2.5 Summary 56 CHAPTER THREE

Building Photosensitizer-Drug Complexes with the First Generation Linker Using

Takai Alkylidenation 57

3.1 Olefination of Carboxylic Acid Derivatives Utilizing Titanium Reagents 58

3.1.1 Tebbe, Grubbs, and Petasis Reagents 58

3.1.2 Takai Alkylidenation 61

3.1.3 Takeda Alkylidenation 63

3.2 Design Strategy 67

3.3 Synthesis and Structure Characterizations 71

3.4 Photooxygenation of Photosensitizer-"Drug" Complexes 92

3.4.1 Experimental Design 92

3.4.2 Results and Discussion 94

3.4.2.1 Photooxygenation of TPP-Ethyl Butyrate Complex 111-25 94

3.4.2.2 Photooxygenation of TPP-Ethyl Benzoate Complex 111-26 104

3.4.2.3 Photooxygenation of BPD-Ethyl Benzoate Complex 111-28 107

3.4.2.4 Photooxygenation of TPP-Methyl Pivalate Complex 111-27 112

3.5 Summary 114

CHAPTER FOUR

Building Photosensitizer-Drug Complexes with the Second Generation Linker

Using Takeda Alkoxymethylenation 122 vil

4.1 Design Strategy 123

4.1.1 General Consideration 123

4.1.2 Takeda Alkoxymethylenation Leading to the Enediol Ethers or Other

i8-Hetero-Substituted Enol Ethers 129

4.1.3 Synthetic Approach for Photosensitizer-Drug Complexes Bearing Enediol

Ether or Other /S-Hetero-Substituted Enol Ether Linkages 132

4.1.4 Synthetic Approach for Photosensitizer-Drug Complexes Bearing Enamine

Linkages 134

4.2 Synthesis of Photosensitizer-Drug Complexes Bearing Enamine Linkages 135

4.3 Synthesis of Photosensitizer-Drug Complexes Bearing Enediol Ether or Other

/8-Hetero-Substituted Enol Ether Linkages 137

4.4 Photooxygenation of the Second Generation Photosensitizer-Drug Complexes 143

4.4.1 Photooxygenation of Photosensitizer-Ethyl Butyrate Complexes Bearing

Enediol Ether Linkages 143

4.4.2 Interpretation of Different Behaviors Observed in the photooxygenation of the

First and Second Generation Complexes-—the Cis-Directing Effect 154

4.4.3 Photooxygenation of Other Second Generation Photosensitizer-Drug

Complexes (Z-isomers) 159

4.4.4 Photooxygenation of Other Second Generation Photosensitizer-Drug

Complexes (E-isomers) 166 4.5 Summary 169

4.6 Future Work 171

CHAPTER FIVE

Experimental 181

5.1 Instrumentation and General Materials 182

5.2 Experimental Data for Chapter Two 183

5.3 Experimental Data for Chapter Three 191

5.3.1 Synthesis 191

5.3.2 Photooxygenation 204

5.3.2.1 Photooxygenation of TPP-Ethyl Butyrate Complex 111-25 206

5.3.2.2 Photooxygenation of TPP-Ethyl Benzoate Complex 111-26 209

5.3.2.3 Photooxygenation of BPD-Ethyl Benzoate Complex 111-28 210

5.3.2.4 Photooxygenation of TPP-Methyl Pivalate Complex 111-27 211

5.4 Experimental Data for Chapter Four 212

5.4.1 Synthesis 212

5.4.2 Photooxygenation 240

5.4.2.1 Photooxygenation of TPP-Ethyl Butyrate Complex IV-21-Z 241

5.4.2.2 Photooxygenation of BPD-Ethyl Butyrate Complex IV-22-Z 244

5.4.2.3 Photooxygenation of TPP-Ethyl Butyrate Complex IV-21-E 245 5.4.2.4 Photooxygenation of TPP-Ethyl Benzoate Complex IV-23-Z 247

5.4.2.5 Photooxygenation of TPP-(ô-Valerolactone) Complex IV-24-Z 248

5.4.2.6 Photooxygenation of TPP-(N-Methylbenzanilide) Complex IV-29 249

5.4.2.7 Photooxygenation of TPP-Ibuprofen (methyl ester) Complex IV-25-Z....249

5.4.2.8 Photooxygenation of BPD-Ibuprofen (methyl ester) Complex IV-26-Z...250

5.4.2.9 Photooxygenation of TPP-Naproxen (methyl ester) Complex IV-27-Z....251

5.4.2.10 Photooxygenation of BPD-Naproxen (methyl ester) Complex IV-28-Z.252

5.4.2.11 Photooxygenation of TPP-(ô-Valerolactone) Complex IV-24-E 253

5.4.2.12 Photooxygenation of TPP-Ibuprofen (methyl ester) Complex IV-25-E..254

5.4.2.13 Photooxygenation of BPD-Ibuprofen (methyl ester) Complex IV-26-E.255

5.5 Crystal Data and Details of the Structure Determination 256

References 261 List of Tables

Table 2.1 Selected bond lengths and bond angles for molecule A and B of 11-21-Zn.. 43

Table 2.2 Control experiments to study the in situ reduction of Pd(PPh3)2Cl2 51

Table 3.1 Takai alkylidenation of carbonyl substrates and the desilylation 73

Table 3.2 Esterification of porphyrinoid acids 76

Table 3.3 '^C['H] NMR spectral data of 111-26 (dg-acetone, 100 MHz) 84

Table 3.4 ^H NMR spectral data of 111-28 (de-acetone, 400 MHz) 90

Table 3.5 ^^C[^H] NMR spectral data of 111-28 (de-acetone, 100 MHz) 91

Table 3.6 Photooxygenation of 111-25 95

Table 3.7 Photooxygenation of 111-28 108

Table 4.1 Reactivities of different olefin substrates towards singlet oxygenation 125

Table 4.2 Takeda alkoxymethylenation and the final esterification 139

Table 4.3 Photooxygenation of IV-21 -Z and IV-22-Z 145

Table 4.4 Photooxygenation of IV-21 -E 149

Table 4.5 Photooxygenation of IV-23-Z to IV-29-Z 161

Table 4.6 Photooxygenafion of IV-24-E, IV-25-E, and IV-26-E 167

Table 5.1 Relative GC response factors for esters in Chapter Three 205

Table 5.2 Relative GC response factors for esters and amides in Chapter Four 241

Table 5.3 Crystal data and details of the structure determination for 11-21 -Zn 257

Table 5.4 Crystal data and details of the structure determination for 111-31 259 List of Figures

Figure 1.1 General structures of porphyrinoids 2

Figure 1.2 Structures of protoporphyrin IX, Heme-b, and Chlorophyll-a 4

Figure 1.3 Second generation photosensitizer candidates for PDT 18

Figure 1.4 Photosensitizer-biomolecule conjugates 21

Figure 2.1 Structure of 1-alkoxy enol ester 30

Figure 2.2 Structures of 11-17 and 11-18 36

Figure 2.3 An ORTEP drawing of 11-21 -Zn showing thermal ellipsoids at 50%

probability level (top view). Solvent molecule (CH2CI2) and H atoms have

been omitted for clarity 42

Figure 2.4 An ORTEP drawing of 11 -21 -Zn showing thermal ellipsoids at 5 0%

probability level (side view). Solvent molecule (CH2CI2) and H atoms have

been omitted for clarity 43

Figure 2.5 'H NMR spectrum of 11-21 -Zn (CD2CI2, 400 MHz) 44

Figure 2.6 UV-Vis spectra of ll-2-Zn, il-20-Zn and 11-21 -Zn 46

Figure 3.1 Reactive low-valent titanium species 62

Figure 3.2 Diagram of the proposed linker molecule 67

Figure 3.3 Selective NOE spectra of III-17 (CDCI3, 400 MHz, upon irradiation at 7.43

ppm and 5.32 ppm) 73

Figure 3.4 Photosensitizers used in the synthesis of complexes 74 Figure 3.5 An ORTEP drawing of 111-31 showing thermal ellipsoids at 50% probability

level. H atoms have been omitted for clarity 77

Figure 3.6 Selective NOE spectra of 111-25 (de-acetone, 400 MHz, upon irradiation at

4.62 ppm and 2.09 ppm) 78

Figure 3.7 Selective NOE spectra of 111-27 (CeDe, 400 MHz, upon irradiation at 4.77

ppm and 1.16 ppm) 79

Figure 3.8 'H, and APT spectra of 111-26 (de-acetone, 400 MHz/100 MHz) 81

Figure 3.9 HMQC spectrum of 111-26 (de-acetone, 400 MHz) 82

Figure 3.10 HMBC spectrum of 111-26 (de-acetone, 400 MHz) 83

Figure 3.11 'H, '^C['H], and APT spectra of 111-28 (de-acetone, 400 MHz/100 MHz)... 86

Figure 3.12 COSY spectrum of 111-28 (de-acetone, 400 MHz) 87

Figure 3.13 HMQC spectrum of 111-28 (de-acetone, 400 MHz) 88

Figure 3.14 HMBC spectrum of 111-28 (de-acetone, 400 MHz) 89

Figure 3.15 UV-Vis spectra of 111-25 to 111-28 in CH2CI2 92

Figure 3.16 'H NMR spectral sequence of the photooxygenation of 111-25 (CDCI3, 400

MHz) 98

Figure 3.17 COSY spectrum of the photooxygenation crude mixture of 111-25 (CDCI3,

400 MHz, 50 min irradiation) 99

Figure 3.18 '^C['H] NMR and APT spectra of the photooxygenation crude mixture of

111-25 (CDCI3, 100 MHz, 50 min irradiation) 101 XIU

Figure 3.19 HMQC spectrum of the photooxygenation crude mixture of 111-25 (CDCI3,

400 MHz, 50 min irradiation) 102

Figure 3.20 HMBC spectrum of the photooxygenation crude mixture of 111-25 (CDCI3,

400 MHz, 50 min irradiation) 103

Figure 3.21 ^H NMR spectral sequence of the photooxygenation of 111-25 (de-acetone,

400 MHz) 116

Figure 3.22 COSY spectrum of the photooxygenation crude mixture of 111-25

(de-acetone, 400 MHz, 30 min irradiation) 117

Figure 3.23 'H NMR spectral sequence of the photooxygenation of 111-25 (CD2CI2, 400

MHz, -78 °C) 118

Figure 3.24 COSY spectrum of the photooxygenation crude mixture of 111-25 (CD2CI2,

400 MHz, -78 °C, 4 h irradiation) 119

Figure 3.25 COSY spectrum of the photooxygenation crude mixture of 111-26 (CeDe, 400

MHz, 22 min irradiation) 106

Figure 3.26 'H NMR spectral sequence of the photoirradiation of 111-28 (CeDe, 400

MHz) 110

Figure 3.27 COSY spectrum of the photooxygenation crude mixture of 111-28 (CeDg, 400

MHz, 50 min irradiation) Ill

Figure 3.28 ^H NMR spectral sequence of the photooxygenation of 111-28 (de-acetone,

400 MHz) 120 Figure 3.29 COSY spectrum of the photooxygenation crude mixtiire of 111-28 (de-acetone,

400 MHz, 80 min irradiation) 121

Figure 3.30 COSY spectrum of the photooxygenation crude mixture of 111-27 (CeDe, 400

MHz, 25 min irradiation) 114

Figure 4.1 'h NMR spectral sequence of the photooxygenation of IV-21 -Z (CeDe, 400

MHz) 146

Figure 4.2 COSY spectrum of the photooxygenation crude mixture of IV-21 -Z (CeDe,

400 MHz, 4 min irradiation) 147

Figure 4.3 'H NMR spectral sequence of the photooxygenation of IV-21 -Z (CDCI3,400

MHz) 172

Figure 4.4 COSY spectrum of the photooxygenation crude mixture of IV-21 -Z (CDCI3,

400 MHz, 2 min irradiation) 173

Figure 4.5 ^H NMR spectral sequence of the photooxygenation of IV-21 -Z

(CDClsiMeOD = 4:1, 400 MHz) 174

Figure 4.6 'H NMR spectral sequence of the photooxygenation of IV-21 -Z (de-acetone,

400 MHz) 175

Figure 4.7 'H NMR spectral sequence of the photooxygenation of IV-21 -Z (de-acetone

with DABCO, 400 MHz) 176

Figure 4.8 'H NMR spectral sequence of the photooxygenation of IV-22-Z

(CeDe :de-acetone = 5:1, 400 MHz) 148 Figure 4.9 'H NMR spectral sequence of the photooxygenation of IV-21 -E (CeDe, 400

MHz) 150

Figure 4.10 Field-effect analysis of IV-34-E 151

Figure 4.11 'H NMR spectral sequence of the photooxygenation of IV-21 -E in various

solvents (400 MHz) 152

Figure 4.12 COSY spectrum of the partially purified hydroperoxide mixture (de-acetone,

400 MHz, entry 1, Table 4.4) 153

Figure 4.13 ^H NMR spectral sequence of the photooxygenation of IV-23-Z (CeDe, 400

MHz) 177

Figure 4.14 ^H NMR spectral sequence of the photooxygenation of IV-24-Z (de-acetone,

400 MHz) 178

Figure 4.15 'H NMR spectral sequence of the photooxygenation of IV-27-Z (CeDe, 400

MHz) 179

Figure 4.16 'H NMR spectral sequence of the photooxygenation of IV-28-Z ((CeDe, 400

MHz) 180 List of Schemes

Scheme 1.1 Ground and excited states of dioxygen 5

Scheme 1.2 Reactions of singlet oxygen 6

Scheme 1.3 Examples of singlet oxygenation of heterocyclic compounds 7

Scheme 1.4 [4+2] Cycloaddition of dienes with singlet oxygen 8

Scheme 1.5 Proposed mechanisms for the singlet oxygen "ene" reaction 10

Scheme 1.6 Proposed mechanisms for the [2+2] singlet oxygen cycloaddition reaction 12

Scheme 1.7 Modified Jablonski diagram of photosensitization 14

Scheme 1.8 Synthesis of Photofrin® (only one dimeric form of the HpDs is shown) 16

Scheme 1.9 Synthesis of BPDMA 19

Scheme 1.10 Potential photochemotherapeutic agents and DNA cross-linking

mechanism 22

Scheme 1.11 [2+2] Singlet oxygen cycloaddition reaction in Woodward's total synthesis

of chlorophyll 24

Scheme 1.12 Photocleavable cyclodextrin carrier for PDT photosensitizers 25

Scheme 2.1 lodination and Sonogashira alkynylation of 11-1 28

Scheme 2.2 Ruthenium-catalyzed addition of carboxyhc acids to alkynes 29

Scheme 2.3 Singlet oxygenation of enol lactone 11-4 30

Scheme 2.4 Singlet oxygenation of enol ester 11-5 30

Scheme 2.5 Proposed synthetic roadmap of incorporation and release of bioactive acids 32

Scheme 2.6 Retrosynthetic routes to 11-1 33

Scheme 2.7 Acid-catalyzed scrambling of 11-12 34

Scheme 2.8 Synthesis of 11-19 38

Scheme 2.9 General mechanism of the Heck cross-coupling reaction 39

Scheme 2.10 Heck coupling using Pd(PPh3)2Cl2 as catalyst 40

Scheme 2.11 Mechanism of the i« 5ZYM reduction of Pd(0Ac)2 48

Scheme 2.12 The reduction of Pd(PhCN)2Cl2 by EtaN 49

Scheme 2.13 Synthesis of ll-22-Zn 53

Scheme 2.14 Catalytic Study of 11-21-Zn 54

Scheme 2.15 Insights into mechanisms of cross-coupling reactions using

Pd(PPh3)2Cl2/Et3N system 55

Scheme 3.1 Carbonyl methylenation using the Tebbe reagent 59

Scheme 3.2 Synthesis of the Grubbs reagent 59

Scheme 3.3 Synthesis of the Petasis reagent 60

Scheme 3.4 Takai alkylidenation of carboxylic acid derivatives 61

Scheme 3.5 Reaction intermediates in Takai alkyhdenation 62

Scheme 3.6 Takeda alkylidenation using the thioacetal-Cp2Ti[P(OEt)3]2 system 63

Scheme 3.7 Reactions of III-5 and olefins 65

Scheme 3.8 Takeda alkyhdenafion using ge/n-dichloride-Cp2Ti[P(OEt)3]2 system 66 Scheme 3.9 Takeda alkylidenation using alkyl halide-Cp2Ti[P(OEt)3]2 system 67

Scheme 3.10 General diagram of the sensitizer-drug complex synthesis and the drug

release 69

Scheme 3.11 Proposed synthesis of the linker molecule and sensitizer-drug complexes... 70

Scheme 3.12 Synthesis of 111-22 75

Scheme 3.13 Mechanism of Steglich esterification 77

Scheme 3.14 Rearrangement of III-29-TPP 77

Scheme 3.15 NMR spectral sequence of the photooxygenation of 111-26 (CÔDÔ, 400

MHz) 105

Scheme 3.16 ^H NMR spectral sequence of the photooxygenation of 111-27 (C^D^, 400

MHz and 300 MHz) 113

Scheme 4.1 Singlet photooxygenation of enediol ethers 124

Scheme 4.2 Singlet photooxygenation of enamines 126

Scheme 4.3 Mechanism of the a-amino dioxetane cleavage 127

Scheme 4.4 Singlet photooxygenation of vinyl sulfides 128

Scheme 4.5 Takeda olefination using dithio- or trithioorthoformates 130

Scheme 4.6 Takeda alkoxymethylenation using alkoxymethyl chloride 131

Scheme 4.7 Synthesis of dithioorthoformates for Takeda alkoxymethylenation 132

Scheme 4.8 Proposed synthesis of the linker IV-7 and final photosensitizer-drug

complexes 133 Scheme 4.9 Proposed synthesis of photosensitizer-drug complexes bearing enamine

linkages 134

Scheme 4.10 Synthesis of photosensitizer-drug complexes bearing enamine linkages 135

Scheme 4.11 Suggested mechanism of the amidation using the coupler IV-11 136

Scheme 4.12 Stereochemistry assignments for IV-17-Z/E by the field-effect analysis of

NMR spectrum of the mixture (CeDe, 400 MHz) 141

Scheme 4.13 Examples of the cis-directing effect 155

Scheme 4.14 HOMO-LUMO interactions for the cis-directing effect 157

Scheme 4.15 Interpretation of the photooxygenafion results by the cis-directing effect.... 158

Scheme 4.16 'H NMR spectral sequence of the photooxygenation of IV-29-Z/E (CeDe,

400 MHz) 163

Scheme 4.17 'H NMR spectral sequence of the photooxygenafion of IV-25-Z (CeDe, 400

MHz) 164

Scheme 4.18 'H NMR spectral sequence of the photooxygenation of IV-26-Z (CeDe, 400

MHz) 165

Scheme 4.19 'H NMR spectral sequence of the photooxygenation of IV-24-E and IV-26-E

(CôDô, 400 MHz) 168

Scheme 4.20 'H NMR spectral sequence of the photooxygenation of IV-25-E (CeDe, 400

MHz) 169 List of Abbreviations

AIDS Acquired Immunodeficiency Syndrome

ALA aminolevulinic acid

AMD age-related macular degeneration anal. analytical

APT attached proton test aq. aqueous

BINAP 2,2'-bis(diphenylphosphino)-l,l'-binaphthyl

BPD benzoporphyrin derivative

BPDMA benzoporphyrin derivative monoacid ring A br. broad (NMR) calcd. calculated

CI chemical ionization cone. concentrated d doublet

DABCO 1,4-diazabicyclo[2.2.2]octane dba dibenzylidene acetone

DCC dicyclohexylcarbodiimide

DCM dichloromethane (or methylene chloride)

DDQ 2,3-dichloro-5,6-dicyano-l,4-benzoquinone

Die N,N'-diisopropylcarbodiimide

DMAD dimethylacetylene dicarboxylate

DMAP 4-dimethylaminopyridine

DMF N,N'-dimethylformamide

DPP 5, 15-diphenylporphyrin dppe 1,2-bis-(diphenylphosphino)ethane

EDC l-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride eq. equivalent(s)

ESIMS electrospray ionization mass spectrometry

FDA food and drug administration

FID flame ionization detector

GC gas chromatography

GP general procedure

h hour(s)

HMBC heteronuclear multiple bond correlation

HMQC heteronuclear multiple quantum coherence

HOMO highest occupied molecular orbital

Hp hematoporphyrin

HpD hematoporphyrin derivatives

HPLC high performance liquid chromatography

HRESIMS high resolution electrospray ionization mass spectrometry

IS internal standard

ISC intersystem crossing

LRESIMS low resolution electrospray ionization mass spectrometry

LSIMS liquid secondary ionization mass spectrometry

LUMO lowest unoccupied molecular orbital lUB International Union of Biochemistry lUPAC International Union of Pure and Applied Chemistry m meta m multiplet

MCCA mixed carboxylic-carbonic anhydrides m/e mass to charge ratio min minute(s)

MS mass spectrometry Mois molecular sieves

n/a not available

NMR nuclear magnetic resonance

NOE nuclear overhauser effect

ORTEP oak ridge thermal ellipsoid plot

PDT photodynamic therapy

Por porphyrinoid

PpDC protoporphyrin IX ppm parts per milhon prep. preparative (TLC) r. t. room temperature

R/ retention factor

s singlet

SAR structure-activity relationship sat. saturated sec seconds(s) s.m. starting material t triplet

TBAF tetrabutyl ammonium fluoride

TBDMS tert-butyldimethylsilyl

TES triethylsilyl

TFA trifluoroacetic acid

THF tetrahydrofuran

THP tetrahydropyran

TIPS triisopropylsilyl

TLC thin layer chromatography

TMEDA N,N,N',N'-tetramethylethylenediamine TMS trimethylsilyl

TPE two-photon excitation

TP? 5, 10, 15, 20-tetraphenylporphyrin

Tr retention time

TsOH /(-toluenesulfonic acid

UV-Vis ultraviolet-visible Nomenclature

Porphyrins and Chlorins

The lUPAC-IUB numbering system of tetrapyrroUc macrocycles are used in this work.

The numbering scheme of the peripheral carbon atoms and the inner nitrogen atoms of a porphyrin is shown below. Conventionally, positions 1,4,6, 9,11,14,16 and 19 are referred to as "of' positions, with 2, 3, 7, 8, 12, 13, 17 and 18 as positions and 5, 10, 15 and 20 as

"we^'o" positions.

Ring B-BPD-7^-monoacid and its esterification derivatives are the chlorins studied in this thesis and its numbering scheme is shown below. Acknowledgements

First of all, my foremost gratitude goes to my supervisor. Professor David Dolphin, for his guidance, wisdom, patience and support during the entire course of my research.

Members of Dolphin's group, past and present, are sincerely appreciated. Without them, my past several years would not have been so enjoyable and fruitful. Especially, I would like to thank Dr. Yongjun Zhang and Dr. Alison Thompson for their help and encouragement during the early stage of this research project. Special thanks go to Dr. Ji-Young Shin, who has provided me with invaluable advice and unreserved help and support. I am also grateful to Mr.

Andrew Tovey, Dr. Yan Li and Dr. Olivia New for their kind proofreading and precious critiques for this thesis.

I have to thank the staff in the labs of NMR, Mass Spectrometry and X-Ray, as well as in the administrative office, for their hard work and great services.

Last, but not least, I would like to express my deep sense of gratefulness to my family: to my parents, Mr. Zhenfa Jiang and Mrs. Xiuhua Wu for their love, support and encouragement over the years; to my newborn baby Vivian, who has given me so much strength during the preparation of this thesis; and to my dear wife Sarah, without her sweet smile, constant inspiration, and wholehearted help, I could not have gone this far. CHAPTER ONE

Introduction 3.1 Porphyrinoids

Porphyrinoids are aromatic macrocycles, including porphyrins, chlorins,

bacteriochlorins, isobacteriochlorins, etc.. The common structural backbone of porphyrinoids

consists of four pyrrol-type five-membered rings bridged by methine groups (Figure 1.1).'

bacteriochlorin isobacterioch lorin

Figure 1.1 General structures of porphyrinoids

Li addition to the structural similarity, porphyrins and related tetrapyrroUc macrocycles are interconvertible through reduction reactions. As for porphyrins, 18 out of their 22 total 7r-electrons participate in a cyclic delocalization pathway (as illustrated by bold circuits in Figure 1.1), which complies with Hiickel's 4n+2 rule for aromaticity (n=4). As a result, two cross-conjugated double bonds, which are not the part of the cyclic conjugation pathway, are relatively reactive and can be reduced without affecting the aromaticity. Chlorins are generated through the reduction of one such bond and the further reduction of the other gives either bacteriochlorins or isobacteriochlorins, depending on the relative positions of these reduced bonds. The aromaticity of porphyrinoids is manifested by planar skeletons and a strong ring current effect. The latter is demonstrated by their 'H NMR spectra wherein tremendous upfield and downfield shifts are observed for the signals of inner NH protons and peripheral protons respectively, due to the shielding and deshielding effects.'^

One remarkable structural feature of porphyrinoids is the placement of four inner nitrogen atoms for metal chelation, which can occur after deprotonation of the inner amino nitrogen atoms. Almost all the metals and some semimetals in the periodic table have been reported to complex with porphyrinoids.^ In addition, the inner imino nitrogen atoms are basic as they can be protonated by strong acid to give dications.

Porphyrinoids exhibit characteristic optical absorption properties in the UV-visible region.'^' Porphyrins have an intense absorption band at around 400 nm (Soret or B band, e =

1 ~ 4x10^ M' cm" ), and four absorption bands of lower intensity in the visible region from

450 to 650 nm (Q-bands). After metal insertion or transformation of porphyrins into dications or dianions, the molecular symmetry is increased from D2h to D4h, which results in the contraction of Q-bands from four to two. Compared to porphyrins, chlorins have a less intense

Soret band while their Q-band with the longest absorption wavelength is intensified by ca. 10 times and bathochromically shifted by about 25 nm. Moreover, due to the asymmetric nature of chlorins, no simplification of optical spectra can be observed after the metal insertion.

Some metallated porphyrinoids play crucially important roles in various living systems. For this reason, they are commonly referred to as the "pigments of life".^ Heme (also called Heme-6)^ and chlorophyll-a serve as good examples (Figure 1.2).'' Heme is the iron(II) complex of protoporphyrin IX (PpIX), functioning as the prosthetic group of hemoproteins

such as hemoglobin and myoglobin, which are responsible for oxygen transportation and

storage in human body. While chlorophyll-a, the most abundant chlorophyll, is a

magnesium(II) chlorin, which is vital for photosynthesis in green plants. Photosynthesis is the

most important biochemical process in nature whereby the photonic energy is transformed

into chemical energy, generating oxygen and carbohydrates. Without it, most lives on this

planet can not survive.

M = H2, Protoporphyrin IX Chlorophvll-a M = Fe(ll), Heme-b

Figure 1.2 Structures of protoporphyrin IX, Heme-ô, and Chlorophyll-a

In addition to their important roles in living systems, porphyrinoids have also found broad industrial and medical applications.* Due to their ability to convert tissue oxygen into cytotoxic singlet oxygen, some porphyrinoids have been successfully developed as photosensitizers in photodynamic therapy (PDT),^ which will be elaborated upon in section

1.3. 1.2 Chemical Reactions of Singlet Oxygen

1.2.1 Overview

The ground state of dioxygen is a triplet state due to two parallel spins of HOMO

electrons. There are two singlet excited states of dioxygen, 'Ag and ^Eg^, lying 22.4 kcal mol"'

and 37 kcal mol"' above the ground state respectively (Scheme 1.1). Since the relaxation from

'Eg^ to 'Ag is spin-allowed while that from 'Ag to ^Eg" is spin-forbidden, only the first singlet

state 'Ag is stable enough (lifetime ranges from 1 ms to 1 /is) to participate in reactions in

solution and therefore it is commonly referred to as "singlet oxygen"."'

HOMOs Of < the excited states 37 kcal/ mol 22.4 kcal/ HOMO of mol the ground state

Scheme 1.1 Ground and excited states of dioxygen

Unlike the ground state triplet oxygen which shows a diradical character, the diamagnetic singlet oxygen undergoes two-electron reactions. A large variety of olefins, dienes, heterocyclic compounds, sulfides and phosphines have been reported to react with singlet oxygen (Scheme 1.2).'^ The reactions between singlet oxygen and olefin substrates consist of three modes: the [4+2] cycloaddition with a diene to give an endoperoxide, the "ene" reaction leading to a hydroperoxide, and the [2+2] cycloaddition to an activated double bond to form a 1,2-dioxetane. Heterocyclic compounds react with singlet oxygen in a similar way to olefin substrates (the aforementioned three modes), except that the initial products are usually too unstable to be isolated and often undergo complex secondary reactions such as rearrangements and decompositions (Scheme 1.3).'^' Importantly, these various reactions form the chemical basis of the cytotoxicity of singlet oxygen.

[4+2] /= ^ Cycbaddition >^

Endoperoxide

OOH / Reactions witii "ene" Olefins < Reaction Hydroperoxide

0-0 [2+2] Cycloaddition Dioxetane

n O ln M In II Reactions with ^Sv > ^Sv Reactions with Sulfides R R' R R' Phosphines ^ R- ^ ^ R'

Scheme 1.2 Reactions of singlet oxygen Scheme 1.3 Examples of singlet oxygenation of heterocyclic compounds

Since the reactions of singlet oxygen with olefins are of pivotal importance to the design strategy of this project, details of the three reaction modes will be discussed in the following sections.

1.2.2 The [4+2] Cycloaddition

Analogous to the Diels-Alder reaction, the [4+2] cycloaddition of singlet oxygen to

1,3-dienes requires substrates to attain the s-cis conformation.'^ It is generally accepted that the reaction is concerted, as supported by the experimental observations of suprafacial stereochemistry and neghgible solvent effects of the reaction.'^'

The 1,3-dienes substrates can be classified into five categories:'^ 1) nonhomoannular aliphatic dienes, 2) homoannular aliphatic dienes, 3) alkenylarenes, 4) heterocyclic aromatic dienes and 5) nonheterocyclic aromatic dienes, as shown in Scheme 1.4.'^' '^ It is noteworthy that for the reactions involving aromatic substrates (category 3 through category 5), the aromaticity is either impaired or completely destroyed. As for alkenylarenes, one of the aromatic double bonds participates as part of the diene to react with singlet oxygen and the resulting bicyclic diene can undergo another [4+2] cycbaddition of singlet oxygen to furnish a tricyclic product.

1) Nonhomoannular aliphatic diene

2) Homoannular aliphatic diene

3) Alkenylarene

4) Heterocyclic aromatic diene

5) Nonheterocyclic aromatic diene

Scheme 1.4 [4+2] Cycloaddition of dienes with singlet oxygen Endoperoxide products from the [4+2] singlet oxygenations of dienes can undergo

thermal rearrangements to dioxetanes or solvolysis to give hydroperoxides.'*

1.2.3 The "Ene" Reaction

Among the three typical reaction modes of singlet oxygenation of olefins, the "ene" reaction has been studied most exhaustively, due to its great synthetic value of generating allylic hydroperoxides (or potentially hydroxides after reduction) from olefins and its intriguing regiochemistry and stereochemistry.'^

Experimental results have revealed some interesting aspects regarding this reaction.''''

'^' First of all, the reaction is suprafacial as the oxygen addition and the hydrogen abstraction occur from the same face of the double bond. Secondly, only the allylic hydrogen with proper alignment, i.e., perpendicular to the olefin plane, is abstracted. Thirdly, the

Markovnikov rule is not applicable in determining the product distribution. And finally, it is often found that the hydrogen abstraction occurs predominately to the more congested side of the alkene, a phenomenon known as the cis-directing effect.^*'

Different mechanisms and intermediates have been proposed for this reaction, including a concerted process,^' a biradical intermediate,^^ a zwitterion intermediate,^^ a perepoxide intermediate,'^'' and the reversible formation of an exciplex without an intermediate^^ (Scheme 1.5). More recently, it has been suggested that the reaction might proceed via two transition states without an intervening intermediate.^^ However, the mechanism involving the perepoxide intermediate has been extensively accepted as it nicely accounts for the aforementioned experimental results and its validity has been further confirmed by kinetic isotope effect studies'27-2 9 and reaction intermediate trapping experiments. " In fact, the interesting regio- and stereoselectivity of "ene" reactions can be explained by the activation-energy difference of the competing H-abstraction pathways to reach perepoxide-like transition states (details will be discussed in section 4.4.2). Indeed, by assuming the perepoxide intermediate, the regio- and stereoselectivity of the "ene" reaction has been rationally designed and achieved by manipulating hydrogen-bonding, electronic or steric interactions between alkene substituents and the tail oxygen of the developing perepoxide intermediate.^^"^^

H

Reaction Hydroperoxide

concerted biradical zwitterion perepoxide excipiex

Scheme 1.5 Proposed mechanisms for the singlet oxygen "ene" reaction

The hydroperoxide products fi^om the "ene" reaction can undergo Hock-type rearrangement to carbonyl fi-agments (usually catalyzed by acid) or 1,3-allylic isomerization.'^ 1.2.4 The [2+2] Cycloaddition

The [2+2] cycloaddition of singlet oxygen to olefins is observed on those activated

by electron rich substituents, such as enol ethers, enamines and vinyl sulfides, and on olefins

without geometrically accessible allylic hydrogens.^^ Despite the fact that the [2+2]

cycloaddition mode generally competes ineffectively with the "ene" and the [4+2]

cycloaddition modes, its chemoselectivity can be greatly enhanced by increasing the electron

richness of alkenes substrates, elevating the solvent polarity or lowering the reaction

temperature.^^""*^

Unlike the "ene" reaction where a perepoxide-involved mechanism is generally

agreed upon, the mechanism of the [2+2] cycloaddition remains somewhat controversial. This

is partially due to the limited number of approaches available for the mechanism study. A kinetic isotope effect study (deuterium involved) is not applicable here and the singular product (dioxetane) makes it impossible to acquire information from the product distribution pattern or from the Markovnikov effect analysis. Like the "ene" reaction, various mechanisms and intermediates have been suggested for the [2+2] cycloaddition (Scheme 1.6), including a

Woodward-Hoffman-allowed [2s+2a] concerted process,'*'^' '^'^ a biradical intermediate,^^ a zwitterion intermediate,^^ a perepoxide intermediate,'''' '^^ and an intermediate exciplex^^.

The biradical intermediate can be easily ruled out as the dioxetane formation is not hampered by the addition of radical quenchers.'*^ In addition, major results indicate the reaction is stereospecific, which obviously favors the concerted process as well as the perepoxide intermediate. On the other hand, the increased chemoselectivity of the [2+2] cycloaddition in polar solvents and with high electron-donating substituents tends to support the argument of polar intermediates such as the zwitterion and the perepoxide intermediates over the concerted

process. Overall, the perepoxide-involved (interchangeable with the zwitterion intermediate)

mechanism seems to be the most favored''^' and is strongly supported by the sulfoxide

trapping experiment of Schaap et alJ^

[2+2] Cycloaddition Dioxetane

+ Q 'O2 or or or

O [2s+2a] biradical perepoxide zwitterion excipiex conœrted

Scheme 1.6 Proposed mechanisms for the [2+2] singlet oxygen cycloaddition reaction

Dioxetanes are generally unstable and can readily decompose to two carbonyl

fragments, with concomitant luminescence. This fascinating feature has been exploited in the

medical field as some carefully designed dioxetanes can generate enzyme-triggered

chemiluminescence to diagnose AIDS, cancer, hepatitis and other diseases.''^"^'

1.3 Photodynamic Therapy^'

Photodynamic therapy, by definition,^ is "a medical treatment which employs the combination of light and a drug to bring about a cytotoxic or modifying effect to cancerous or otherwise unwanted tissue". However, it needs to be emphasized that the involvement of oxygen is equally important in this treatment. A typical PDT process^^ starts with the intravenous injection of a certain amount of a photosensitizer. After entering the bloodstream, the photosensitizer complexes with low-density lipoproteins (LDL). Since cancerous tissue or abnormal blood vessels undergo rapid cell division and require a higher-than-normal supply of LDL, the photosensitizer can selectively accumulates in these tissues. After a certain period

(the so-called "drug-to-light interval"),^^ visible light of a particular wavelength is shone selectively onto the diseased areas, triggering the photosensitizer to convert the tissue oxygen into the cytotoxic singlet oxygen, which in turn destroys the diseased cells. The dual selectivity of selective accumulation and selective illumination, makes PDT an advantageous treatment modality compared to conventional radiotherapy and chemotherapy with regard to patient safety and healthy tissue damage.

1.3.1 Mechanism of Photosensitization

The general mechanism^' of photosensitization is depicted in the modified

Jablonski diagram (Scheme 1.7). Upon light irradiation, the photosensitizer is excited from the ground state So to an excited state Sn, which can undergo collisional deactivation to the first singlet excited state S\. S\ is a short-lived excited state (ca. 10"* s lifetime), and can readily relax to So either radiatively via fluorescence or thermally via internal conversion or to the first triplet Ti via a spin-forbidden intersystem crossing (ISC). The high efficiency towards the ISC is an important prerequisite for a photosensitizer to be used in PDT. Ti can relax back to So either radiatively by phosphorescence or non-radiatively by spin exchange with another triplet state molecule such as oxygen. Since both processes are spin-forbidden, the lifetime of

Ti is much longer (ca. 10'^ s) compared to that of Si. The spin exchange between Ti and the triplet ground state oxygen leads to the generation of the excited singlet oxygen. Such energy transfer process is commonly termed as a "Type II" process. As discussed in section 1.2, singlet oxygen can react with a broad range of biomolecules and result in damage to membranes, proteins, enzymes and nucleic acids. On the other hand, the excited states Si^^ or

T] of the photosensitizer can react with an easily reduced or oxidized substrate via an electron or hydrogen transferring "Type I" process, giving rise to peroxide or superoxide species in the presence of oxygen.^^' ^'^ However, evidences suggest that the singlet oxygen-involved Type II process should take the major responsibihty for cell destruction in PDT.^

1. Absorption of Light 2. Fluorescence 3. Internal Conversion 4. Intersystem Crossing S, z n 5. Phosphorescence 6. Singlet Oxygen Production (energy transfer) 7. Hydrogen or Electron Transer

o c UJ

Scheme 1.7 Modified Jablonski diagram of photosensitization 1.3.2 Photosensitizers for PDT: Past, Present and Future

1.3.2.1 The Historic Aspect and the First Generation PDT Drug'' "

Despite the fact that ancient Egyptians used the plant containing psoralen and sunlight to treat vitiligo as early as 4000 years ago, the medicinal application of photosensitizers was not discovered until 1900 when Raab found the combination of acridine dyes and light effectively kills the unicellular organism Paramecium.In 1913, Meyer-Betz first demonstrated the photodynamic effect of porphyrin-based photosensitizers on human beings by conducting a heroic experiment:^^ he injected himself 200 mg of hematoporphyrin

(Hp) and suffered severe swelling on his face and hands after exposure to sunlight; and he remained photosensitive for several months. The phototoxic effect of porphyrins was verified by Policard in 1925,*^^ and the accumulation of Hp in cancerous tissue was found by Auler and

Banzerin 1942.^''

A revisit of Meyer-Betz's experiment by Schwartz in the early 1950s indicated that it was the oligomeric mixture rather than the monomer of Hp that was responsible for the long- term cytotoxic effect.^^ Simultaneously, it was found that the oligomeric fraction can be enriched by treating Hp with acid then alkali, and the resulting product was named hematoporphyrin derivative (HpD) (Scheme 1.8). In 1964, Lipson, then a Master student in

Schwartz's group, observed the preferential accumulation of HpD in cancerous tissue in mice.^*' This led to the clinical trials of HpD for cancer treatment by Dougherty in the 1970s.^^'

Attempts to identify and subsequently isolate the most active component were unsuccessful as HpDs with various chain lengths showed comparably modest PDT effects.^^ However, progress was made towards the purification of HpD mixture by Dougherty and co-workers using ultrafiltration (the resulting material was designated as Photofiin 11®)/°' ^' and later by

QLT inc. and American Cyanamid using lyophilization to give the drug Photofiin®.^^

Photofiin® is the first PDT photosensitizer to be granted regulatory approval (Canada, 1993) for the treatments of certain cancers.

As the first generation PDT drug, Photofiin® suffers from a number of drawbacks.^

First, the complex composition of the drug makes it very difficult to reproduce as well as to establish the structure-activity relationship (SAR). Secondly, its pharmacokinetic profile is not satisfactory, resulting in the prolonged general (skin) sensitivity after treatment. Thirdly, the longest wavelength absorption of Photofiin® is a weak Q-band at ca. 630 nm and the tissue transmittance at this wavelength is only limited due to endogenous chromophore absorption

{e.g. hemoglobin) and light scattering. 1.3.2.2 Criteria of the Ideal PDT Drug

The unsatisfactory aspects of Photofrin® as a PDT photosensitizer prompted scientists to seek its substitutes with improved therapeutic effects and biological properties.

Criteria of the ideal PDT drug are delineated as follows:^'

A. It should preferably be a single substance, or a mixture with constant

composition otherwise.

B. Its synthesis should be straightforward and can be easily scaled up. The

molecular structure should allow easy functionalizations to fme-tune the

biological property.

C. It should have strong absorption between 650 and 800 nm. Light with a

wavelength shorter than 650 nm can not penetrate tissue effectively. On the other

hand, the photosensitizer having the absorption in the region above 800 nm

might not have high enough energy gap between its Ti state and the So state for

singlet oxygen generation.

D. The quantum yields of the ISC as well as the singlet oxygen generation should

be high.

E. The dark toxicity should be minimal and therefore the control of tissue damage

by light dose is ensured.

F. It can be readily formulated with a long shelf hfe.

G. It should possess a good pharmacokinetic profile, including selective

accumulation in diseased tissue and rapid clearance fi-om the body after the

treatment. These features are often linked to the amphiphilicity of the compound. While criteria such as A-C are relatively easy to achieve, others are beyond organic chemist's control and therefore harder to pursue.

1.3.2.3 Second Generation PDT Drugs

As introduced in section 1.1, saturation of one cross-conjugated double bond of porphyrins generates chlorins with the longest absorption band shifting to the 670 to 700 nm region with higher intensity. Both features are highly desirable for PDT. Indeed, chlorin-based photosensitizers are the predominant grouping of second generation PDT drugs. Examples of second generation photosensitizers which either have received regulatory approval or are currently undergoing clinical or advanced preclinical testing are given in Figure 1.3.^^

MeOOC-^^

MeOOc' A.

HO

(OMe) (OH) Tin Etiopurpurln OH BPDMA (Purlytin) m-Tetrahydroxyphenyl chlorin (Visudyne) (Foscan)

Mono-aspartyl chlorin eg Lutetium Texaphyrin (NPeg) (Lutex)

Figure 1.3 Second generation photosensitizer candidates for PDT Benzoporphyrin derivative monoacid ring A (BPDMA), commercially named

Visudyne®, is one of the most successful PDT drugs and was discovered in our groupP It was approved by the FDA in April 2000 to treat "wet" age-related macular degeneration (AMD), an ocular disease commonly occurring to elderly people and resulting in the loss of central

• • 59 Vision.

BPDMA is synthesized by the Diels-Alder reaction between the dienophile dimethylacetylenedicarboxylate (DMAD) and PpIX dimethyl ester, followed by the base- catalyzed rearrangement and the acid-catalyzed hydrolysis (Scheme 1.9).^^

BPDMA (Visudyne)

Scheme 1.9 Synthesis of BPDMA The monoacid final products are far more active in PDT than the diacid counterpart and the starting diester." BPDMA exhibits strong absorption at 686 nm (log £ = 4.54)^^ and its quantum yield for singlet oxygen is 0.46 in v/vo". The concentrations of BPDMA in cancerous tissues are usually higher than in the surrounding healthy tissues, although no specific affmity is confirmed.^^ Moreover, it takes no more than 72 hours for BPDMA to clear fi-om the body after treatment, in contrast to 4 to 6 weeks for Photofrin®.^^

Other approved second generation PDT drugs include m-hydroxytetraphenylchlorin

(trade name: Foscan®, approved in 2001 in EU, Norway and Iceland for the treatment of palliative head and neck cancer) and aminolevulinic acid (ALA, trade name: Levulan®, approved in 2000 in the US for the treatment of actinic keratosis).^^ Different from most photosensitizers for PDT, ALA is a metabolic precursor. After the injection, it interacts with the heme biosynthetic pathway and is converted into PpIX in situ. Therefore, ALA is also designated as the "endogenous porphyrin".^^ The concentration of in situ generated PpIX is found to be much higher in cancerous tissue rather than in healthy tissue.^^ Since the longest absorption band of PpIX is at 630 nm and the irradiation light of the same wavelength penetrates tissue poorly, ALA is mainly used to treat superficial lesions.^^

L3.2.4 Third Generation PDT Photosensitizers and Current Challenges of PDT

The "third generation PDT photosensitizer" is loosely defined and generally refers to the photosensitizer covalently linked to a biomolecule, which has high affinity for a specific target and can hopefully promote the accumulation of the resulting photosensitizer- biomolecule conjugate at targeted tissue.^' A variety of biomolecules have been successfully conjugated to photosensitizers, including: antibodies to target antigens,^''' ''^ cholesterol to improve localization to cell membranes,'^ sex hormones to target cancerous tissue in breasts, ovaries, prostates or testes,^' carbohydrates to improve water-solubility^^ as well as to target the conjugates to recognized cells,^* and oligonucleotides^^ to deliver selective photodamage to targeted DNA or RNA strands. Some examples of photosensitizer-biomolecule conjugates are shown in Figure 1.4.

It needs to be pointed out that for these conjugates, the pharmacokinetic profiles of both the photosensitizers and the biomolecules may be drastically altered once joined as a whole, which often renders the desired affinity or specific targeting motif void.^'

Figure 1.4 Photosensifizer-biomolecule conjugates

Other developments of the PDT drug involves the attachment of a chemotherapeutic agent to a photosensitizer to bring about combined therapeutic effects and increase the lethality of PDT.^^ Two examples of "photochemotherapeutic agents" containing, nitrogen mustard-based DNA-intercalating components are shown in Scheme 1.10.^°'^' The nitrogen mustard agent can readily form a cytotoxic aziridinium ion, which is capable of cross-linking

82

DNA. However, the possible dark toxicity incurred by the chemotherapeutic moiety casts doubt on this strategy.

DNA cross-linking behavior of nitrogen mustard agents

DNA r r - T ^ r \

R ^^Y> ^ DNA ^ DNA Nitrogen mustard aziridinium ion

( R= arvl, all

Scheme 1.10 Potential photochemotherapeutic agents and DNA cross-linking mechanism

Despite having successfully been used to treat some forms of cancers, precancerous lesions and AMD, PDT has some limitations.

The major bottleneck of PDT is the transmittance window between 650 nm and 800 nm, which determines the limited tissue penetration depth (less than 2 cm). For this reason, bulky tumors and metastatic cancer can not be treated by PDT.^^ A new technique using two- photon excitation (TPE) might be the solution to this dilemma, hi TPE, a photosensitizer is excited by simultaneously absorbing two photons of lower energy (longer wavelength, near

IR region) instead of one photon of higher energy, which is advantageous for PDT since IR light can penetrate tissue much deeper.*^' hi addition, as highly focused laser beams are used in TPE, PDT can be performed on a smaller and more confined diseased site, with less out-of- focus damage to healthy tissue.*^'

PDT has two major post-treatment side-effects: the angiogenic effect and the pronounced inflammatory response. The former refers to the regrowth of the tumor or blood vessels from residues and the latter corresponds to the PDT-induced inflammation around the

CO QC treated area. ' The current solutions to these problems involve local or systemic administration of anti-angiogenic agents, immunosuppressive agents or anti-inflammatory drugs before or after PDT.^*'

1.4 Research Objective

The objective of this project is to develop a "photodynamic" site-specific drug delivery strategy, whereby the drug can be released by visible light and only at the site of irradiation. In PDT, the destruction of the photosensitizer itself by singlet oxygen was observed and accounted for part of the photobleaching process.^ We envisioned that such destructive behavior could be exploited in a constructive way, that is, by taking advantage of the singlet oxygen chemistry, especially the [2+2] cycloaddition with alkenes to give carbonyl cleavage products via the dioxetane intermediate (section 1.2), a drug molecule can first be converted to a prodrug moiety and linked to a photosensitizer through a specially designed olefin linkage and later be released upon illumination. In addition to generating of singlet

oxygen via photosensitization, the photosensitizer moiety of the complex can also help to

target the complex to diseased tissue.

Literature regarding the synthetic applications of the [2+2] cycloaddition of singlet

oxygen to olefins is scarce, partially due to generally low chemoselectivity against the "ene"

reaction and the [4+2] cycloaddition. One example can be found in Woodward's total

synthesis of chlorophyll (Scheme Lll).^^ The singlet oxygenation of vinylpurpurin to give

methoxalylpurpurin is a pivotal step in the entire synthesis and a [2+2] cycloaddition followed

by spontaneous dioxetane decomposition is believed to be involved. The high reactivity of the

exocyclic double bond towards the [2+2] cycloaddition can be attributed to the activation

effect of the ring-C nitrogen as a vinylogous enamine nitrogen.

chlorin e6 •NH N==/ trimethyl ester air/hv \\ • (direct "N HN- ^02)59% Steps precursor to Step 39 40-46 chlorophyll)

COzMe Me02C COzMe CO CHO C02Me / COzMe MeOzC 0-^0 Me02C Meo/ COaMe vinylpurpurin methoxalylpurpurin

Scheme 1.11 [2+2] Singlet oxygen cycloaddition reaction in Woodward's total synthesis of

chlorophyll

Another excellent example is Breslow's photocleavable cyclodextrin carrier for PDT

photosensitizers (Scheme 1.12). A hydrophilic cyclodextrin dimer linked by a 1,2-vinyl

disulfide is used as a carrier to bind and solubilize a phthalocyanine-based photosensitizer Upon photoirradiation, the [2+2] cycloaddition of singlet oxygen to the electron rich double bond generates a dioxetane and its simultaneous decomposition releases the photosensitizer.^^'

Scheme 1.12 Photocleavable cyclodextrin carrier for PDT photosensitizer

Different from the aforementioned photochemotherapeutic conjugates (Scheme 1.10) in which a chemotherapeutic moiety remains active and is fixed as part of the complex throughout the entire PDT procedure, our strategy aims to deactivate the drug first by converting it to a prodrug form linked to a photosensitizer and later restoring it to the original structure to regain the bioactivity via cleavage from the double bond linkage with the aid of singlet oxygen. It's noteworthy that, during the drug incorporation and release stages, the photosensitizer moiety only undergoes minor side-chain modifications and its chromophore is barely affected. Therefore the photosensitization capability {e.g. generating singlet oxygen) of the photosensitizer moiety is preserved and itself can be regarded as a normal PDT photosensitizer before and after the drug release. Obviously, the photocleavable double bond linkages of the photosensitizer-drug complexes should be highly activated, such as enol ethers, enamines or vinyl sulfides, to ensure the desired [2+2] cycloaddition chemoselectivity in singlet oxygenation.

The success of this project may lead to valuable medical applications. For PDT, anti- angiogenic or anti-inflammatory drugs can be incorporated with photosensitizers by this system and released at the desired location simultaneously when PDT is performed. As a result, PDT side effects can be limited in a highly efficient way. In fact, not only anti- angiogenic or anti-inflammatory drugs but also other complementary drugs can be dehvered and bring about tandem effects with the photosensitizers. On the other hand, since the [2+2] cycloaddition of singlet oxygen to double bonds is a rapid process, the light dose can be limited to a level just enough for the cleavage of the double bond, which minimizes the imwanted damage to surrounding tissue. Consequently, this system can also work as a "pure" selective drug delivery system and the photosensitizer fragment will be cleared from the body after drug release.

Details regarding the design and synthesis of these photosensitizer-drug complexes will be discussed in the following chapters. CHAPTER TWO

Building Photosensitizer-Drug Complexes Using

Palladium-Catalyzed Cross-Coupling Reactions and

Ruthenium-Catalyzed Alkyne Addition Reactions 2.1 Design Strategy

The first strategy for designing photocleavable porphyrin-drug complexes was inspired by an early porphyrin functionalization reaction developed by our group. More than a decade ago, Boyle et al. introduced the first iodination of porphyrins followed by Pd(0)- catalyzed Sonogashira alkynylation to furnish porphyrin alkyne conjugates (Scheme 2.1).^^ A variety of alkyne moieties including those bearing electron-donating groups (R = alkyl or alkoxyalkyl groups) have been introduced to porphyrins in this fashion.

Ph Ph Ph

R

Ph Ph Ph 11-1 11-2 ll-3-Zn

Scheme 2.1 lodination and Sonogashira alkynylation of 11-1

Since the alkynylporphyrin synthon is readily available, we sought to exploit the versatile alkyne chemistry to rationally design a strategy for complex synthesis and drug release. Ru-catalyzed addition of carboxylic acids to alkynes, as a mild, efficient and non• toxic methodology to produce enol esters, initially looked promising (Scheme 2.2).^'"^^ The commercially available, air- and water-stable ruthenium complex [RuCl2(p-cymene)]2 has proven to be potent for such transformations.^''' Generally, the Markovnikov product predominates in this reaction. However, with the proper choice of base and phosphorus ligands, both the Markovnikov and the anti-Markovnikov products can be generated selectively.^^'

H R2 R-| H [Ru] -R2 + X Ri o^ y-0 R2 R3 OH R3 R3 Markovnikov /anti-IWarkovnikov Products

R-1/R2 = H, akyl, aryl, alkoxyl, R3 = alkyi, aryl, peptide, [Rul = [RuCl2(p-cymene)]2 or other ruthenium complexes,

Scheme 2.2 Ruthenium-catalyzed addition of carboxylic acids to alkynes

Enol esters are important monomers in polymerization reactions. They are also extensively utilized as mild and efficient acylation agents in organic synthesis.^^ As far as our project is concerned, we are particularly interested in their reactions with singlet oxygen, which was reported by Wilson and Schuster.Besides the typical [2+2] cycloaddition and the "ene" reactions, a unique acyl-shifted reaction had also been observed. The singlet oxygenation of enol lactone 11-4, a representative substrate, shows all three reaction modes

(Scheme 2.3). The general product distribution of singlet oxygenation of enol esters depends on substrate structure, solvent and reaction temperature. With the presence of the abstractable allylic hydrogen in substrates, the "ene" product is normally dominant. However, enol ester II-

5 gives mainly the [2+2] cycloaddition product in MeOD upon reaction with singlet oxygen

(Scheme 2.4). "^'^ Scheme 2.3 Singlet oxygenation of enol lactone 11-4

H H

CD30D

o o 11-5 > 70%

Scheme 2.4 Singlet oxygenation of enol ester 11-5

As stated in section 1.4, the [2+2] cycloaddition followed by the decomposition of a

1,2-dioxetane is the foundation of our drug release strategy. Based on the fact'*^'^^'^'^^'^ that

electron-rich olefin substrates favor [2+2] cycloaddition, we expected a more electron-rich 1-

alkoxy enol ester (Figure 2.1) would give predominantly the [2+2] singlet oxygenation product as compared to the aforementioned enol esters.

Figure 2.1 Structure of 1-alkoxy enol ester The first strategy of complex synthesis and drug release is depicted in Scheme 2.5.

DPP 11-1 is first converted to iodoDPP 11-2. lodination rather than bromination is employed based on the fact that iodoporphyrins undergo Pd(0)-catalyzed cross-coupling reactions at a significantly faster rate.^°' 11-2 is then protected by the metallation with Zn(II) before the subsequent Sonogashira coupling with ethoxyacetylene to yield an alkynylporphyrin ll-3-Zn.

After demetallation, the Ru-catalyzed addition of carboxylic acids to 11-6 gives porphyrin- substituted ethoxy enol esters 11-7. This is the "drug incorporation" step and the drugs here are defined as any biologically active molecules containing a carboxyl group. During the drug release stage, highly electron-rich 11-7 is expected to undergo a [2+2] cycloaddition with singlet oxygen and generate dioxetanes 11-8 upon photoirradiation. 11-8 are anticipated to be thermolabile and readily decompose to give a porphyrin-aldehyde 11-9 and mixed carboxylic- carbonic anhydrides (MCCA) 11-10. MCCAs are highly susceptible to hydrolysis with the evolution of CO2 and the incorporated drugs (carboxylic acids) can be cleanly released. The hydrolysis of 11-10 can be further accelerated by hydrolases,''^^ which are ubiquitous throughout the human body. Ph

-NH (F3CC02)2Phl Zn(0Ac)2 I5 -N HN

Ph 11-1

Pd(PPh3)2Cl2, -OEt Cul, EtaN

[Ru] TFA OEt OEt RCOOH (drug) ^

O,

EtOH H,0 CHO ^ R^O^OEt (hydrolase) 002^ 11-10 + RCOOH (drug)

drug incorporation steps

drug release steps

Scheme 2.5 Proposed synthetic roadmap of incorporation and release of bioactive acids Ethoxyacetylene is specifically chosen in this design to facilitate drug release. By providing an ethoxy group, it increases the electron density of the olefin 11-7 and promotes the

[2+2] reaction mode. Consequently, it leads towards the formation of MCCA as photolysate with the subsequent release of the drug.

By the use of this strategy, bioactive carboxylic acids or even N-protected peptides could be transformed and become part of the porphyrin conjugates 11-7. After introduction into the human body and accumulation in desired tissue, visible light irradiation can trigger the singlet oxygenation-decomposition-hydrolysis chain sequence and release the drug locally on demand.

2.2 Results and Discussion of the Original Design

Lindsey's "Two-step, One-flask" protocol"*^' ^'^ for making meso-substituted porphyrins provides two synthetic routes to 11-1 (Scheme 2.6). Dipyrromethanes 11-11 and II-

12 were readily obtained by acid-catalyzed condensation of pyrrole and aldehydes.'

However, the subsequent transformations to 11-1 via route A or B yielded dramatically different results.

Ph

11-1 11-12

Scheme 2.6 Retrosynthetic routes to 11-1 Route A was adapted from Manka and Lawrence's procedure"^ and DDQ was used in place of chloranil in the final oxidation step. Dipyrromethane 11-11 was condensed with benzaldehyde and the following oxidation gave rise to 11-1 in 44% yield. However, under the same reaction conditions (the catalyst, concentration, temperature, etc.), 5- phenyldipyrromethane 11-12 failed to condense with paraformaldehyde. Instead, scrambled porphyrin products of 5,10,15-triphenylporphyrin 11-13 and 5,10,15,20-tetraphenylporphyrin

(TPP) 11-14 were generated in a combined yield of 10% (11-13: 11-14 = 1:2, Route B). Such a difference between the two routes can be attributed to the poor solubility of paraformaldehyde as well as acid-catalyzed dipyrromethane scrambling''^' (Scheme 2.7). The phenyl group once on the 5-position of 11-12 provides resonance stabihzation to the carbocation of 11-15, which can be attacked by 11-12 to generate 11-16, an important building block of 11-13 and II-

14.

11-16

Scheme 2.7 Acid-catalyzed scrambling of 11-12 lodination of 11-1 using the conditions of Boyle et al}^ at room temperature gave rise to a mixture of mono-iodinated and di-iodinated products and the solubilities of the latter in common organic solvents are poor and recrystallization was employed to eliminate the majority of the diiodide contaminants. However, further purification using silica chromatography proved to be tedious and time-consuming. The residual diiodoDPPs, as the first mobile band, streaked on the column and contaminated the remaining fractions. Repeated recrystallization and chromatography cycles were required.

One solution to circumvent the purification problems was thought to be the introduction of iodine at the porphyrin synthesis step. This could be achieved by mixed condensation of dipyrromethanes with two different aldehydes, one of which contains the iodo group and the other bears appropriate substituents to: 1) improve solubility and 2) impose polarity difference among mix-condensed products to facilitate the subsequent chromatography, hideed, porphyrins 11-17 and 11-18 (Figure 2.2) were accordingly produced in reasonable yields and column chromatography proved straightforward, owing to the large

Rf differences among three major porphyrin products. It is notable that BF3-Et20 as the Lewis acid catalyst and DDQ as oxidant are critical to the success of these preparations. On the outer phenyl rings of 11-17 and 11-18, the iodine group is less sterically hindered than that of the we.so-iodinated counterpart, which is advantageous if steric bulk is a serious concern in cross- coupling reactions. 11-17: para-iodo 11-18: meta-iodo

Figure 2.2 Structures of 11-17 and 11-18

Pd(0)-catalyzed cross-coupling reactions, namely the Stille, Suzuki, Heck,

Sonogashira reactions, etc., are among the most powerful and widely used methodologies in

organic synthesis."^ The mild reaction conditions and broad functionality tolerance make

these reactions ideal for preparations and peripheral modifications of porphyrinoids."^ We

were especially interested in Sonogashira and Heck reactions for their simple substrate

requirements; that is, terminal alkynes or alkenes can be directly coupled without prior

transformation.

Due to the facile insertion of Cu(I) into the porphyrin core, porphyrin substrate 11-2

was first metallated with Zn(II), which can easily be removed by acid as required. The

Sonogashira reaction of ll-2-Zn and ethoxyacetylene was carried out following the standard protocol, i.e. Pd(PPh3)2Cl2 as catalyst and EtaN as base in dry THF solution.After 24 hours reaction at room temperature, a trace amount of a less mobile porphyrin product was observed on TLC. ESIMS spectrum of the crude mixture showed an ion peak of 592.2 m/e, corresponding to the protonated ll-3-Zn. However, attempts to improve the yield by increasing the catalyst load or the reaction temperature, were unsuccessful.

We then turned our efforts to test a different substrate, the aryl-iodinated Zn(II)DPP

11-18-Zn. To our disappointment, 11-18-Zn failed to give any coupling product and the starting material was recovered intact by chromatography after 24 hours refluxing in THF.

Since the majority of terminal alkynes which have been introduced to porphyrin periphery by

the Sonogashira reaction are those substituted with electron-withdrawing groups or mildly

electron-donating groups, the highly electron-rich nature of ethoxyacetylene presumably

accounts for the poor reactivity.

Steps subsequent to the Sonogashira reaction in Scheme 2.5 were therefore

suspended and efforts were made to find an alternative way to carry on the project.

2.3 Modifîcation Using the Heck Cross-Coupling Reaction

Heck reactions have been successfully applied to couple electron rich olefins, such as

enol ethers, thioenol ethers, enamines and enamides, with aryl halides."^' Therefore it

seemed plausible to get around the above problem by adding carboxylic acids to ethoxyacetylene followed by the Heck coupling of the resulting ethoxy enol ester to Zn(II)- iodoDPP.

We used benzoic acid to test our idea. Following the literature procediire,^'* benzoic acid was added to ethoxyacetylene using the [RuCl2(p-cymene)]2 catalyst and a completely

Markovnikov-selective product 1-ethoxyvinyl benzoate 11-19 was generated in 80% yield

(Scheme 2.8). 11-19 is highly susceptible to hydrolysis and the following coupling reactions had to be carried out in dry solvents. O [RuCl2(p-cymene)]2 OH + OEt O

11-19

Scheme 2.8 Synthesis of 11-19

The general mechanism for the Heck coupling reaction has been widely accepted to involve catalyst preactivation, oxidative addition, olefin insertion, jS-hydride elimination and reductive elimination steps as depicted in Scheme 2.9, although the details regarding each of these mechanistic steps remain somewhat controversial.'^°' Olefin insertion is the C-C bond formation step and determines the regio- and stereoselectivity of the reaction. While both electronic and steric effects govern the regioselectivity, the steric effects normally dominate and favor /S-arylation.'^° In our case, 11-19 is a highly electron-rich 1,1-disubstituted terminal alkene. Although the electronic effect initially favors the attack of the organopalladium on the /3-carbon, the lack of /S-hydrogen to eliminate could shift the equilibrium towards i8-arylation in the absence of alternative elimination pathways. Therefore, the desired /3-arylation product 11-7-Zn is expected to be the only coupling product after the reaction. Pd(0) or Pd(ll) pre catalyst preactivation

H

Scheme 2.9 General mechanism of the Heck cross-coupling reaction

Our first attempt of the Heck reaction between ll-2-Zn and 11-19 employed

Pd(PPh3)2Cl2 as the catalyst and EUN as base.'^^ After a reflux procedure in dry THF for 16

hours, two porphyrin products appeared on TLC. The major product ll-20-Zn had a similar Rf

value to the starting porphyrin while the other product 11-21-Zn was much less mobile on

TLC and was produced in small amount. Continued refluxing for a total of 48 hours gave no

improvement of yields. The crude reaction mixture was chromatographed on silica to furnish

ll-20-Zn and 11-21-Zn in 28% and 5% yields respectively. Most of the starting olefin 11-19

and about two-thirds of the ll-2-Zn were recovered, which clearly showed that the expected

cross-coupling reaction did not occur. The two porphyrin products were characterized using

NMR and MS. ll-20-Zn turned out to be the deiodination product and the structure of 11-21-

Zn was not identified until its X-ray crystal structure was solved (Scheme 2.10). The structure and catalytic studies of 11-21-Zn will be discussed in the next section.

Ph Ph Ph Ph not produced ll-2-Zn ll-20-Zn 11-21-Zn \ ll-7-Zn ^

Scheme 2.10 Heck coupling using Pd(PPh3)2Cl2 as the catalyst

Due to the isolation of halogen-exchanged oxidative addition intermediate 11-21-Zn, the failure of the reaction can probably be attributed to inefficient olefin coordination or olefin insertion due to steric repulsion. Unlike other well-defined organic reactions. Heck reactions are somewhat unpredictable and sensitive to the variations of reaction conditions.'^'' 11-19 has hitherto never been used as an olefin substrate in Heck reactions. To better evaluate the reactivity of 11-19, we used iodobenzene instead of 11-2-Zn and experimented with various compositions of catalyst "cocktails".

Pd(OAc)2-P(o-Tol)3 system is reported to be highly potent in the Heck arylation of olefins.However, the Heck reactions between iodobenzene and 11-19 using Pd(OAc)2-P(o-

Tol)3 as the catalyst, NaOAc or K2CO3 as base, at 80 °C to 130 °C in DMF did not give any coupling product, even with the addition of the phase-transfer agent «Bu4NI.'^^

We have also tried the PCP pincer catalyst PdCl[C6H3-2,6-(OPPr'2)2], which is highly efficient in catalyzing arylation of some 1,1 disubstituted alkenes to generate trisubstituted alkenes,'^^ but the coupling reaction did not occur. Based on the unsuccessful results with a number of typical Heck catalyst formulas, II-

19 seems unreactive towards the Heck coupling and efforts to screen more catalytic systems were abandoned.

2.4 Structure Characterization, Formation Mechanism and Catalytic Studies of II-

21-Zn

2.4.1 Structure Characterization of 11-21 -Zn

A single crystal of 11-21-Zn was obtained by slow diffusion of hexane into its DCM solution. X-ray crystal structure determination showed two independent molecules A and B and a co-crystallized solvent molecule (DCM) in the unit cell (Figure 2.3). Each molecule displays a slightly ruffled porphyrin macrocycle a-bonded through its me^o-carbon to the

Pd(II) atom, which is in square planar coordination geometry. The porphyrin core of the molecule A is more distorted than that of the molecule B as the maximum deviations from the

25-atom mean planes are 0.320 Â for A and 0.258 Â for B. Figure 2,3 An ORTEP drawing of 11-21 -Zn showing thermal ellipsoids at 50% probability

level (top view). Solvent molecule (CH2CI2) and H atoms have been omitted for clarity

Molecules A and B differ most distinctly by the relative orientation of two cross phenyl substituents on porphyrin. As shown in Figure 2.4, they are staggered relative to each other in the molecule A while parallel relative to each other in the molecule B. The dihedral angles between the mean planes of porphyrins and two meso- phenyl rings are 52.8° and 79.6° in the molecule A and 64.8°, 64.9° in the molecule B. Some important geometry parameters for molecules A and B are summarized in Table 2.1. Molecule A Molecule B

Figure 2.4 An ORTEP drawing of 11-21-Zn showing thermal ellipsoids at 50% probability

level (side view). Solvent molecule (CH2CI2) and H atoms have been omitted for clarity

Table 2.1 Selected bond lengths and bond angles for molecule A and B of 11-21 -Zn

Molecule A Molecule B Interatomic distances (Â) ; Pd(l)^(l) 2.324(2) I Pd(2)-P(4) " ^ [2.327(2) ' :P(j(l).p(2)" :2.329(2)r"Pd(2)^P(3)"""""" |2337(2)^'""\ Pd(l)-Cl(l) ' 2.384(2) ^ Pd(2)-Cl(2)" ' ' 2.377C2) ; I Pd(l)-C(10) • 2.039(9)^ I Pd(2)-C(82) " F 2;008(10) ' Bond angles ( ° ) C(10)-Pd(l)-P(l) ^^-9(3) nC(82)-Pd(2)-P(4) ^^f 89^7(3) j

(X10)-Pd(l)^P(2) i 87^(3) I Qg2):pd(2)-T^(3y^ " [ -^-^^^^^ I P(l>-Pd(l)-^1(1) 92.36(9) P(4)-Pd(2)-CK2) " ' 91^45(9) j rP(2>^l)-Cl(l) 90^87(9)^" i P(3)Ipd(2)^Cl(2) T 9GL59(9) \ P(l)-Pd(l>T'(2) " 176.73(9) Pt4)-Pd(2)^P(3) ' 177^9(9) | ; C(10)-Pd(l)-Cl(l) 178.6(3y^ ' C(82)-Pd(2)-Cl(2) ^ 178^3) ~ ^ The 'h NMR spectrum of 11-21-Zn with peak assignments is shown in Figure 2.5.

The high electron density of the meso-honded Pd atom causes the upfield shifts of most porphyrin peripheral hydrogen signals, compared to those of ll-20-Zn. As illustrated in the crystal structures (vide supra), two phenyl rings, one from the top PPh3 and the other from the bottom PPh3, overshadow part of the porphyrin plane in a "sandwich-like" manner. As a result, the phenyl hydrogen signals of two PPh3 ligands of 11-21-Zn shift 0.5 ppm upfield for ortho-

Hs (multiple peaks at 7.2 ppm) and 0.95 ppm upfield for meta-Rs and para- Hs (multiple peaks at 6.5 ppm) compared to those of /ra«5-Pd(PPh3)2Cl2, due to the shielding effect of the porphyrin core.

^eta-para 1

meta-para2

ortho2

meta-para2

ortho2 meta-para1

pi M P3 P2 orthol ! meso

rn purities

10.00 9.50 9.00 8.50 8.00 7.50 ppm (t1)

Figure 2.5 'H NMR spectrum of 11-21 -Zn (CD2CI2, 400 MHz) The ^'P NMR spectrum of 11-21-Zn in CD2CI2 shows a singlet at 24.5 ppm, which confirms the trans relationship of the two PPh3 ligands.

The ESIMS spectrum of the 11-21-Zn shows a family of cluster peaks corresponding to the proposed structure. This is a characteristic feature for metallic compounds with complex isotope distributions. Apeak of 1190.1 m/e corresponds to the cation of 11-21-Zn and the peaks of 1154.9 m/e and 893.0 m/e peaks correspond to the molecular cations after losing a chloride or a PPha ligand.

The electronic absorption spectra of 11-21 -Zn, ll-20-Zn and the starting material 11-2-

Zn are shown in Figure 2.6. The Soret bands and Q-bands of these three ZnDPP derivatives show a trend of red-shift in the ascending order of non-substituted il-20-Zn < iodo-substituted

11-2-Zn < palladium-substituted 11-21-Zn. ll-20-Zn 1.50-, 11-21-Zn ll-2-Zn

1.25-

1.00- c o

o 0.75- < 0.50-

0.25-

0.00 I 400 450 500 550 600 650 Wavelength (nm)

Figure 2.6 UV-Vis spectra of 11-2-Zn, ll-20-Zn and 11-21-Zn

2.4.2 Mechanism of the Formation of 11-21 -Zn

Twei'o-Palladioporphyrin was first discovered'by Arnold and co-workers in 1998 and a number of we^o-palladioporphyrins have been generated by the same group through the oxidative addition of bromoporphyrins onto the Pd(0) compounds such as Pd(PPh3)4 and

Pd2(dba)3'^''"'^^. One of the products has been characterized by X-ray crystallography,''^'' showing that a bidental phosphine Hgand (dppe) chelates the Pd center in cw-coordinated square planar geometry. Our crystal structure of 11-21-Zn is the first one with the most common PPh3 ligand. Moreover, instead of the one-step stoichiometric preparation, 11-21-Zn was isolated as an intermediate fi-om a reaction system wherein a Pd(II) species was employed on a catalytic scale. The conversion of the Pd(II) catalyst into 11-21-Zn presumably consisted of three mechanistic steps: 1) in situ reduction of the Pd(PPh3)2Cl2 to Pd(0) species; 2) oxidative addition of ll-2-Zn onto the Pd(0) and; 3) halogen-exchange of the chloride for the iodide. The isolation of 11-21-Zn evidently supported the general assumption that Pd(II) catalysts, such as Pd(PPh3)2Cl2 and Pd(0Ac)2, are pre-reduced to Pd(0) before they enter the catalytic cycles of cross-coupling reactions. We were prompted to study the formation mechanism and the catalytic activity of 11-21-Zn in our reaction system.

Despite the significance, the detailed mechanism of the in situ reduction of Pd(II) catalysts in cross-coupling reactions has not been unambiguously established. More importantly, small variations of catalysts, Hgands, base or solvent in different reaction systems often dictate different mechanism pathways and one unified mechanism for the reduction of all Pd(II) species is not likely to be found.

Amatore et al. used electrochemical methods and ^'P NMR spectroscopy to study the in situ reduction of Pd(0Ac)2 in the presence of PPhs and proposed that the coordinated PPh3 reduces the Pd(II) by an intramolecular process, which is initiated by the attack of the acetate ligand (Scheme 2.11).'^^' Ozawa and Hayashi's study of the reduction of Pd(0Ac)2 in the presence of BINAP, Et3N and water agrees with Amatore's mechanism, although a significant effect of water content on the progress of the reduction was observed.'^^ In fact, phosphine

(e.g. PPh3) has been generally regarded as the reductant in most of phosphine-involved Pd(II) catalyzed reaction."^ Amatore's mechanism generally works well when phosphine ligands and oxygenated species are both present in reaction systems.

PPh3 + Pcl(0Ac)2 + 2PPh3 AcO OAc Pcl°(PPh3)(0Ac)- + AcO-PPh3

AcO. AcOH + 0=PPh3 + HO AcO-PPhg

AcO. ,PPh3 AC2O + 0=PPh3 AcO

Scheme 2.11 Mechanism of the in situ reduction of Pd(0Ac)2

In contrast, the mechanism of the reduction of Pd(II) catalysts without oxygenated species, such as Pd(PPh3)2Cl2, remains controversial. Amines, such as triethylamine, ethyldiisopropylamine, etc., were reported to reduce Pd(PhCN)2Cl2 with a mechanism shown in Scheme 2.12.'^^ EtaN first coordinates to the Pd center and the a- or /3- C-H bonds of the amine become activated. After the insertion of the Pd into one of these C-H bonds, two subsequent reductive eliminations give the Pd(0). This mechanism is evidently supported by the isolation of the Pd(0) and an enamine-palladium complex, which was characterized by X- ray crystallography. Interestingly, Grushin and Alper''''' observed that rigorously dried EtsN

(freshly distilled from sodium) failed to reduce Pd(PPh3)2Cl2. However, after the deliberate addition of a ten-fold excess of water, the expected reduction occurred. It was suggested that

PPh3 reduces Pd(PPh3)2Cl2 with the assistance of OH", which came from the deprotonation of water. It was also postulated that the residual water in amines should be sufficient to account for the stoichiometric demand of OH' in the in situ reduction scenarios, considering the Pd(II) species is used on a catalytic scale. Such a mechanism is similar to Amatore's except for the replacement of acetate for hydroxide. Interestingly, another investigation shows that freshly distilled and dried EtsN reduced PdCl2(P(OPh)3)2 in 30% yield and the yield was improved to ca. 60% after the addition of water.'^^ Furthermore, it was confirmed that both the amine and water participated in the reduction by an isotope effect study using deuterated water and

EtsN.'^^ Other suggested in situ reductants of Pd(II) species in cross-coupling reactions include olefins (in the Heck reactions) or even solvent molecules, although less popular.'^'^

C-H H ^NEt2 9' Et,N insertion^ ^ .NEtz CI—Pd-CH2 L-Pd-L CI—Pd-NEt2 Ci-P|d-C^H I CI -L CI -L CI H3C Ci CH3 C-H insertion at /^-position is also possible

EtsN reductive elimination^ + HNEta CI reductive elimination P-elimination Pd(0)L2 Cl-Pd-L .NEt2 +L L-Pd-C^H H HNEtaCI EtgN CH3 NEt,

L=PhCN triethylamine shown as the representative amine, mechanisms involved other amines are similar

Scheme 2.12 The reduction of Pd(PhCN)2Cl2 by EtaN

It is generally difficult to study such in situ reductions by directly monitoring the

Pd(0) products. For the reaction systems without stabilizing phosphine ligands, the newly- generated Pd(0) can readily precipitate out as "palladium black" or be converted into catalytically active nanoparticles (colloids), providing appropriate sol stabilization methods are used.'^°' On the other hand, for systems with phosphine ligands (like our reaction system), Pd(0) can be stablized by these ligands against sediments while remains reactive towards oxidative addition. Despite that oxidative addition products can be further transformed or reduced, we believed we could study the in situ reduction at least qualitatively by trapping the reduction product (Pd(0)) with aryl bromides or iodides and monitoring the oxidative addition products and their derivatives.

In our original Heck reaction between 11-2-Zn and 11-19, leading to the isolation of II-

21-Zn, the only possible reductants could be PPha, EtsN, THF, the olefin itself (11-19) or the combination of any of the above with trace water. A series of control experiments have been conducted to screen the critical reagent responsible for the reduction of Pd(PPh3)2Cl2 in our system, as summarized in Table 2.2. All the reactions were run at the same temperature for the same period as the original reaction, which is included as entry 1 for comparison. In the first trial, we increased Pd(PPh3)2Cl2 fi-om 0.5 to 1 equivalent and eliminated the olefin substrate (entry 2, Table 2.2). After the reaction, TLC showed a similar product distribution to entry 1 and purification by chromatography gave 11-21-Zn and ll-20-Zn in slightly improved yields. This clearly ruled out the possibility of the olefin being the in situ reductant. The low isolated yields of 11-21-Zn in entries 1 and 2 are due to the fact that we^o-palladioporphyrins such as 11-21-Zn are unstable in solution and upon silica gel chromatography.'^'' They readily decompose to give hydrodepalladation products (ll-20-Zn in this case).'''^ Nevertheless, the combined yields of 11-21-Zn and ll-20-Zn in entries 1 and 2 indicate the in situ reduction of

Pd(PPh3)2Cl2 had occurred substantially. Table 2.2 Control experiments to study the in situ reduction of Pd(PPh3)2Cl2

Reagents Products Entry /Pd(PPh3)2Cl2: ll-2-Zn Olefin TEA" THF* ll-20-Zn'^ 11-21-Zn' 0.5:1 1 eq. 2eq.(A) B 28% ; " 5% 2 1:1 no leq.(A) B 50% 8% 3 1:1 no no ;A no no " 4^ ^l:f" no 5eq.W " B; no no " Equivalents are relative to ïl-2-Zn. Two different sources of EtsN were used: A. commercial reagent (99.5%) with residual water; B. vigorously dried and distilled from sodium. * Two different sources of THF were used: A. commercial reagent (99.5%) with residual water; B. vigorously dried and distilled from sodium. " Yields were determined by NMR. '' Isolated yields. Original conditions are listed for comparison.

We examined the reducing capability of PPh3 by removing Et3N from the reaction

system and using a commercial THF solvent containing residual water (entry 3, Table 2.2).

After the reaction, neither ll-20-Zn nor 11-21-Zn was detected on TLC and the starting 11-2-

Zn remained intact, ft is notable that although the Rf values of ll-20-Zn and 11-2-Zn are close

to each other despite eluant, only ll-20-Zn shows fluorescence on TLC upon 365 nm UV

irradiation, which allows the clear discrimination between them. In addition, the ESI mass

spectrum of the crude reaction mixture didn't show peaks for either ll-20-Zn or 11-21-Zn.

However, adding one equivalent Et3N to this system immediately gave ll-20-Zn and 11-21-Zn,

as detected by TLC. These results ruled out the possibilities of PPha or its combination with

residual water as the reductant in our system. They also confirmed the critical role of Et3N in

the reduction.

Interestingly, when rigorously dried Et3N and THF (both freshly distilled from

sodium) were employed, neither ll-20-Zn nor 11-21-Zn was detected (entry 4, Table 2.2).

Therefore, Et3N alone can't reduce Pd(PPh3)2Cl2 effectively without the assistance of water.

Although this result is parallel to Grushin's observation {vide supra), difference between our

control experiments and their experiment suggest a new vision of the role of water. In Grushin's experiment, excess water was employed and water was suggested to be involved stoichiometrically as the source of hydroxide, which was believed to attack phosphine and initiate the reduction process.'^'' However, in our experiments where reduction occurred substantially (entries 1 and 2), the only possible water source was the residual water in the commercial 99.5% EtsN, which is far from sufficient to account stoichiometrically for the yield of 11-21-Zn and ll-20-Zn. Therefore, it is reasonable to establish that the Pd(PPh3)Cl2 is in situ reduced by EtaN and the reduction is catalyzed by residual water in the reaction system.

The direct oxidative addition product of ll-2-Zn to Pd(0) should be porphyrinyl palladium(II) iodide ll-22-Zn. However, 11-21-Zn was exclusively isolated from our reaction

(entries 1 and 2). To determine whether the halogen exchange occurred during purification procedures or immediately after the oxidative addition reaction, we synthesized an authentic sample of ll-22-Zn (Scheme 2.13). The differences of 'H and ^'P NMR spectra between these two similar compounds allow the clear discrimination between them. We then used NMR to monitor different stages of the reaction and no ll-22-Zn was detected at any of these stages.

This indicates the I-Cl exchange occurred immediately after the oxidative addition through a fast equilibrium, which confirms Grushin's discovery that chloride can replace the iodide of the phosphine-ligated organopalladium(II) complexes readily and rapidly.On the other hand, Br-Cl exchange between porphyrinyl palladium(II) bromides and chlorinated solvents was reported.'^^ To further confirm the chloride source, we stirred a diluted DCM solution of ll-22-Zn for one week and only 15% I-Cl exchange was observed by NMR. It is therefore obvious that the chloride of 11-21-Zn came from Pd(PPh3)2Cl2 after the in situ reduction.

Indeed, a complete I-Cl exchange was achieved 10 minutes after vigorously mixing a DCM solution of ll-22-Zn with an aqueous solution of KCl. ll-2-Zn ll-22-Zn

Scheme 2.13 Synthesis of ll-22-Zn

2.4.3 Catalytic Study of 11-21 -Zn

Unhke 11-19, the highly reactive ethyl acrylate was coupled with 11-2-Zn using the

Pd(PPh3)2Cl2/Et3N system to give ll-23-Zn in 90% yield (based on 72% conversion) after 16 hours reflux in THF (Reaction A, Scheme 2.14). Stoichiometric reaction between 11-21-Zn and ethyl acrylate gave ll-23-Zn quantitatively within one hour (Reaction B, Scheme 2.14).

While employed on a catalytic scale (0.1 eq.) in the coupling reaction of 11-2-Zn and ethyl acrylate under the similar conditions, 11-21-Zn catalyzed the reaction with the same level of efficiency as the original catalyst Pd(PPh3)2Cl2 (92% yield based on 63% conversion.

Reaction C, Scheme 2.14). It is noteworthy that no ll-20-Zn was detected in any of these reactions, showing that the hydrodepalladation of the oxidative addition product (or its halogen-exchange derivative) was completely suppressed. These results clearly established the role of 11-21 -Zn as an active intermediate in the Heck reaction. ll-2-Zn:olefin:Pd(PPh3),Cl,:Et3N = 1:1.2:0.1:2 refluxed for 16 hours conversion: 72% isolation yield based on conversion: 90%

11-21-Zn:olefin:Et3N^ 1:2:2 B refluxed for 1 hour quantitative yield

ll-2-Zn:olefin:||-21-Zn:Et3N = 1:2:0.1:2 refluxed for 16 hours conversion: 63% isolation yield based on conversion: 92%

Scheme 2.14 Catalytic Study of 11-21 -Zn

2.4.4 Insights into the Reaction Mechanism

Our studies of 11-21-Zn gave new insights into the mechanism of the cross-coupling reactions using Pd(PPh3)2Cl2/Et3N system, hi fact, this system is more frequently employed in

Sonogashira, Suzuki, and Stille reactions rather than in Heck reactions. A modified mechanism diagram is proposed in Scheme 2.15. Pd(PPh3)2Cl2 is in situ reduced to Pd(0) by

Et3N with the assistance of trace water, accompanied by the extrusion of fi'ee chloride, which can readily replace the iodide of the oxidative addition products to generate organopalladium(Il) chlorides. In the absence of active olefin or organometallic substrates, organopalladium(Il) chlorides and iodides readily decay by hydrodepalladation. However, when active olefins or organometallic species are added into the system, the catalytic cycle can be resumed to produce the final coupling products and regenerate Pd(0), therefore continuous turnovers are assured.

_^ early-stage mechanistic steps PdL2Cl2 proposed by current study Heck reaction steps - 2Cr EtsN (trace water)

-»• other cross-coupling reaction steps

Ar-R' oxidative addition ArH ^4 hydro• depalladation

ArPdCILs halogen exchange

reductive elimination

R'MX' transme ta Nation

MXX'

L = PPhg, M = Cu, B, Sn, Zn, Mg..., R = alkl, aryl, R' = alkynyl, alkenyl or aryl, X = CI,I, X' = halides

Scheme 2.15 Insights into mechanisms of cross-coupling reactions using Pd(PPh3)2Cl2/Et3N system 2.5 Summary

Our attempts to combine bioactive carboxylic acids with porphyrins to build

photocleavable porphyrin-drug complexes by using palladium-catalyzed cross-coupling

reactions and ruthenium-catalyzed addition of carboxylic acids to alkynes failed. However, an

interesting reaction intermediate 11-21-Zn was isolated from an unsuccessful Heck coupling reaction. Its structure was characterized by X-ray crystallography, NMR and MS. The studies of its formation mechanism and catalytic activity gave new insights into the mechanism of cross-coupling reactions using the Pd(PPh3)2Cl2/Et3N system. CHAPTER THREE

Building Photosensitizer-Drug Complexes with the

First Generation Linker Using Takai Alkylidenation 3.1 Olefînation of Carboxylic Acid Derivatives Utilizing Titanium Reagents^^'

Olefination of carbonyl compounds is one of the most valuable framew^ork-building

reactions in organic synthesis. Since its discovery in 1953,''*'' the Wittig reaction'"' and its

variants including the Homer-Wadsworth-Emmons reaction,'''^ the Peterson reaction,''''' and

the Julia reaction'""* have been extensively employed in organic transformations. However,

these methodologies suffer one common disadvantage: the carbonyl compound substrates are limited to aldehydes and ketones. Attempts to alkylidenate carboxylic acid derivatives using these reactions generally lead to the undesired acylation of the carbanions. The successful alkylidenation of carboxyhc acid derivatives will generate highly valuable heteroatom- substituted olefins, such as enol ethers and enamines, which are of great importance to our project. The development of this methodology is reviewed as follows.

3.1.1 Tebbe, Grubbs, and Petasis Reagents

The first milestone was reached in 1978, when Tebbe discovered a titanium- aluminium metallacycle III-1 for the methylenation of carbonyl compounds.'''^ III-1 was generated from titanocene dichloride and trimethylaluminium in toluene. After the treatment with pyridine, was converted to methylenetitanocene III-2, which is a Schrock-type'^^ titanium-carbene complex with a high reactivity towards multiple bonds, such as those of alkenes, alkynes, as well as carbonyl functionalities (Scheme 3.1). .Cl AIMea ^A) pyridine Cp2Ti\ Cp2Ti—CH2 Ci PhMe Me -MezAiCI IIM III-2 (Tebbe Reagent) O A

Cp2Ti-0

Ri R2 - Cp2Ti=0

Scheme 3.1 Carbonyl methylenation using the Tebbe reagent

A variety of carbonyl compounds, especially carboxylic acid derivatives including esters, lactones, amides, imides and thiol esters, have been methylenated to give terminal olefins by the Tebbe reagent III-1 in good yields.''*'' In addition to the Lewis acid character and the susceptibility towards water and air, the major limitation of the Tebbe reagent is that it only works for methylenation. Replacement of trimethylaluminium with triethylaluminium did not lead to ethylidenation.'''^

can be transformed through a reaction with isobutene and a Lewis base to the air-stable titanacyclobutane III-3 (the Grubbs reagent), which is readily converted to III-2 by thermolysis and can subsequently methylenate carbonyl compounds (Scheme 3.2).'''^

Methylenation

III-3 III-2 (Tebbe Reagent) (Grubbs Reagent)

Scheme 3.2 Synthesis of the Grubbs reagent Another Tebbe reagent variant is dialkyltitanocene III-4 (the Petasis reagent), which is synthesized by the reaction of titanocene dichloride and alkylithium''*^ or alkylmagnesium chloride.''*^ III-4 is relatively stable to both air and moisture and furnishes the methylenation products (R = methyl) upon heating to 60-75 °C with carbonyl compounds in THF or toluene

(Scheme 3.3).

RLi R CpgliClj CpzTi: Cp2Ti=\^, _^ Methylenation or RMgCI R - RH (alkylidenation) III-4 III-5 (Petasis Reagent) R = Methyl, benzyl,cyclopropyl, -CHjTMS, -CI-I2TES

Scheme 3.3 Synthesis of the Petasis reagent

Applications of the Petasis reagent in alkylidenation are limited to benzylidenation, cyclopropylidenation and silylmethylidenation. This is due to the fact that the important intermediates, alkylidenetitanocenes III-5 are generated by the a-elimination of III-4 and an alternative jS-elimination pathway dominates when dialkyltitanocene precursors bearing (3- hydrogens are employed.

Compared to the Tebbe reagent, both the Grubbs and Petasis reagents provide aluminium-free pathways to III-2 and therefore can be applied to the reactions involving acid- sensitive substrates. However, applications of these reagents are essentially limited to methylenation only and a general while convenient carbonyl alkylidenation methodology would be more desirable. 3.1.2 Takai Alkylidenation

In 1978, Takai et al. reported an effective carbonyl methylenation method using the

CH2Br2-Zn-TiCl4 system.'^' Based on this discovery, they further developed a simple and

general alkylidenation methodology for esters,'^^ amides'^^ and other carboxylic or carbonic

acid derivatives'^^' in the late 1980s. The reaction system involves 1,1-dibromoalkane, Zn,

TiCU and N,N,N',N'-tetramethylethylenediamine (TMEDA) in THF or THF-DCM mixed

solvent. The alkylidenation generally exhibits high Z-stereoselectivity (E-selectivity for amide

substrates only) and proceeds in moderate to high yields (Scheme 3.4).

Zn, TiCU O TMEDA Ri^YR2 X THF or Ri YR2 THF+ CH2CI2

.Y= O, N,S

Scheme 3.4 Takai alkylidenation of carboxylic acid derivatives

Despite wide applications in organic synthesis since its debut, the mechanism of

Takai alkylidenation remains obscure. It has recently been proposed that the TiCU is reduced to a mixture of reactive Ti(II)'^^ and Ti(III)'^^ species (Figure 3.1), with which the dibromoalkane is converted to a Schrock-type titanium-carbene complex or a geminal dimetallic (Ti-Zn) compound as the alkylidenation agent (Scheme 3.5).'^^ Interestingly, PdCh, a trace impurity commonly found in the commercial zinc reagent, is found to be critical to the success of alkylidenation.'^^ Therefore, a catalytic amount of PdCb is dehberately added in practice. Nevertheless, the role of PdCh is still not clear. It has been suggested as an accelerant for the formation of the Ti(III) complex'^^ or for the generation of the dimetallic compound.'" A definitive experimental procedure of Takai alkylidenation has been published in "Organic Syntheses" as one of the standard synthetic techniques.'^^

Figure 3.1 Reactive low-valent titanium species

Br "Ti(ll)" / TiL„ \ Alkylidenation Br R Zn R LnM R

\ M=Tir,r7M=Ti or Znn /

Scheme 3.5 Reaction intermediates in Takai Alkylidenation

Takai alkylidenation also works for diiodoalkanes although the yields are generally lower.'^^ Due to the nucleophilic nature, alkylidenation of esters or amides fails in the presence of aldehydes or ketones. The functional group tolerance of the carboxylic acid derivative substrates includes ethers (including benzyl ethers), alkenes (including terminal alkenes), acetals (including glycosides and dimethyl acetals), silyl ethers, and halides

(including aryl and vinyl halides).'^^ Pivalate esters, formate esters, and o; |8-unsaturated thioesters are reported to be poor Takai alkylidenation substrates.'^^ N-acyl piperidines are the only reported amide substrates. For the aliphatic N-acyl piperidines, the enamine products often undergo tautomerization to give double-bond shifted products via iminium salt intermediates.'^^On the other hand, THP acetals'^^ and silyl groups'^° are tolerable on dibromoalkanes substrates.

As a well-established methodology, Takai alkylidenation provides a simple one-pot and stereoselective protocol to alkylidenate carboxyhc and carbonic acid derivatives, albeit the dibromoalkane substrates are relatively hard-to-access.

3.1.3 Takeda Alkylidenation

A new carbonyl alkylidenation methodology using a thioacetal-Cp2Ti[P(OEt)3]2 system was introduced by Takeda et al. in 1997 with a mechanism illustrated in Scheme

144,161 -pj^g ^.^ ^^.^^ reduction of Cp2TiCl2 with Mg in the presence of P(0Et)3 and drying agent (4Â molecular sieves) gives Cp2Ti[P(OEt)3]2 III-6. The oxidative addition of the thioacetal substrate to III-6 gives the alkyltitanium species III-9. After the addition of a second molecule of III-6, III-9 is transformed by reductive desulfurization to the alkylidenetitanocene

III-5, which readily alkylidenates carbonyl compounds via the oxatitanacyclobutane 111-10 intermediate.

Cp2TiCl2

P(0Et)3 Mg. 4Â molecular sieves

Cp2TI[P(OEt)3]2 SR' CP2T1'' III-6 III-6 R'^TiCpz R^SR' R SR' - TiCp2{SR')2 III-9 III-5 O X Ri^YR2 R'= Ph (III-7), or ^ YR, CP2TI-O III-8 -YR, Y= C, O, S, N - Cp2Ti=0 R

HMO

Scheme 3.6 Takeda alkylidenation using the thioacetal- Cp2Ti[P(OEt)3]2 system It is critically important to choose proper thioacetals as the carbene complex precursors since no III-5 can be generated from a dialkyl thioacetal.''"' In most cases, diphenylthioacetals III-7 are the only thioacetals of choice, except for the making of o;/?- unsaturated alkylidenetitanocenes, where a 1,3-dithiane III-8 maybe used.

A wide range of carbonyl compounds including ketones and aldehydes,'^' esters and lactones,'^' thioesters,'^^ and amides'^^ have been alkylidenated using this methodology. The stereoselectivity is only modest and not manifestly correlated to the bulkiness of the substitutents.'^^ Generally E-selectivity is observed in the alkylidenation of aldehydes and ketones, while Z-selectivity is found in the alkylidenation of carboxylic acid derivatives including amides,'^^ which is in direct contrast to the E-selectivity of the Takai alkylidenation of amides. Both intermolecular and intramolecular alkylidenations have been reported although the success of the latter is often structure-dependent and in low to moderate yields.The functionality tolerance of the carbonyl substrates as well as of the thioacetals has not yet been completely established, although silyl groups'^^' and double bonds

(internal and terminal)'^^ in thioacetals are reported to be tolerated.

111-5 is also found to be reactive towards a variety of multiple bonds such as the C-C double bond, C-C triple bond and C-N triple bond. There are three reaction types between III-

5 and olefins: 1) metathesis'^^"'^' to give a new olefin with the extrusion of methylenetitanocene, 2) /3-elimination'''^' to give the carbenoid insertion product, and 3) reductive elimination'''^"'''^ to give cyclopropanes as shown in Scheme 3.7.'^^ It is noteworthy that the presence of the olefin moieties in thioacetals did not seem to impede the carbonyl alkylidenation (vide supra) and the olefin products obviously survive the alkylidenation reaction conditions. The reactions between 111-5 and alkynes generate conjugated dienes.'^'' Ketones are produced from the reactions between III-5 and nitriles after hydrolysis. 178

CpjTrr ^—' + Cp2Ti= R R' R metathesis/

^R' yg-elimination ^ Cp2Tj~^^ CpzT - TiCp2^ R TiCp2 + R III-5 R H R R' reductive elimination Cp^ - TiCp;

R R' R R-

Scheme 3.7 Reactions of III-5 and olefins

Compared to the previously mentioned alkylidenation (or methylidenation)

methodologies, Takeda alkylidenation is advantageous in terms of the easy-to-access

thioacetal starting materials and the versatility of handUng a wide range of carbonyl

compounds. However, the use of excess titanocene and triethylphosphite is the major

drawback.

Takeda and coworkers have also tested other compounds as the carbene precursors

rather than thioacetals. For example, 2,2-bis(phenylthio)propane, a thioketal, was found to be

able to alkylidenate ketones and give tetrasubstituted olefins under the similar reaction

conditions.'^' However, sterically bulkier thioketals rather give alkenyl sulfide instead.''^ The problem can be solved by using a gem-dichloride to replace the thioketal in the alkylidenation

system. Indeed, a number of tetrasubstituted olefins and trisubstituted enol ethers have been synthesized in moderate yields and the reaction is believed to proceed via a alkylidenetitanocene or a geminal dimetallic intermediate similar to the thioacetal-

Cp2Ti[P(OEt)3]2 system (Scheme 3.8).'^^ Interestingly, a gem-dibromide is less effective than a gew-dichloride regarding this transformation but the reason is unclear.

Cp2TiCl2

P(OEt)3 Mg, 4A molecular sieves

Cp2Ti[P(OEt)3]2 CI CI X CP2T -0 III-6 R3 YR4 X Rv -YR4 Ri TiCp2 R2R3

CICp2Ti TiCpaCI - Cp2Ti=0 or .YR4 Ri Y= C. O

Scheme 3.8 Takeda Alkylidenation using ge7n-dichloride-Cp2Ti[P(OEt)3]2 system

Moreover, mono-halides possessing at least two alkyl substituents on the /3-carbon

can be converted to alkylidenetitanocenes and subsequently alkylidenate carbonyl

compounds.The proposed reaction mechanism is shown in Scheme 3.9.

Disproportionation of two alkyltitanium species 111-11 affords the dialkyltitanocene 111-12, which undergoes an a-elimination to generate the alkylidenetitanocene and consequently

affords the olefination products upon reactions with carbonyl compounds, hi fact, 111-12 has the same structure as the Petasis reagent, although the current method provides a different

approach to it. The exceptional preference of the a-elimination over the /3-elimination of III-

12 is attributed to the steric repulsion between the bulky groups on the /S-carbon and ligands on the titanium center, which prevents 111-12 from reaching the transition state for the (3- elimination effectively. The yields are moderate regardless of the nature of halides, although iodides are commonly utilized. Cp2TiCl2

P(0Et)3 Mg, 4Â molecular sieves

Cp2Ti[P(OEt)3l2 R2.R3 CP2R3R2 R2R3 III-6 ^2 disproportionation V ^ V Cp2TiX2 ^1^>^^1 111-11 111-12 a-ellmlnation R, R3 Ri CH3 O R2 R3 |R5 - Cp2Ti=0 ^P^TpO R4^YRA. 5 R2 R3 -YR. , X^TiCp2 R4 R2 R,

Ri. R2. R5= alkyl. R3=H or alkyI, R4=alkyl or aryl, Y=C, O

Scheme 3.9 Takeda alkylidenation using alkyl halide-Cp2Ti[P(OEt)3]2 system

3.2 Design Strategy

In Chapter Two, both the original and the revised syntheses of sensitizer-drug

complexes involve two tandem reactions on the same alkynyl carbons of the ethoxyacetylene.

In the latter case, the ineffectiveness of the first reaction's product towards the second reaction

accounts for the failure of complex synthesis. We envisioned that such a dilemma could be circumvented by breaking the inherent chemistry connection between the drug attachment step and the sensitizer attachment step; that is, we can design a linker molecule, in which two functionalities A and B are separated by a spacer C, to facilitate the complex synthesis

(Figure 3.2).

spacer C

Figure 3.2 Diagram of the proposed linker molecule Functional group A is responsible for the drug attachment and a photocleavable linkage will be created after the attachment. Functional group B is dedicated to the attachment of the photosensitizer. Due to the unique reactivities of porphyrinoid compounds, it is preferable that the drug attachment occurs ahead of the photosensitizer attachment. Therefore, mild reaction conditions are required for the sensitizer attachment at B to preserve the labile linkage at A. The spacer C serves as the backbone of the linker molecule to host functional groups A and B. Its structure can vary from a simple carbon-chain to a complex structure, e.g. a steroid, which might offer additional benefit such as site-targeting (section 1.3). Obviously, the current design provides maximum flexibility for sensitizer-drug complex synthesis.

The general diagram of the drug incorporation and the drug release is depicted in

Scheme 3.10. After the attachment to the A terminus, the drug becomes a prodrug moiety, which will reacquire its bioactivity during the drug release stage when illuminated. As discussed in section 1.4, electron-rich olefins, such as enol ethers, are chosen as the photocleavable linkage for our project. Titanium-carbene based alkylidenation of carboxylic acid derivatives presents itself naturally as the drug attaching reaction at terminus A.

Regarding the appropriate sensitizer attaching reactions, Steglich-type esterifications

(carbodiimide-based couplers are used)'^' or Pd-catalyzed cross-coupling reactions"^' should be mild enough for the task. In addition, the flexibility of the current design allows the sophisticated photosensitizers,'^^' '^'* such as those bearing target-specific components or amphiphilicity modulating components, to be utilized to prepare potentially more robust sensitizer-drug complexes, providing the corresponding sensitizer-acid or sensitizer-halide substrates are readily available. (linker)

Drug Attachment Step

prodrug

Î targeting • icomponentr'

,' other ' Sensitizer Attachment Step 'component(s),' lyPhotosensitizeiy Drug Incorporation Stage

,'amphiphilicity\ ' modulating < \ component /

I targeting ' ^component/ visible ' lights,

other jComponent(s>

^' ^^ (sensitizer-drug complex) 'amphiphilicity' 1^ modulating ' V component '

[ targeting i O2 hv Drug icomponent/ Release Stage

other \component(s). ' \^otosensitizei^ +

, amphiphilidtyi \ modulating ,' \ component /

Scheme 3.10 General diagram of the sensitizer-drug complex synthesis and the drug release

(The solid-lined components are required and the dash-lined components are optional) At the time we started this project, Takai alkyUdenation had been extensively tested as a general methodology while Takeda alkylidenation was an emerging process. Based on the

Takai alkylidenation, synthesis of the sensitizer-drug complexes using the linker molecule was proposed (Scheme 3.11). A 1,1-dibromo carbon unit is required as the functional group A for the Takai alkylidenation, which can be prepared by the alkylation of the dibromomethane carbanion. Therefore, starting from the commercially available 3-chloropropanol, the linker molecule 111-15 can be prepared by a simple three-step process involving silyl protection,

Finkelstein halogen exchange and alkylation. The silyl protection of the hydroxyl group is based on the fact that 1) the hydroxyl has to be masked due to its interference with alkylation and the Takai reaction; and 2) the triisopropylsilyl protection group is stable against LDA and

TiCLt and can be easily removed by fluoride, without damaging the heteroatom-substituted olefin linkage. After 111-15 is prepared, the alkylidenation of drugs with it, followed by the deprotection and Steglich esterification, will generate the desired photosensitizer-drug complexes.

TIPSCL V Nal ^ CHoBro ,' HO' CI —z—r >~s\o imidazole, DMF - \ 111.13 IIM4 111-15

linker

R'"X. YR ,Br drug , ^ ^ - TBAF TIPSO • TIPSO ^ ^ YRJ Br TiCU, TMEDA, n 11-15 Zn, THF-DCM ' "prodrug moiety" coupler sensitizer hCOOH

Y= O, S, N

Scheme 3.11 Proposed synthesis of the linker molecule and sensitizer-drug complexes 3.3 Synthesis and Structure Characterizations

The silyl protection of 3-chloropropanol followed Corey's protocol'^^ using imidazole and TIPSCl in DMF and 111-13 was generated in quantitative yield. Refluxing of an

acetone solution of 111-13 and Nal (3 eq.) for three days gave 111-14 quantitatively. The

Finkelstein reaction is an equilibrium process driven by the large solubility difference of metal salts in organic solvents. In our case, Nal is completely soluble in acetone while NaCl precipitates out. In the following alkylation reaction, a THF solution of CH2Br2 was first added dropwise to a THF solution of LDA at -90°C (hexane/liquid N2-bath) for deprotonation, followed by the dropwise addition of a THF solution of 111-14. The reaction mixture was stirred at -90°C for two hours before the temperature was slowly elevated to -30°C and maintained for another two hours. Acid quenching of the crude mixture followed by vacuum distillation gave 111-15 in 50 % yield. Cautious temperature control is crucially important to assure good yields.

As a test of principle, only simple esters and amides, rather than real drug molecules, were employed to build final complexes with 111-15. Ethyl butyrate, ethyl benzoate, methyl pivalate and 1 -benzoylpiperidine were utilized, representing aromatic esters, aliphatic esters, sterically-demanding esters, and amides. As discussed in section 3.1.2, Takai alkylidenation of carboxylic acid derivatives involves the in situ generation of the active titanium species, followed by the treatment with carbonyl substrates. Interestingly, the progress of the whole procedure can be monitored by a series of color-changing phenomena. A DCM solution of

TiCU was first added to a round bottom flask with THF at 0°C and the resulting yellow solution became brownish yellow after the addition of TMEDA. The subsequent addition of zinc dust and a trace amount of PdCb with a gradual increase of temperature to 25°C turned the color of the mixture to greenish blue, which indicated the formation of active titanium species. After an additional one-hour stirring, a THF solution of a dibromoalkane and carbonyl compound mixture was added dropwise and the reaction system slowly changed from blue to reddish brown over 4 to 12 hours, indicating the completion of the alkylidenation.

The optimized mole ratio of the reagents had been determined as 1:2.2:4:8:9:0.045 for carbonyl substrates:CH2Br2:TiCl4:TMEDA:Zn:PdCl2.'^^ It is vital to the success of alkylidenation to pre-activate the zinc and to use a freshly prepared DCM solution of TiCU rather than the commercially available one.'^^ Generally, the alkylidenation products are susceptible to acid-catalyzed hydrolysis and the weakly acidic silica gel should be avoided during product purification. In our experiments, deactivated basic alumina (III) was used in all the chromatography.

The results of the Takai alkylidenation and the subsequent desilylation are summarized in Table 3.1. All the ester substrates were converted to enol ethers in good yields with high Z-selectivity (entries 1 to 3). The stereochemistry of the enol ethers was determined by selective NOE experiments on the Takai alkylidenation products or the final complexes.

The selective NOE experiment of III-17 is shown in Figure 3.3. When the olefinic proton at

5.32 ppm was irradiated, NOE was observed on the ortho-proton of the phenyl group at 7.43 ppm and vice versa, which ascertains the Z-configuration of III-17. The Z-selectivity can be ascribed to the lower steric repulsions between the olefin substituents of the Z-isomer compared to those of the E-isomer. Indeed, a complete Z-selectivity was observed in the alkylidenation of methyl pivalate (entry 3). It is notable that the success of entry 3 is in direct contrast to the allegation "Pivalate esters are poor substrates for Takai alkylidenation,...".'^^

Unfortunately, the product of the amide alkylidenation (entry 4) was too unstable to survive the work-up procedure and only hydrolysis product was collected.

Table 3.1 Takai alkylidenation of carbonyl substrates and the desilylation

TiCl4, TMEDA, -Br Zn, PdCl2 TIPSO' Br Ri YR2 THF-DCM, r.t TIPSO

Entry RI R2 Y Alkylidenation i Yield [ Z/E* T Desilylation 1 Yield Product Product I (%) 1 n-Propyl Ethyl O 111-16 88 I 91:9" 111-19 n/a IT 2 Phenyl ; Ethyl O 111-17 94 ; 93:7 Tll^Q 98 3 1 t-Butyl ! Methyl O 111-18 771T00:0'^ ; lil^" 66 n/a (TO n/a n/a n/a n/a byy selective NOE of the final complexes, -^product was directly subjected to next step reaction.

*i>W>ii»i»|i|iDtyH>iW4n^l|l#iiiwi

i sityl

7.0 6.0 5.0 ppm (f1) 4.0 3.0 2.0 1.C

Figure 3.3 Selective NOE spectra of 111-17 (CDCI3, 400 MHz, upon irradiation at 7.43 ppm

and 5.32 ppm) The removal of the triisopropylsilyl protection group was completed within minutes

after treatment with tetrabutylammonium fluoride in the presence of 4Â molecular sieves.

A flash filtration of the crude mixture through a short basic alumina (activity (III)) column

was enough to furnish the pure alcohol products. 111-20 and 111-21 from the deprotection of III-

17-Z and 111-18 were stable enough for structural characterization, while 111-19 was unstable

and had to be used immediately for the next step (Table 3.1).

Two different porphyrinoid-based photosensitizers 111-22 and 111-23 were used in the

synthesis of final complexes (Figure 3.4). 111-23 is a racemic mixture and only one enantiomer is shown here. As a side-product during the manufacture of Visudyne®, it was obtained from QLT Inc.. 111-22 was synthesized in 12% overall yield via a two-stage process:

1) condensation of pyrrole, benzaldehyde and 4-carboxymethylbenzaldehyde to generate III-

24 (BF3-Et20 catalyst, Lindsey's protocol); and 2) base-catalyzed hydrolysis of 111-24 to furnish llf-22 (Scheme 3.12). 188, 189

OH

111-22 111-23

Figure 3.4 Photosensitizers used in the synthesis of complexes 111-22

111-24

Scheme 3.12 Synthesis of 111-22

A series of sensitizer-"drug" complexes 111-25 to 111-28 were generated by the

Steglich esterification of porphyrinoid acids with different esterifying alcohols in moderate to good yield (Table 3.2). The coupling agents l-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N,N'-diisopropylcarbodiimide (DIC) showed similar results. To avoid hydrolysis, the crude reaction mixture was concentrated and directly chromatographed on basic alumina (activity (III)) without work-up. Table 3.2 Esterification of porphyrinoid acids

Entry ! Porphyrinoid acid Alcohol Coupler Product j Yield (%)

1 111-22 111-19 EDC i^ 111-25 T'70^ 2 111-22 111-20 DIC ' ill-26 i 81

3 111-22 111-21 EDC 1 111-27 'Î 72" " 4 111-23 111-20 DIC : fll-28 " Isolated yield.

As shown in Scheme 3.13, the mechanism of Steglich esterification starts with nucleophilic attack of the carboxylate on the central diimide carbon. The resulting O- acylisourea 111-29 is attacked by DMAP and releases urea and an acylpyridinium species III-

30, which is then reacted with an alcohol to give the final ester product.'''^ DMAP is a highly active acyl transfer agent and is of pivotal importance to this esterification.'^' In an esterification reaction of 111-22 using DIC coupler without DMAP, significant amounts of N- acylurea 111-31 were isolated, which is believed to be a rearrangement product of III-29-TPP

(Scheme 3.14).The structure of 111-31 was characterized by X-ray crystallography (Figure

3.5).The phenyl rings at C-10 and C-20 are disordered over two orientations, only one orientation of each is shown. H-OR

O 0-H Por—^ Ri-N=-- N f Por OR 1. O ^ HN k:û?\Por ^ * Por OR Ri - DMAP 111-29 111-30 H H

Scheme 3.13 Mechanism of Steghch esterification

PP

N 0

HN 0^0 HN HN-^O

1-29-TPP l„.31

Scheme 3.14 Rearrangement of III-29-TPP

C24 C23

C54a

C53a

C37 ^C36

Figure 3.5 An ORTEP drawing of 111-31 showing thermal ellipsoids at 50% probability level.

H atoms have been omitted for clarity Final complexes 111-25 to 111-28 were structurally characterized by 'H and '''C['H]

NMR spectroscopy, UV-Vis spectroscopy, and MS spectrometry. The 'H NMR spectra of

TPP-based porphyrin products 111-25 to 111-27 are straightforward, with porphyrin backbone proton signals concentrating at the downfield region without interfering with the proton signals from the esterifying alcohol chains. The Z-configurations of 111-25 and 111-27 were confirmed by selective NOE experiments with the correlation signals between the A'* and A*' protons in 111-25 (Figure 3.6) and between A"* and A'' protons in 111-27 (Figure 3.7).

5.0 O.C ppm(f1)

Figure 3.6 Selective NOE spectra of 111-25 (do-acetone, 400 MHz, upon irradiation at 4.62

ppm and 2.09 ppm) 111-27

mm» X. ...i,,

mm sol H20

A3 ^2

5.0 o.c

Figure 3.7 Selective NOE spectra of 111-27 (C6D6,400 MHz, upon irradiation at 4.77 ppm

and 1.16 ppm)

'h, "C['H], and APT NMR spectra of 111-26 with detailed peak labelings are shown in Figure 3.8. With the aid of HMQC and HMBC spectra (Figure 3.9 and 3.10), all the carbon signals were unambiguously assigned. Resonances of the a- and /3-carbons are not seen in the spectrum. This is a common phenomenon for TPP derivatives, due to severe peak- broadening by the NH-tautomerization effect.'^' However, the correlation signal from 0- protons in HMQC suggests that the /3-carbons should appear around 132 ppm. The quaternary meso-caxhons appear as sharp peaks at 121.5 ppm (C-15), 121.3 ppm (C-10, C-20) and 119.7 ppm (C-5), determined by the ^JC-H correlation signals from the or/Zzo-protons of phenyl

substituents in HMBC. The chemical shifts for the me^o-substituent phenyl carbons decrease in the order from lower field to higher field as: carbons attached to porphyrin (C-T) > ortho- carbons > /»ara-carbons > meta-carhons, in the same pattern as reported by Abraham et al.}^^

In particular, all carbons from the C-5 phenyl substituent resonate at a relatively lower field compared to other /?2e5o-substituent phenyl carbons, due to the negative mesomeric effect of thepara-carbonyl group. Olefinic carbons A'* and A^ appear at 114.4 ppm and 155.3 ppm, due to the positive mesomeric effect of the ethoxy group on the /3-carbon and the negative inductive effect of the ethoxy group on the a-carbon. The complete '^C['H] resonance peaks of 111-26 are listed in Table 3.3, which is a handy reference for spectral interpretation of other lll-22-based structural analogues, hideed, the '^C['H] spectra of 111-25 and 111-27 are highly similar to the "C['H] spectrum of 111-26 and their spectroscopic data are presented in Chapter

Five. para 20"

orthoK^2(i^ 20^

ppm (11) ortho meta ort/jo, meta, or para refers to relevant prêtons of the phenyl groups at 10,15,20 positiorB ^10 H2O sol I if A" LJii NH 7^ 5.0 ppm {t1 ) O.C

Figure 3.8 'h, and APT spectra of 111-26 (do-acetone, 400 MHz/100 MHz) J \ ,1/ ^ L

h5C

©

h 10C

ppm (t1

8.0 7.0 6.0 5.0 4.0 3.0 2.C ppm (t2)

Figure 3.9 HMQC spectram of 111-26 (de-acetone, 400 MHz) Figure 3.10 HMBC spectram of 111-26 (dé-acetone, 400 MHz) Table 3.3 '^C['H] NMR spectral data of 111-26 (do-acetone, 100 MHz)

111-26 Category Label Ô (ppm) Category 6 (ppm) a-Carbons : l,4,6,9,n,14,16:i9 Carbons of 65^6^ /3-Carbons : 2,3,7,8,12,13J7,l8 ^^"-132; "" r"^ ^ ' 29T8 esterifying meso- ' 5 ' 1T9 J ' Carbons 10,20 niX alcohol chain ""'""x^""""i " 1144 '15' ' ' ^"^1553 Phenyl carbons r5'""" 147.5 ' '^137.4" (C-D r "Topis', 20'^ 142.8 ^ Y26.T Phenyl carbons :"""'"^ '^"5""" 135.4 129.3 {ortho) 1353 [^^'"^^ T28.7

Phenyl carbons ] ^ ? " ; 128.9^ 66.7 {meta) r 10^, 15^2:0^ Î ^ I27.8 r^A""^- 15^8 Phenyl carbons 131.0 (para) 1 127^8^ i 1 Carbonyl 166^ ;

The 'H and '^C['H] spectra of 111-28 are complicated due to the low syinmetry and large number of substituents around the macrocycle. With the collaboration of COSY, APT,

HMQC and HMBC NMR techniques, they are completely assigned as shown in Figure 3.11.

All 54 carbons of 111-28 show up as sharp peaks in the '^C['H] spectrum, including a-carbons and /3-carbons, in contrast to its TPP counterpart. The unambiguous peak assignments of 'H and '^C['H] spectra consist of three stages: 1) Most of the proton signals were assigned with the aid of COSY (Figure 3.12). Two complex multiplets at ca. 4.44 ppm were assigned to the diastereotopic protons of methylene A', due to the proximity to chiral carbon 7*. Similarly, methylenes 13' and 17' can be distinguished by the multipHcity; i.e., 13' protons appear as multiplets while 17' protons show a triplet. However, four meso protons in the downfield region, three methoxy groups and three methyl groups of 2', 12', and 18' await further discrimination; 2) Most of protonated carbons can be assigned by HMQC (Figure 3.13). Due to the diverse local environments, quaternary carbonyl carbons C-l\ C-7^, C-13\ and C-17^ can be readily assigned by the HMBC correlations (Figure 3.14) with protons two or three bonds away. The establishments of these resonances in turn helped the 'H and '^C['H] assignments of the adjacent methoxy groups at 7^, 13"* and 17"* by HMBC and HMQC; 3) For quaternary a-carbons and )3-carbons, ring A and ring B are good to start with because of then- distinctive substituents at /3-positions. Thus, carbon signals at 6, 7, 8 and 9 (ring B) were assigned by the correlations with the protons of 7^, 7^, and 7"* in HMBC spectrum. The estabhshments of C-7 and C-8 helped determine the me^o-proton resonances at 5 and 10. For ring A, HMBC signals from proton 3' and 5 determined the carbon signals at 2, 3 and 4, which in turn helped assign the meso-proton at 20 and the methyl proton of 2* by HMBC.

Consequently, the remaining me^o-proton signal of 9.87 ppm should be assigned to H-15, which, together with protons of 13' and 13^ or 17' and 17^, can help determine the a- and /3- carbons of ring C and D, as well as the remaining peripheral methyl groups at 12 and 18. The complete 'H and '-^C['H] chemical shifts of 111-28 are listed in Table 3.4 and Table 3.5 as references for the spectrum interpretation of IU-23-based structural analogues. To our knowledge, this represents the first '^C NMR characterization of benzoporphyrins. 17" 13*

18^ 76 12^ A' 13' 17' AlO

1 li j |! 20 15 05 A« 71 1 ,1 I ,2b A" \f A. , i m1 J] LL ' UL f

5.0 ppm(tl) o.c

A8 13* 17 18 11 isjr 14192 12 3

»0«

A^A' A2 A9 133 12 ^^13^ A3 i 21 32 20, A' j 7 78/ 72 15 510 7= î^pa impur

MM

! 1 1 i . . , i . "1 |1

1

150 100 ppm (t1) 5C Figure 3.11 H, C[ H], and APT spectra of 111-28 (d^-acetone, 400 MHz/100 MHz for 'H/ '^C) 0

— 2.0

0 3 .0 -3.0

0 -4.0

I -5.0

-6.0

-7.0

I h 8.0

'ppm (t1 ^ I ! I I I r I I I I I I I I I I I Ï i I I I 1 i 1 I I—1—I—i—r 8.0 7.0 6.0 5.0 4.0 3 0 2 0 ppm (t2)

Figure 3.12 COSY spectram of 111-28 (de-acetone, 400 MHz) J , * iiUl

r- 50

h 100

ppm (t1

I i M I I [ I I I [ 1 ! I I 90 8.0 7.0 6.0 5.0 4.0 3 0 2 0 ppm (t2)

Figure 3.13 HMQC spectrum of 111-28 (da-acetone, 400 MHz) K 50

K 100

h 150

ppm (ti

i I I I r 1 i 1 I I 'I I I I I T 1 I I ! I M 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2 0 1 0 ppm (t2)

Figure 3.14 HMBC spectmm of 111-28 (de-acetone, 400 MHz) Table 3.4 'H NMR spectral data of 111-28 (dô-acetone, 400 MHz)

111-28 Category Label b (ppm) Category Label l (ppm) (multiplicity) (multiplicity) me^o-Protons i 938 (s) Peripheral ?" ; 3.66 (s) 10 r""9:57(s) Protons ^ 3' ; 8.28 (dd) 15" r 9.86 (s) \ ^ 6:45 (d)' 20 ^9^89 (s) "3^" "l " 6!l5 (d) -NHs -2.22 (s) " " •'"7'"" ' " "5:17 (s)" Protons of A' T42(m) ""7^ 7.83(d) A^ 1 2.00 (m) " r ' 7;6:gi (d) Esterifying A^ 1 2.54 (q)' 1 1^83 (s) Alcohol Chain "A^"" 1 5.51 (ty T"""^i:i5(sy ! 7.54(d)" ! 3.48 (s) A^^A^^ 7.38'"(m) """"13^""' ' 4.28 (m) A^" 7^27 (m) ^T3^ '"^X22'(t) A'' " ; 3.76 (q) T1.58 (s)" A"" " ; 1.33 (t) "17^ " i 4.15(t) "17^^"" H' "^^3.17 (t) Table 3.5 '^C['H] NMR spectral data of 111-28 (dô-acetone, 100 MHz)

111-28 Category Label l (ppm) i Category i Label h (ppm) a-Carbons ' 1 ' 152 J r /3-Carbons 1"2"""'" T"""'" 13Ï3""' '4 " i 137.5 ! '3^ ' '" \3\?1 6 '"166.7" i i7 i'53^4 1 9 : 153^9 i 8 """" [ 156^6 " 11 : 12 \ " 132!4

14 i " 135S) ' 1 : Ï3" "" 137.7 " 16 :T52.5"" \ \A\A ' 19 ;"134.6 ( ' ""18 ' ;'""^li^J me^o-Carbons :'94^r Peripheral • ' Y r"12^5"""""^ To i"92 j6'"\ Carbons : ^ 3^ ' 1""^"""i3o;4

^15' !^99X'1 i ^3^"~ r ' 20 : '100^' " 1"7'"" \ 48.6 Carbonyl "'f'" " i7i;o . ^••"""•""""7^"" ! "" T23.8 Carbons ^7«" ;^"T67.4' i 7' 1" 137^2 "13^ :'173^5 r7'"' ; 1144 ' 17^ '173^8" "" ; i " """7^ '"" 1 '28.0'" Carbons of ""a'"'^""" r"^ 1 "5"L5" Esterifying '"'"A^"^""""""; 29.8 ;^^ 11.0 Alcohol Chain ^"A^^ \"23 A" !^ 13' """"""'"" r-^j^"- A* 114^4 ^ ' w" i ^^36:9" 'A^"' : Ï55ÏÏ ; ^""""'""13^""""'" A^ ""137^3 1 ^"""" If ' i 22.2 A^^V'' 126.7 1 ; ' w ^ " A«^A«'' ^ " l"29.2" ] \ ""• 17^ """""" !51:7' 128^6^ 66.6 " A^^ 15^8 \

The UV-Vis spectra of 111-25 to 111-28 in CH2CI2 are shown in Figure 3.15. Three

TPP-based complexes exhibit nearly identical spectra with a strong Soret band at 418 nm and

Q-bands at 514 nm, 550 nm, 591 nm and 651 nm. For 111-28, a characteristic long-wavelength absorption band is shown at 690 nm. —111-25 — 111-28 111-27 111-26

800 Wavelength (nm)

Figure 3.15 UV-Vis spectra of 111-25 to 111-28 in CH2CI2

3.4 Photooxygenation of Photosensitizer-"Drug" Complexes

3.4.1 Experimental Design

The Ught source for the photoirradiation was an Oriel lamp house with a 250 Watt arc lamp. The optical range of the irradiation was controlled by different filters. For TPP-based complexes, an aqueous K2Cr207 solution served as a light filter to provide an irradiation range from 540nm and up. For benzoporphyrin-based complexes, a Corion filter with a transmittance range between 600nm to 700 nm was used. In either case, the irradiation was carried out in the visible light range. The photooxygenation took place in an NMR tube with a sensitizer-"drug" complex dissolved in deuterated solvent (1 x 10'^ to 1.5 x 10"" M). The NMR tube was placed in the light path 10 cm from the lamp, where the light was focused by the adjustable lens of the lamp house. The temperature of the solution was maintained at room temperature by water-bath. In one specific case {vide infra), an acetone/dry ice-bath was used for a -78 °C photoirradiation reaction. During the photooxygenation, the NMR tube was open to air to allow the slow diffusion of oxygen into the reaction solution. It was found unnecessary to introduce an additional source of oxygen due to the small reaction scale.

The progress of the photooxygenation was monitored by NMR and GC.

Approximately equimolar amount of 1,3,5-trimethoxybenzene was added to the system as internal standard prior to the photoirradiation. Blank tests showed that 1,3,5- trimethoxybenzene does not react with singlet oxygen and remains intact under the photooxygenation conditions. At the GC injection temperature (220 "C), the dioxetane product from the photooxygenation should instantly decompose to give carbonyl fragments.

Therefore, GC quantification of the drug molecule (esters in this chapter) from the crude photooxygenation sample should provide a direct indication of the total amount of releasable drug molecules by photoirradiation.

The conversions of starting materials and the yields of photooxygenation products were determined by NMR integration of corresponding characteristic peaks referenced to that of the internal standard. Yields of the released drugs were also calculated by GC using internal standardization. Since every compound responds differently to the GC detector, the relative response factors (F) of different drugs relative to the internal standard were calculated by the following procedure: 1) a series of standard solutions of the targeted compound and

1,3,5-trimethoxybenzene mixed at different molar ratios were prepared. The concentration of the standard solutions are close to that of the substrate in photooxygenation; 2) GC spectrum of each solution was acquired three times in a row and the average peak area ratio of the targeted compound over the internal standard was determined; 3) The relative response factor

(F) was calculated with Equation 3.1 by linear regression.Consequently, the yield of the targeted compound (drug) released by photooxygenation were readily calculated using

Equation 3.2. Due to the small reaction scale, the molar ratio of starting material over the internal standard in Equation 3.2 was determined by NMR integration rather than by direct weighing. As a result, the yield calculated by GC incurs the superimposed errors from both the GC and the NMR instruments. Therefore, the yield determined by NMR is generally favored over that by GC, except in some cases where the severe overlap of peaks of the photooxygenation products prevents proper NMR integration.

Aanalyte _ Mgnalyte /. ao -c ^MR - - ^analyteX .. 1-6. «f^analyte/int.std.- "^analyte X iVlrCanalyte/int.std. Equation 3.1 "int.std. int.std. y j

"^^aMe ^analyte 1 / _1_ > Yield- "^anaMe, ^^,3,^. ^ A,^.3t,. Fan^yte /. ^'^ana^e/inl.std.X p^^^^ \ Equation 3.2 Ms.m. r ' MRs.m./intstd. / Mint.std. Mmt.sy ^ '

A; GC peak integration area, F: relative response factor, M: mole, AR: area ratio, MR: molar ratio

In addition, Mass Spectrometry is also employed to analyze the photooxygenation crude mixture and to confirm the existence of proposed products or intermediates.

3.4.2 Results and Discussion

3.4.2.1 Photooxygenation of TPP-Ethyl Butyrate Complex 111-25

The photooxygenation of 111-25 was carried out under three different conditions: in

CDCI3 at room temperature, in do-acetone at room temperature and in CD2CI2 at -78°C. The results are summarized in Table 3.6. Table 3.6 Photooxygenation of 111-25

Entry""' 1 Solvent ! Conc i Temp Time Conv 111-32 i 111-33 ^, 111-34 1 Total ^ [2+2] 1 Ester (%) ! (mM) i (°C) (min) (%)" (%)^ ; {%Y 1 or Ester (%)' ; [2+2] (%)^ :"ene" \ (by GC)^ 33-" i CDCI3 >95 42 \ 39 i 8' !47 ' 53:47 '1 dg-acetone 1 12 i "25^" 90 '""42 [ ""10 " \ 12 i """22 34:66 f 19 _^ : cD2ci2^ T 14" " 1 ''-78' ' 240" ^>95 33" i n/a i 60 ^ i ' '60 65:35 ! 53" ' " For ail three experiments, molar ratios of the substrate (based on A** of 111-25) to the internal standard (based on IS^), conversions and yields (based on 100% conversion) were determined by 'H NMR spectroscopy. * Based on A' of 111-25. ' Based on B" of 111-32. Based on of 111-33. " Based on D" of 111-34 or E" of ethyl butyrate. ^ Sum of the decomposed and the remained dioxetane. ^ Determined by GC peak area ratios and calculated using Equation 3.2, F= 0.78. The 50 minutes irradiation of 111-25 in CDCI3 gave the desired [2+2] cycloaddition

products in 47% combined yield, together with the "ene" product 111-32 in 42% yield (entry 1).

About 36% of dioxetane 111-33 decomposed during the photoirradiation to give a TPP-

aldehyde 111-34 and ethyl butyrate ("drug"). Attempts to isolate hydroperoxide 111-32 and

dioxetane 111-33 by chromatography were unsuccessful. 111-32 readily decomposed to give

complex side-products on either silica or alumina columns, and 111-33 partially decomposed to

give 111-34 and the ester. 111-34 was isolated and its NMR spectroscopic data is an important

reference for the interpretation of the photooxygenation. A detailed NMR analysis of the

photooxygenation process is discussed later in this section.

The photoirradiation of 111-25 in de-acetone for 30 minutes generated hydroperoxide

111-32 in 42% yield and [2+2] cycloaddition products in only 22% combined yield (entry 2).

The chemoselectivity of [2+2] over "ene" reaction is down from 53:47 in entry 1 to 34:66 in

this reaction, which is not the normal result considering that d^-acetone is more polar than

CDCI3 and should presumably favor the [2+2] cycloaddition reaction. In Gollnick's study of

singlet oxygenation of rigid cyclic enol ethers, polar solvents such as acetone, chloroform and

dichloromethane gave the [2+2] cycloaddition products in similar yields.'"

111-25 was also subjected to low temperature photoirradiation in CD2CI2 (-78''C)

(entry 3). It took 4 hours to finish and the [2+2] cycloaddition products and the "ene" product

were generated in 60% and 33% yields respectively. This result confirms that the [2+2] cycloaddition reaction predominates in the low-temperature singlet oxygenation reaction.'**^' '^^ It is noteworthy that dioxetane rapidly decomposed during this low-temperature

photooxygenation. Even when only 41% of 111-25 was converted (1 hour 30 mins after the

start of the photoirradiation), none of the dioxetane can be found and the ester and

hydroperoxide are generated in 26% and 13% yields respectively. It is evident that visible

light, instead of heat, has facilitated the decomposition of dioxetane in this case.

In all three photooxygenations, a completely regioselective "ene" reaction was

observed; that is, only the allylic hydrogen of the |8-alkyl chain was abstracted while that of

the geminal alkyl group was intact. Such selectivity can be explained by the combination of

the cis-directing effect and the anomeric effect, which will be discussed in section 4.4.2.

Furthermore, the "ene" reaction is also stereoselective. Only the E-isomer of the

hydroperoxide product was observed with a coupling constant of 16 Hz. The crude reaction

mixtures from all three photooxygenations were subjected to ESI-MS analysis and ion peaks

of 729 m/e and 845 m/e were observed, referring to the protonated 111-34 and the

hydroperoxide or the dioxetane.

Step-by-step NMR spectra of the photoirradiation of 111-25 in CDCI3 were shown in

Figure 3.16. The gradual consumption of 111-25 is obvious as the olefinic proton signal of A"*

(4.65ppm) and the adjacent methylene signal of A^ (2.37ppm) decay continuously. This is

accompanied by the gradual increase of peaks from the hydroperoxide, the dioxetane, and other photooxygenation products. As expected, the porphyrin backbone proton signals change only minimally during the photoirradiation, as the singlet oxygenation took place exclusively on the enol ether of the esterifying alcohol chain, which is far from the porphyrin core. The 'H

NMR spectrum of the crude photooxygenation mixture was interpreted by combining the information from COSY (Figure 3.17), authentic sample comparison (the ester and 111-34) and quantification analysis using NMR integration.

IS2 183 I 3 B^C* -OOH D* i f i I C9

XHL.fJ SOmins

JlJI Lxk L>À^i^J 30 mins

% UM: 20 mins

/_M^yy-s>w^- \J K_ 10 mins

IAA. 0 min

9.0 8.0 7.0 6.0 5.0 4,0 3.0 2.C 1.0 ppm (t1)

Figure 3.16 'H NMR spectral sequence of the photooxygenation of 111-25 (CDCI3, 400 MHz,

proton labelings please refer to those in Table 3.6) .,L 3._._,»».jJ'WA„ A^^A'W--*^ '"^Jw

2.0

I) l! i

" 3.0

4.0

5,0

o ©

6.0 ; ppm (ti

6.0 5.0 4.0 3.0 2.0 1.0 ppm {t2)

Figure 3.17 COSY spectram of the photooxygenation crade mixture of 111-25 (CDCI3, 400

MHz, 50 min irradiation)

The 'H-'h COSY NMR technique is especially helpful in distinguishing various photooxygenation products since their structures only differ in the area close to the original double bond of the esterifying carbon chain. As the COSY correlation signals reveal the direct connectivity of the protonated carbons adjacent to each other, it is easy to trace the esterifying chain one carbon after another. Furthermore, photooxygenation products were generated in different yields and correspond to different integration areas in the NMR spectrum. It is therefore convenient to group the structural fragments derived from COSY analysis when the carbon chains are disrupted by quaternary carbons. The most prominent peaks newly

emerging along the photooxygenation are the triplet-triplet at 6.02 ppm and the doublet at

5.63 ppm. They are correlated in the COSY spectrum and were thus assigned to the olefinic

protons at and B"* of the hydroperoxide 111-32. Consequently, B^ and B' were determined

by COSY. Another prominent new peak is the triplet at 5.43 ppm, which was assigned to the

methine proton (C"*) of the four-membered dioxetane ring in 111-33, and protons of C' to C^

were subsequently determined by COSY. The proton signals from the B^ to B^ chain or C*' to

C^ chain were determined by COSY and distinguished by their integration differences as III-

32 was generated in slightly higher jàeld than 111-33, and so were the protons resonances at B^

to B"^ and C^ to C'°. In both 111-32 and 111-33, diastereotopic methylene protons adjacent to

the newly formed stereocenter appear as complex multiplets, such as protons of B^ at 3.68-

3.53 ppm and C^ at 3.81-3.63 ppm. In the downfield region, the newly emerged singlet at 7.57

ppm with the integration equivalent to IH of the hydroperoxide was attributed to -OOH (the

-OOH signal appears at 10.10 ppm in de-acetone, entry 2). Such assignment corresponds well

to the reported signal of 7.66 ppm in CDCI3 for the -OOH of an acychc a-alkoxy hydroperoxide.'" In addition, the singlet at 9.93 ppm, the quartet at 4.12 ppm and the triplet at

2.77 ppm were assigned to D"*, and respectively by comparisons with the NMR spectra of the authentic 111-34 and ethyl butyrate.

The crude reaction mixture of entry 1 was also characterized by '^C['H] NMR and

APT (Figure 3.18), HMQC (Figure 3.19) and HMBC (Figure 3.20) NMR spectroscopy. Only the major components of the crude mixture, namely 111-32, 111-33 and the internal standard, were detected in the '^C['H] spectrum. Carbon resonances from the tetraphenylporphyrin macrocycle remain essentially unchanged for 111-32 and 111-33. With the complete assignments of the proton resonances, signals from the protonated carbons and quaternary carbons in the esterifying alcohol chains of 111-32 and 111-33 can be readily determined by HMQC and HMBC. For 111-33, the methine carbon (C"*) and the quaternary carbon (C^) of the dioxetane ring appear at 89.3 ppm and 110.1 ppm respectively. For 111-32, peaks at 130.9 ppm and 130.2 ppm are assigned to the olefinic carbons of B"* and B^, while the quaternary carbon of B^ appears at 106.9 ppm. The 'H-'^C correlations in HMBC leading to the assignments of these characteristic carbon resonances are illustrated in Figure 3.20.

IS2 IS3 i

B- IS'

B'» C^BS I ii

CH

' " 1 C CH2

ppm (II) Figure 3.18 '^C['H] NMR and APT spectra of the photooxygenation crude mixture of 111-25

(CDCI3, 100 MHz, 50 min irradiation) OOP

e

h-5C

10C

' 0

h ppm (ti y i I I I ] i I I i~[ I ! I I j I I I I I I I y 1 I I I I I I I I I I I I T"! i I I i 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 ppm (t2)

Figure 3.19 HMQC spectmm of the photooxygenation crade mixture of 111-25 (CDCI3, 400

MHz, 50 min irradiation) 84 82

I C6 i

- 90

10C

B5-

C5- - 11C

12C

83- — 13C 84"

ppm (ti

6.0 5.0 4.0 3.C 2.0 ppm (t2)

Figure 3.20 HMBC spectrum of the photooxygenation crude mixture of 111-25 (CDCI3, 400

MHz, 50 min irradiation)

The photooxygenation of 111-25 in d<5-acetone at room temperature (entry 2) and in

CD2CI2 at -78°C (entry 3) were studied by the same approach except that the crude reaction mixtures were only characterized by 'H NMR and COSY. The spectral sequence and the COSY spectrum of the entry 2 reaction are presented in Figure 3.21 and Figure 3.22, while

those of entry 3 reaction are presented in Figure 3.23 and Figure 3.24 at the end of this

chapter.

3.4.2.2 Photooxygenation of TPP-Ethyl Benzoate Complex 111-26

Photooxygenation of 111-26 (4 mM) was carried out in C^Dé at room temperature.

After 22 minutes irradiation, 95% of 111-26 was converted to the hydroperoxide 111-35 (85%)

yield), ethyl benzoate (7% yield) and 111-34 (10% yield). No dioxetane was detected in the 'H

NMR spectrum (Scheme 3.15). The total yield of the [2+2] cycloaddition products is 13%

determined by GC. The photooxygenation 'H spectra were analyzed using the aforementioned

approach (section 3.4.2.1) with the aid of the COSY correlations (Figure 3.25). The olefinic

protons B^ and B'* resonate at 6.03 ppm and 5.76 ppm with a coupling constant of 16 Hz,

indicating the E-configuration. Unlike the photooxygenation of 111-25, where the TPP- backbone proton signals stay nearly unchanged, the proton 5^ signal of 111-35 shifts a noticeable 0.13 ppm upfield to 8.37 ppm compared to 8.50 ppm of 5^ in 111-26. The chemical

shift of the side-chain phenyl proton B^ increases from 7.50 ppm for 111-26 to 7.69 ppm for III-

35. It is notable that no [4+2] cycloaddition of singlet oxygen to the styrene-type moiety of

111-26 was observed. Normally the conjugated triene of the endoperoxide products of the [4+2] cycloaddition shows a series of characteristic proton signals between 4.5 ppm and 6.0 ppm,' and no new peaks can be detected in this region of the photooxygenation spectra. The ESI-MS analysis of the final crude mixture showed peaks of 880.9 m/e and 901.4 m/e, corresponding to M+H and M+Na for 111-35. The existence of 111-34 is confirmed by the 729.6 m/e peak

(M+H).

9 0 8,0 7.0 6.0 5,0 4.0 3.0 2.C 1.C ppm(t1)

Scheme 3.15 'H NMR spectral sequence of the photooxygenation of 111-26 (CÔDÔ, 400 MHz) 4 h 1.0

2.0 Ô O o

h 3.0

h 4.0

h- 5.0

0 6.0

K7.0

3 h 8.0 3 — 9.0 -ppm (t1

90 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1 0 ppm (t2)

Figure 3.25 COSY spectrum of the photooxygenation crude mixture of 111-26 (CeDe, 400

MHz, 22 min irradiation) 3.4.2.3 Photooxygenation of BPD-Ethyl Benzoate Complex 111-28

With the same "drug" (ester) molecule incorporated, 111-28 only differs from 111-26 by the photosensitizer moiety. Therefore, its photooxygenation result can be compared with that of 111-26 to see how different photosensitizers affect the drug-release outcome. The photooxygenation of 111-28 was carried out in CeDf, and de-acetone respectively and the results are summarized in Table 3.7, which are very similar to that of 111-26 as the "ene" reaction predominates in the photooxygenation. Since 111-28 consists of a pair of enantiomers, the suprafacial "ene" reaction taking place on either the top face or the bottom face of the enol ether plane, results in four diastereomers as two pairs of enantiomers labeled as III-

36X(±) and lll-36Y(±), at nearly a 1:1 ratio. It should be made aware that the designations of

X and Y are interchangeable and not necessary bound to the exact stereo-configuration as shown in the structures at Table 3.7. Table 3.7 Photooxygenation of 111-28

111-28 III-36X III-36Y (±) (±) (±) Entry Solvent^'^T' Conc Time Conv 111-36 ; X:Y ^ Ester(%) 1 (mM) (min) 1 (%) (%) 1 1 (byGC)" ^'50 "189'^' 7r 10 "2" j de-acetone 6 ' 80 ' "; ' >95^ "1'"i-T^r 15 " For both experiments, molar ratios of the substrate (based on A'' of 111-28) to the internal standard (based on IS"), conversions and yields (based on 100% conversion) were determined by 'H NMR spectroscopy. * Determined by GC peak area ratios and calculated using Equation 3.2, F= 1.20. Based on A' of 111-28. Based on A" of 111-28. " Based on B' and Cof III-36X and III-36Y. ^Based on 7' of 111-36. ^ Based on -OOH of 111-36.

The 50 minute photoirradiation in CeDe converted 89% of 111-28 to hydroperoxides

111-36 (71% yield) and the [2+2] cycloaddition products (10% yield determined by GC) (entry

1). The step-by-step NMR spectral sequence and the COSY spectrum of the final reaction

mixture are shown in Figure 3.26 and Figure 3.27. The progress of the photooxygenation is

evident by the gradual decrease of the signal of 111-28 at 7.53 ppm and the gradual increase

of the overlapped signals from B^and C'^ of III-36X/Y at 7.76 ppm. The olefinic protons of III-

36XA' appear at 5.93-5.84 ppm for B^/C^ (overlapped) and 6.12-6.04 ppm for BVC^

(overlapped), and the latter peaks also overlap with the 3^'' proton signals. The E-

configuration is confirmed by the coupling constant of 16 Hz. Two bonds away from the new stereocenter, the methylene resonances of B'°/C"^ appear as complex multiplets at 3.90-3.78

ppm and 3.65-3.54 ppm, in contrast to the quartet of A'° at 3.63 ppm. The singlets at 8.65

ppm and 8.25 ppm were assigned to the -OOH in lll-SSXA'. It is remarkable that the vinyl

group at 3 and the diene moiety at 7^ through 8 remained untouched during the singlet

oxygenation. Indeed, proton signals of these alkenes in lll-SGXA' have been assigned as

follows: the 3-vinyl proton signals of III-36X/Y appear at 8.39 ppm (3' of X), 8.21 ppm (3' of

Y), 6.39 ppm (3^' of both X and Y, overlapped) and 6.15-6.05 ppm (3^'' of both X and Y,

overlapped); 7^ signals of the dienes in III-36X/Y appear at 7.94 ppm (overlapped) while 7"*

signals are masked by the solvent peak at 7.16ppm. The nonreactivity of the diene can be

ascribed to the electron deficiency caused by the carboxyl group at 7^. The preservation of 3- vinyl group is not unprecedented as the vinyl group of vinylpurpurin was preserved in the

[2+2] singlet oxygenation reaction to make methoxalylpurpurin in Woodward's total synthesis of chlorophyll (section 1.4).^^ B7C -OOH S^b-XY of Y g10b/QlOb 73-XY B'*/C'' -OOH B3/C3 g10a/QlOa A o1 V I i il / 3l) •lJj 1/1

AJJU W_7 A •"1 r 1—r 8.0 7.0 6.0 5.0 4.0 3.C 2.G

Figure 3.26 'H NMR spectral sequence of the photoirradiation of 111-28 (CeDô, 400 MHz) I I I 11 1 1 I i ; 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.C ppm (t2)

Figure 3.27 COSY spectrum of the photooxygenation crude mixture of 111-28 (C^De, 400

MHz, 50 min irradiation)

The 80 minutes photoirradiation of 111-28 in d^-acetone (entry 2) gave similar results to those of entry 1. The "ene" products were generated in 63% yield with absolute E- selectivity. The ethyl benzoate was produced in 8%o yield based on the integration of the orf/îo-proton of the ester. The overall dioxetane yield was determined to be 15% by GC, slightly higher than that of entry 1. The -OOH signals of III-36X/Y appear at 10.49 ppm and

10.47 ppm as two singlets. As was the case in entry 1, the 3-vinyl and the diene in the

periphery of 111-28 did not react with singlet oxygen during the photooxygenation. The NMR

spectral sequence of the photooxygenation process as well as the COSY spectrum of the final

photooxygenation mixture are presented in Figure 3.28 and Figure 3.29 at the end of the

chapter.

In both cases, photooxygenation by-products, in small amounts, are observed in the

spectra. However, it is difficult to confirm their structures due to weak signals and

overlapping with other peaks. Most of the chlorin backbone signals remained unchanged

during the reaction. The generation of III-36X/Y was confirmed by peaks of 939.4 m/e (M+H)

and 961.4 m/e (M+Na) in ESI-MS spectra of both reactions.

3.4.2.4 Pliotooxygenation of TPP-Methyl Pivalate Complex 111-27

The photooxygenation of 111-27 (5 mM) was carried out in CeDe (Scheme 3.16). The

COSY spectrum of the crude reaction mixture after 25 minutes irradiation is shown in Figure

3.30. A total of 67 minutes photoirradiation of 111-27 gave an E-configured hydroperoxide III-

37 (58% yield, J = 16 Hz), dioxetane 111-38 (19% yield) and 111-34 (2% yield). The olefinic protons of 111-37 appear as a triplet-triplet at 5.87 ppm (B^) and a doublet at 5.47 ppm (B").

The singlet of 6.95 ppm is assigned to -OOH of 111-37. The proton signals of the dioxetane appear at 5.55-5.51 ppm for C^ 3.79 ppm for C^ and 1.03 ppm for C'. ESI-MS spectrum of the final crude mixture shows peaks of 867.4 m/e and 729.5 m/e, corresponding to the formulas of M+Na for 111-37 and M+H for 111-34 respectively. The fact that the "ene" reaction still predominates in this photooxygenation indicates that the steric hinderance of the bulky t- butyl group failed to hamper the attack of the small-sized singlet oxygen on the a-carbon to which it is attached. Therefore, attempts to control the chemoselectivity or regioselectivity of the singlet oxygenation merely through the steric hinderance should be avoided.

9.0 8.0 7,0 8.0 5,0 4,0 3.0 2.C 1.C ppm (t1 ) Scheme 3.16 H NMR spectral sequence of the photooxygenation of 111-27 (CÔDÔ, 400 MHz

and 300 MHz) i I \ 1 \ i \ { \ 1 1 i j I—I—\—i—[—\—I—i—\—^—I—i—\—i—^—r 6.0 5.0 4.0 3.0 2.0 1.0 ppm(t2)

Figure 3.30 COSY spectrum of the photooxygenation crude mixture of 111-27 (CeDe,

400 MHz, 25 min irradiation)

3.5 Summary

A series of photosensitizer-drug complexes have been successfully synthesized using the first generation linker 111-15. Esters as drug mimics were first attached to one end of the linker molecule to form an enol ether linkage by Takai alkylidenation and the other end was then connected to photosensitizers via an ester bond. All of the four complexes were subject to the photooxygenation and the products from the "ene" reaction and the [2+2] cycloaddition reaction were usually observed. The success of the photooxygenation indicates that the singlet oxygen reactions take place as usual even when the olefin substrates are directly linked to photosensitizers. Interestingly, no singlet oxygenation occurred to the photosensitizer moieties

(photobleaching) in our experiments, including the benzoporphyrin in which vinyl and diene groups are present. Esters (drugs) have been successfully released from the complexes upon photoirradiation in yields from less than 5% to as high as 60%. Unfortunately, the "ene" reaction dominated in most cases, it is highly desirable to seek a new sfrategy to build complexes with the high chemoselectivity towards the [2+2] cycloaddition upon photoirradiation. 30 mins

7 mins

0 min "1 r 10.0 5.0 O.C ppm (ti)

Figure 3.21 'H NMR spectral sequence of the photooxygenation of 111-25 (de-acetone, 400 MHz) T I j i 1 I I ^ 1 I ] \ j I ] 1 1 1 ] 1 ] 1 j 1 ] 1 1 1— 60 5.0 4.0 3.0 2.C 1 0 ppm (f2) 240 mins

90 mins

0 min

10.0 5.0 0.0 ppm (f1)

Figure 3.23 'H NMR spectral sequence of the photooxygenation of 111-25 (CD2CI2, 400 MHz, -78°C) 6.0 5.0 4.0 3.0 2.0 1.0 ppm(f2) Jb 80 mins

1 15 mins

uu y 2 mins

UUuf È JL. IIJ iii 0 min "I j r 1 r 10.0 5.0 O.C ppm (ti)

Figure 3.28 'H NMR spectral sequence of the photooxygenation i xJiJLJLiLjL lu

h 5.0

— 10.0 ppm (t1

10.0 ppm (t2) CHAPTER FOUR

Building Photosensitizer-Drug Complexes with

Second Generation Linker Using Takeda

Alkoxymethylenation 4.1 Design Strategy

4.1.1 General Consideration

As detailed in Chapter One, the [2+2] cycloaddition of singlet oxygen is generally

limited to electron-rich olefins such as enol ethers, enamines and vinyl sulfides. For enol

ethers, the [2+2] cycloaddition generally competes ineffectively with the "ene" reaction and

the [4+2] cycloaddition, although a few exceptions exist." This drawback persists in our

singlet oxygenation of porphyrin or chlorin derivatives bearing peripheral enol ether moieties

(Chapter Three). With increased electron density of the double bond, enediol ethers are prone

to have the [2+2] cycloaddition mode predominate in their singlet oxygenation reactions, as

indicated by abundant experimental facts'*''' '°^' ''^^"'''^ (Scheme 4.1). In all these reported

reactions, dioxetane products either decompose spontaneously during irradiation or later by heating to give carbonyl fragments (esters or carbonates). It is noteworthy that the [2+2] cycloaddition seems to dominate regardless of the stereo-configuration at the double bond. -OEt hv, O2, sens ^ o- Ref. 2 (quantitative) -78°C, CFCI3 I "^OEt Q- ^OEt

EtO- ,.^OEt hv, O2, sens 0-1 (quantitative) Ref. 2 -78°C, de-acetone OI " -QEt ^OEt

hv. O7. sens Ç-^-OEt (quantitative) Ref. 3 -70°C, de-acetone O""y-QEt EtO OEt OEt

Ph^ /OMe hv, Oy, sens 9^0Et (QQo/^j p,^^^ ^ Ph' ~OMe '•.t., 85% ether+15% MeOH O^OEt Ph Ph hv, O2, sens 'OEt (75%) Ref. 4 'r.t., 85% ether + 15% MeOH Q-^OEt Phx^/OMe Ph

MeO Ph hv, O2, sens I. (96%) Ref. 5 r.t., acetone MeO Ph

.0. hv, O2, sens °\ /—\ P r.t., acetone /—O 0—\ (quantitative) Ref. 5 ^O" H H

.O.^F1i hv, O2, sens (91%) Ref. 5 T r.t., acetone ^O Ph Ph Ph

OOH O hv, O2, sens (75%) + (25%) Ref. 6

pSiMe2R .OSiMe2R hv,02,sens ° (100%) Ref. 7 O -20°C, CCI4 ^^ï>^o \ °

(sens = photosensitizer)

Scheme 4.1 Singlet photooxygenation of enediol ethers

Enamines are highly reactive towards singlet oxygenation with a rate constant just two orders of magnitude below that of diffusion control. The typical rate constants for singlet oxygenations of an enamine, enediol ether and enol ether are presented in Table 4.1."^

Moreover, a complete chemoselectivity of the [2+2] cycloaddition over other modes is

generally observed in enamine photooxygenation. Some examples'^^"'^°' are shown in Scheme

4.2. The resulting a-amino dioxetanes are more labile compared to the a-alkoxy dioxetanes derived from the photooxygenation of enol ethers and the decomposition products are usually collected after the irradiation. It is notable that a new decomposition pathway via the cleavage of the C-N bond rather than the C-C bond of the dioxetane is observed in the photooxygenation of enamines with a /S-hydrogen or an a-phenyl group. The decomposition of dioxetane is beheved to involve a biradical mechanism (Scheme 4.3).^^^ The labile 0-0 bond is broken homolytically to give a biradical species, followed by the C-C bond cleavage or the competitive C-N bond cleavage, considering the C-N bond energy is generally 10 kcal mol"' lower than that of the C-C bond. The C-C bond cleavage leads directly to the carbonyl products while the C-N bond cleavage generates a keto alkoxy radical IV-1, which can be converted into either an a-hydroxylketone via H-abstraction or an o!-diketone via a C-C bond fragmentation.

Table 4.1 Reactivities of different olefin subsfrates towards singlet oxygenation

Entry I Olefins T Solvent i kr{ M"' sec'')" Me 1 >>==A \ ' benzene i 4.9x10^ Me NMe2 2 ^X /- \,-.\ acetone ^ 4.7 xlO' EtO OEt /--\ 3 i QO O ' acetone ! 2.2 x 10 \ _y "^gj I acetone j 2.9x10^

' Ref. 8 unfortunately does not list the reaction temperature used. hv, O2, sens o-\ (quantitative) Ref. 9 CsHe

hv, O2, sens (quantitative) Ref. 10 15°C, methanol O +

O o

hv, O2, sens (90%) Ref. 9, 11 r.t., CeHe N —

hv, O7, sens Ph, 0=\ (90%) Ref. 9 O N Ph

hv, O2, sens Ph 0=A ho (quantitative) Ref. 12 20°C, pyridine Ph

O

hv, O2. sens O, /— HO /— 20°C, pyridine r=0 + 12

(69%, from C-C cleavage) (31 %, from C-N cteavage)

Ph hv, O2, sens 0^ O Ph HO Ph other .,2 20°C, pyridine /=0 + products o ^ o -o V (29%, from C-C cteavage) (71 %, from C-N cteavage)

Ph H9 Ph hv, O?, sens ^ \_ "^^N other Ref. 12 20°C, pyridine / *"* products O

(68%, from C-C cteavage) (32%, from C-N cteavage)

Scheme 4.2 Singlet photooxygenation of enamines Scheme 4.3 Mechanism of the ûf-amino dioxetane cleavage

With a strong electron-donating sulfur substituent, vinyl sulfides are highly activated towards singlet oxygenation. A variety of vinyl sulfides have been oxidized by singlet oxygen and give the [2+2] cycloaddition products predominantly, if not exclusively (Scheme 4.4).^^'

202-204 gjjj^ji^j. ti^^^ Qf o(_ainino dioxetanes, the decomposition of a-thio dioxetanes can undergo either C-C bond cleavage or C-S bond cleavage and the latter generally predominates due to the low strength of the C-S bond (65 kcal mole"') compared to that of the C-C bond (83 kcal mole"'). Following a similar mechanism as depicted above (Scheme 4.3), the cleavage of the C-S bond gives a mixture of a-hydroxycarbonyl compounds, a-dicarbonyl compounds, etc.

In addition, sulfides themselves can be oxidized by singlet oxygen to sulfoxides and therefore a small amount of sulfoxides were observed in the photooxygenation of some thioethylenes. Mes, SMe i.hv, ^O^. CH2Cl2.-70°C ^^^^^O Ref. 15 2. r.t. SMe MeS SMe Mes O

EtS^O ^*S, ^Ët hv, ^Oy, acetone_ (67%) + (7%) ' \ r.t, 1 hr ^ Ref. 16 EtS SEt 90% conversion EtS ÇEt (63%) + 1 V EtS SEt C-S deavagle y C-C deavagle

EtS-,^0 EtS SEt hv, acetone. ^'^Y° + + A + sufoxide .jg / \ r.t, 1 hr * EtS H 55% conversion EtS O SEt EtS SEt and others '^^'^ '° (3%) (19%) (32%) (1%) (1-2%) V , J ~ , Y C-S cleavage C-C cleavage

PhS / hv, ^Oy, MeOH ^Ph etc. Ref. 16 r.t., 80% conversion OH SPh PhS

(8%) (18%) (22%) (22%)

C-S deavage C-C deavage

H^O hv, ^O;, MeOH etc. Ref. 17 r.t. •OH SEoc*t t-.y^r.. H Bu Et Et" Bu Bu (4%) (26%) (65%)

C-S deavage C-C deavage

9 hv, ^02, MeOH Et ^ Ref. 17 r.t. SEt Et Bu (4%) (2%) (65%) (16%;

C-S deavage C-C deavage sulfoxide

Scheme 4.4 Singlet photooxygenation of vinyl sulfides

As we continued to seek strategies to synthesize photosensitizer-drug complexes which could release drug in high yield with simpler photooxygenation byproducts upon photoirradiation, linkages made of enediol ethers, enamines or vinyl sulfides looked promising. Since the [2+2] cycloaddifion of singlet oxygen to the olefin linkage followed by C-C bond scission of the resulting dioxetane are the pivotal steps of our drug-releasing

strategy, the alternative C-S or C-N decomposition pathways are rather discouraging for such

purpose. Therefore, we focused on the development of synthetic approaches to incorporate

drugs through enediol ether or enamine linkages (C-N cleavage in the photooxygenation of

enamines only occurs with certain substrates to a small extent).

4.1.2 Takeda Alkoxymethylenation Leading to the Enediol Ethers or Other j8-Hetero-

Substituted Enol Ethers

Traditional Wittig-type alkoxymethylenation using a-phosphorus or a-silyl carbanions bearing an o:-alkoxy group suffers the drawback of ineffectiveness towards carboxylic acid derivative substrates. Therefore, the synthetic route to prepare highly electron-rich 1,2-diheteroatom substituted 1-olefins from carboxylic acid derivatives awaited discovery.

The first solution emerged soon after the discovery of the thioacetal-Cp2Ti[P(OEt)3]2 system for the alkylidenation of carboxylic acid derivatives by Takeda and coworkers (section

3.13, Chapter Three). In a follow-up investigation, they found that dithio- and trithioorthoformates can be used as carbene complex precursors to convert carboxylic acid derivatives into 1,2-diheteroatom substituted 1-olefins following the general mechanism illustrated in Scheme 4.5.^°' However, the inaccessibility of various dithioorthoformates hampers its application as a general methodology. CpaTiClz

P(0Et)3 Mg, 4A molecular sieves

Cp2TI[P(OEt)3]2 1 CP2T III-6 Ri ZR2 ,Ph Y "-TiCp2 -ZR, Y

- Cp2Ti=0

ZR2 Y= OCH3, SPh; Z= C, O, S R

Scheme 4.5 Takeda olefination using dithio- or trithioorthoformates

On the other hand, further investigation of alkylidenation using alkyl halides as carbene complex precursor (detailed mechanism see Scheme 3.9, Chapter Three) by the same group revealed that alkoxymethyl chlorides are applicable substrates. Consequently, a number of enol ethers and enediol ethers have been synthesized (Scheme 4.6).^°^ Since alkoxymethyl chlorides can be readily prepared from the corresponding alcohols with paraformaldehyde and

HCl gas, this method provides a general synthetic route to enediol ethers, hi contrast to the Z- selectivity of the alkylidenation of esters using alkyl halides, the present alkoxymethylenation shows modest E-selectivity, which is ascribed to unfavorable dipole-dipole repulsion between the two alkoxy groups in the oxatitanacyclobutane intermediate along the Z-selective reaction pathway. The disadvantages of this method include the harsh condition (HCl) in the starting material preparation and the use of more than two equivalents of alkoxymethyl chlorides.

Esters are the only carboxylic acid derivatives that have been tested using this methodology. Cp2TiCl2

P(OEt)3 Mg, 4A molecular sieves

Cp2Ti[P(OEt)3]2 III-6 X RO CI RO ^TiCp2 - Cp2Ti=0 '

Y= C, O

Scheme 4.6 Takeda alkoxymethylenation using alkoxymethyl chloride

In 2004, Takeda solved the inaccessibility problem of dithioorthoformates possessing various alkoxy groups by a CuBr2-promoted oxidative coupling between a-stannyl thioacetal

IV-2 and alcohols.'^* The mechanism of dithioortho formate synthesis and its subsequent transformation is proposed by Takeda as depicted in Scheme 4.7."'* IV-2 is readily prepared from the reaction between tributyltin chloride and bis(phenylthio)methane. An alcohol is converted to an alkoxycopper(II) species after its deprotonation by butyllithium and the reaction with copper(II) bromide. Transmetallation reaction between IV-2 and the alkoxycopper(II) species ftimishes the alkoxy bis(phenylthio)methylcopper(II) species IV-3. A single-electron oxidation of IV-3 followed by the reductive elimination of the resuUing trivalent organocopper species IV-4 gives dithioorthoformate IV-5. The subsequent alkoxjmethylenation using IV-5 follows the general mechanism of Takeda alkylidenation using a titanocene-carbene complex. A wide range of carboxylic acid derivatives including esters, lactones, thioesters, and amides have been converted to enediol ethers or other /S- hetero-substituted enol ethers using this methodology. The stereoselectivity of these reactions is poor and a moderate E-selectivity is observed in some cases. ?Ph LDA JP^ CISnBua + SPh THF BusSn SPh IV-2

SPh SPh

ROH ^ ROLi -LiBr ROCuBr -BuaSnBr ROCu(lROCu(Ml )Ap SPh h _ ^^^^ '^O^Cu^SPCu SPh IV-3 Br IV-4

- CuBr

Cp2Ti[P(OEt)3]: •YR, CP2T -c X RO Ri YR2 , Utfi -YRo RO ~"TiCp2 Ri - Cp2Ti=0 RO' RO' SPh IV-5 Y= C, O, S, N

Scheme 4.7 Synthesis of dithioorthoformates for Takeda alkoxymethylenation

4.1.3 Synthetic Approach for Photosensitizer-Drug Complexes Bearing Enediol Ether

or Other /3-Hetero-Substituted Enol Ether Linkages

As discussed in section 4.1.1, enediol ether substrates exhibit superior [2+2] cycloaddition selectivity in singlet oxygenation, and this would be expected on other /3- hetero-substituted enol ether substrates as well. It is desirable to have such linkages appearing at the A terminus of the linker molecule after drug attachment to facilitate drug release

(section 3.2, Chapter Three). As introduced in the last section, Takeda alkoxymethylenation using dithioorthoformates provides a simple and general entry to enediol ethers and their analogues and therefore can be adopted for this purpose. As a result, a dithioorthoformate functionality is required at terminus A, which can be readily prepared from the corresponding alcohol. If we use the same strategy for photosensitizer attachment at terminus B by esterification as that of the first generation linker synthesis, it is straightforward that the new linker molecule can be readily prepared from a diol. As shown in Scheme 4.8, starting from the commercially available 1,5-pentadiol, after selective silyl protection of one hydroxyl group (terminus B) and the subsequent conversion of the other hydroxyl group to a dithioorthoformate moiety (terminus A), the second generation linker IV-7 can be generated.

Under the Takeda alkylidenation conditions, drug molecules bearing ester, thioester or amide groups can be incorporated through the enediol or other /J-hetero-substituted enol ether linkages at terminus A. After silyl deprotection and esterification with photosensitizer-acids, final complexes can be generated. The poor stereoselectivity of the Takeda alkoxymethylenation should not be a concern since either Z- or E-l,2-diheteroatom substituted 1-olefin should predominately undergo the [2+2] cycloaddition upon singlet oxygenation and generate the same cleavage products after the thermolysis of dioxetanes, based on the reported examples in Scheme 4.1.

"A"

Ph

IV-2 linker 1 SPh R^YR

TBDMSO -H?O^SPh • TBDMSO-H?0-V"«'i-^ HO^O^^^ 3 Cp2TiCl2,Mg, ^ LYR-J ' YR IV-7 P(0Et)3,4A MdSJHF ^

"prodrug moiety" coupler sensitizer

COOH

Y= 0, S, Nj

Scheme 4.8 Proposed synthesis of the linker IV-7 and final photosensitizer-drug complexes 4.1.4 Synthetic Approach for Photosensitizer-Drug Complexes Bearing Enamine

Linkages

In addition to the previous sequence, we envisioned another complex-synthesis strategy involving an enamine linkage simultaneously. We know that a single amino substituent can sufficiently activate olefins towards the absolute [2+2] cycloaddition selectivity in singlet oxygenation. It is plausible then to pursue a strategy to incorporate and release a drug molecule bearing a ketone functionality through an enamine linkage. The ketone can be readily converted to a one-carbon homologated aldehyde by a tandem process, i.e., a Wittig reaction with methoxymethylphosphonium to give an enol ether, followed by hydrolysis.^"' On the other hand, N,N'-dimethylethylenediamine can be employed as a linker to first join with a photosensitizer acid via an amide bond and then react with the aforementioned aldehyde to create the enamine linkage (Scheme 4.9). The photosensitizer attachment step occurs ahead of the drug attachment step in this design, due to the high lability to hydrolysis of enamines.

POOH

H N H linker sensitizer^ I

^ CHaOCHzPPhsCI hv R R' base drug release

Scheme 4.9 Proposed synthesis of photosensitizer-drug complex bearing enamine linkages 4.2 Synthesis of Photosensitizer-Drug Complexes Bearing Enamine Linkages

Nabumetone is a non-steroidal anti-inflammatory drug (NSAED). Since the isolation of salicyclic acid in early 19'*" century, NSAIDs have played an important role in the treatments of pain and inflammation. The simple structure of nabumetone makes it a good target compound to test our synthesis and release strategy. A Wittig reaction between nabumetone and triphenyl-(methoxymethyl) phosphonium chloride using LiN(SiMe3)2 as base gave a crude enol ether containing mixture, which was purified through a flash silica gel column and the enol ether IV-8 was collected and immediately subjected to HCl-catalyzed hydrolysis to furnish aldehyde IV-9 in 57% yield (over two steps). Separately, photosensitizer

111-21 was employed to prepare the amide IV-10. Steghch coupling agents such as DIC and

EDC were first used and a rather disappointing result (slow conversion, less than 30% yield after 2 days) was observed in either case. We then turned to the benzotriazol-uronium-based coupler IV-11, a powerful coupler widely used in sohd-phase peptide synthesis,^^* and an improved yield of IV-10 (51%) was achieved after stirring for 20 hours (Scheme 4.10).

(nrt produœd)

Scheme 4.10 Synthesis of photosensitizer-drug complexes bearing enamine linkages As shown in Scheme 4.11, the mechanism of our amidation reaction using benzotriazol-uronium-based coupler presumably starts with the activation of the acid to give a benzotriazol-ester, which is then attacked by the amine nucleophile to generate the amide product.

Unfortunately, the reaction between IV-9 and IV-10 to form the enamine linkage was unsuccessful. Various reaction conditions^°^'^'° for enamine synthesis were tried, including 1) refluxing in toluene using a Dean-Stark trap, 2) refluxing in toluene with TsOH catalyst and

4Â molecular sieves as water scavenger, and 3) vigorously shaking of the THF solution of reagents with 4Â molecular sieves by sonication at room temperature (4Â molecular sieves serve as catalyst as well as dehydrating agent in this case). However, only a trace amount of a new band was observed on TLC (both silica gel and alumina), if at all, in all the trials, hi fact, aldehyde enamine synthesis has long been regarded as a challenge for its high lability and difficulty of purification.^" Further efforts towards solving this synthetic problem were suspended as we resorted to our original strategy of complex synthesis (vide infra).

Scheme 4.11 Suggested mechanism of the amidation using the coupler IV-11 4.3 Synthesis of Photosensitizer-Drug Complexes Bearing Enediol Ether or Other /3-

Hetero-Substituted Enol Ether Linkages

Based on the synthetic roadmap proposed in Scheme 4.8, the synthesis of the second

generation linker started with the mono-silylation^'^ of 1,5-pentandiol using NaH as base and

IV-6 was produced in 62% yield, which was then converted to linker molecule IV-7 in 58%

yield by oxidative coupling with IV-2 using Takeda's protocol"** (including the synthetic

method of IV-2, details see Scheme 4.7).

In the following Takeda alkoxymethylenation of carbonyl compounds, Mg turnings,

Cp2TiCl2, and P(0Et)3 were first mixed in THF with the presence of 4Â molecular sieves to

generate the reactive titanocene(II) species III-6, followed by the addition of the linker IV-7

and the dropwise addition of carbonyl substrates after a 10 minute interval. The reaction was generally complete within 3 to 16 hours at reflux. The crude reaction mixture was then subjected to basic alumina (II) column chromatography and a mixture of Z/E isomeric products was produced in most cases. It was found to be better to carry them through to the next step without vigorous separation since the Z/E isomers of the final complexes are more easily separated. The stoichiometry of the reagents was 1:1.5:4.5:5.3:9 for carbonyl compound:IV-7:Cp2TiCl2:Mg:P(OEt)3. The reaction is highly moisture-sensitive and in addition to the dry solvent and standard Schlenk operations, solid reagents such as Mg and

Cp2TiCl2 need to be dried by heating under reduced pressure. A series of carboxylic acid derivatives as drug mimics were employed in this reaction, including ethyl butyrate, ethyl benzoate, ô-valerolactone, N-methylbenzanilide, 1-benzoylpiperidine, and N,N-dimethyl acetamide. Moreover, NSAIDs ibuprofen and naproxen were converted to their methyl esters IV-12 and IV-13 (H2SO4 catalyst, quantitative yield) and then attached to the linker IV-7 using the same reaction.

The alkoxymethylenation products were desilylated by TBAF and the resulting alcohols reacted with the carboxyl group of the photosensitizer 111-21 or 111-22 using EDC as coupler to give the final complexes. Z/E isomers of final complexes were separated by basic alumina (II) column or preparative TLC plates (silica gel). The results of Takeda alkoxymethylenation as well as the final esterifications are summarized in Table 4.2 Table 4.2 Takeda alkoxymethylenation and the final esterification

SPh R.-" YR -—~t • ' J

TBDMSO' M^O-^SPh Cp2TiCl2, Mg, linker P(0Et)3, 4A Mois,THF YR sens-cosens-COOo H YR IV-7 IV-14-IV-20 IV-21~IV-29

; Entry ^ Carbonyl substrates Takeda" | Yield* I Z/E ^ | Sens-^ 1 Complex^ > Yield^

0 1 TPP IV-21-Z/E IV-14-Z/E 56 39:61 85 ^O' ! BPD IV-22-Z 53 O i ; o IV-15-Z/E 38 I 91:9 I TPP IV-23-Z 96

IV-16-Z/E 72 I 40:60 j TPP | IV-24-Z/E 88 i _ ^ I

TPP I IV-25-Z/E 95 IV-17-Z/E 62 : 63:37

IV-12 from Ibuprofen BPD t IV-26-Z/E^ 58

TPP Î IV-27-Z/E I 80 IV-18-Z/E ! 40 61:39

IV-13 from Naproxen BPD i IV-28-Z/E^ I 58

0

N' IV-19-Z/E i 51 83:17 TPP I IV-29-Z/E 81

N IV-20-Z/E 26 92:8 : n/a n/a n/a

O

n/a n/a n/a I n/a n/a n/a anatt of Ï^R^ alkoxymethylenation products. ^ Isolated yaeld ^ Z/E deternnned by s^^^^^^^^^ Zl'I f NMR spectra and the ratio determined by NMR mtegration. " TPP = 111-21 and BPD = 111-22 = Labe s of the fmal photosensitizer-drug complexes. ^Isolated yield (%). * Mixture of diastereomers The ester substrates including aliphatic esters, aromatic esters and lactones were

successfully alkoxymethylenated in yields ranging from 38% to 72%. The reaction is not

apparently sensitive to steric bulk. In fact, a-branched methyl esters of ibuprofen and

naproxen were alkoxymethylenated in comparable yields (entries 4 and 5). Aromatic ester

ethyl benzoate however gave only 38% yield after the reaction (entry 2). It should be noted

that only isolated yields are reported and the low yields can also be attributed to the

decomposition of product during the purification process rather than the poor reactivity. This

is especially true for the reactions of amide substrates. The isolated yields decrease from N-

methylbenzanilide (51%, entry 6) to 1-benzoylpiperidine (26%, entry 7) and for N,N-dimethyl

acetamide, only hydrolysis product was observed after the work-up (entry 8). Furthermore,

the desilylation of IV-20 failed as the resulting alcohol is too unstable to be purified. The high

susceptibility towards hydrolysis of the enamine products adds unpredictability to the general

application of this method to deliver drugs bearing amide groups.

The stereochemistry of the alkoxymethylenation products can be assigned by field-

effect analysis of the 'H NMR spectrum of the mixture of diastereomers, in addition to the

NOE experiments. For example, in the 'H NMR spectrum of a Z/E mixture of IV-17, the

chemical shifts of protons spatially close to the oxygen atoms are greatly affected for both

isomers (Scheme 4.12). For the olefinic proton-a, it is relatively close to the methoxy oxygen

in the E-isomer but not in the Z-isomer, and thus the lower field olefinic signal with lower integration is assigned to E-a. Such assignments can be fixrther confirmed by the comparison of proton signals of b, c and d from both isomers. Since the NMR spectrum of a certain compound is actually the weighted-average of the spectra from its fast a-rotating confonners, two representative conformations of each diastereomer derived from the rotation along the Cd- Ce ff-bond are presented here. For the phenyl proton-b in IV-17E, there is a vicinal oxygen atom in each conformer while this scenario only exists in one conformer of IV-17-Z.

Therefore proton E-b resonates at a lower field than Z-b. Similar field-effects also explain ô

Z-c > Ô E-c and ô E-d > ô Z-d.

IV.17-E

E-c

Z-b Z-a E-b E-a ,Z-d E-d

7,0 6.0 5.0 3.C ppm(fl)

Scheme 4.12 Stereochemistry assignments for IV-17-Z/E by the field-effect analysis of 'H

NMR spectrum of the mixture (CôDe, 400 MHz) As is obvious from our results, the stereoselectivity of Takeda alkoxymethylenation

is highly structure-dependent. A high Z-selectivity was observed in reactions of tertiary

amides. Aromatic esters and steric demanding esters gave moderate Z-selectivity. On the other hand, sterically less demanding aliphatic esters and lactones showed moderate E-selectivity.

This phenomenon can be tentatively ascribed to the opposing effects from steric repulsions

and the hetero atom-hetero atom dipole repulsions. The former favors the Z-product while the latter leads to the predominant E-product.

Products from the desilylation of the drug-linker conjugates were immediately carried forward to the final esterification reaction after flash chromatography over a basic alumina (III) column. TPP-based 111-21 was used to build the final complexes with all the incorporated drugs or mimics and BPD-based 111-22 was employed in the synthesis of complexes bearing incorporated ethyl butyrate and the methyl esters of two NSAIDs. EDC was employed as coupler in all cases and similar yields of esterifications to those presented in

Chapter Three were observed.

The final complexes have been characterized by 'H NMR, '^C['H] NMR (except for

IV-26-E, IV-27-E, and IV-28-Z/E), MS and UV-Vis. The complete peak assignments for 'H and '^C['H] NMR spectra of the final complexes have been greatly facilitated by referring to the assignments of structurally analogous first generation complexes in Chapter Three and the same approach of combining COSY, HMQC and HMBC techniques is adopted. Despite the fact that the starting materials IV-12 and IV-13 are racemic and optically pure respectively and should lead to four diastereomers as two pair of enantiomers for each of IV-26-Z/E or one pair of diastereomers for each of IV-28-Z/E, 'H NMR spectra of all the diastereomers completely overlap for IV-26-27E and IV-28-Z. And for IV-28-E, two diastereomers can be distinguished by slight chemical shift differences regarding certain protons in their 'H NMR

spectrum (mixed at 1:1 ratio). The substantial peak overlaps of the final complex

diastereomers are due to the fact that the chiral carbon in the drug moiety is located far from

the chiral carbons 7 and 7' on the BPD-backbone and therefore the respective magnetic micro

environments are insensitive to the remote chiral center.

UV-Vis spectra of all final complexes are essentially the same for each type of

chromophore, since the chemical modifications only occurred to the side-chains of the involved porphyrinoids and the conjugated macrocycle systems are not affected.

4.4 Photooxygenation of the Second Generation Photosensitizer-Drug Complexes

The Photooxygenation of the second generation photosensitizer-drug complexes were carried out following the same experimental settings and procedure as introduced in section

3.4.1. 1,3,5-Trimethoxybenzene was employed as internal standard in all cases. Interestingly,

Z-isomers and E-isomers of the complexes showed dramatically different results as the former gave nearly quantitative [2+2] cycloaddition products as desired while the latter gave the

"ene" reaction products predominantly. All proposed porphyrin- or chlorin-based products have been confirmed by ESI-MS.

4.4.1 Photooxygenation of Photosensitizer-Ethyl Butyrate Complexes Bearing Enediol

Ether Linkages

The resuUs of photooxygenation of IV-21-Z and IV-22-Z at room temperature are summarized in Table 4.3. Four different solvent systems, including CÔDÔ, CDCI3, CDCI3

(with 20% MeOD), and de-acetone, were used to evaluate the solvent-dependency of the

photooxygenation of the second generation complex IV-21-Z. It turned out that [2+2]

cycloaddition completely predominated the photooxygenation to give dioxetane and its

cleavage carbonyl products in quantitative yield, regardless of solvent (entries 1, 2, 3, and 4-

3). Dioxetanes mostly decomposed spontaneously during the photoirradiation, except in

CDCI3 (entries 2 and 3) where about 70% remained after the photoirradiation and slowly

decomposed within hours. Compared to those described in Chapter Three, the

photooxygenation of new-generation complexes appear to be a much quicker process. Most of

them were completed within 5 minutes, which is in stark contrast to the 30 to 50 minutes reaction time in Chapter Three. This can be attributed to the increased electron-density of the

double bond provided by the extra alkoxy group, which facilitates the attack of the

electrophilic singlet oxygen. To verify the involvement of singlet-oxygen in these photooxygenation reactions, l,4-diazabicyclo[2.2.2]octane (DABCO), a singlet oxygen quencher,'" was added to a photooxygenation system of IV-21-Z in de-acetone and stepwise results of the photooxygenation with or without DABCO quencher are presented as entries 4-

1 to 4-3 and entries 5-1 to 5-4 for comparison. The involvement of singlet oxygen was undoubtedly confirmed as the presence of DABCO greatly suppressed the progress of the photooxygenation. Without the quencher, the conversions of the complex were 35%, 68% and

>95% after 1, 5 and 8 minutes of the photooxygenation; while with the presence of DABCO, they were reduced to <5%, 24% and 40%o respectively. It took one hour to complete the photooxygenation and the carbonyl compound IV-30 and ethyl butyrate were generated in quantitative yield (entry 5-4). Table 4.3 Photooxygenation of IV-21 -Z and IV-22-Z

IV-21-2 (BPD-based) IV-22-Z{±)

Solvent Conc ! Time * Conv ; Diox Tcïeav total l2+2]^ Entry" i Complex '^'Ester (%)^ (additive) (mM) 1 (min) i (%)* ; (%)^ 1 (%)" (%) ' (byGC)^ 1 IV-21-Z r >95 •[ "'"71"''^ 94 2 ' IV-21-Z CDCI3 \ " 3'^^ i 70 T21' '"^^1^ >95'~ CDCI3: 3 IV-21-Z 4 j >95 20 93 >95 MeOD=4:l i 73 1 35 34 ; 44 4-2 ' IV-21-Z ! dfi-acetone 4 ri ^ r"3o'"^" r 40' " 70 i "'"^>95'"^'' 4- 3 Y' >95 ^^'>95^ 'Y 1<5" <5%'' 0 de-acetone : 24 14" i ^20 " 24"1 'I4 IV-21-Z 5- 3 (DABCO) !"40 '20 ; 26 46 34 60 1 >95 ^ Ô >95 \ >95

1 IV-22-Z 5 i >95 '^84^ 90 ! 85 acetone=5:l 5 1 6 " Ail the experiments were carried out at room temperature and the molar ratios of the substrate (based on A^j to the internal standard (based on the aromatic proton), conversions and yields (based on 100% conversion) were determined by 'H NMR spectroscopy. * Conversions based on A*. " Yields of dioxetanes based on B*. Yields of the cleavage products. " Total yields of the [2+2] cycloaddition, the sum of the dioxetane yield and the cleavage product yield. -'^Determined by GC peak area ratios and calculated using Equation 3.2, F= 0.78. ^Stepwise photooxygenation results are presented as entries 4-1, 4-2 ... for comparison. DABCO (6 eq.) was added to the photooxygenation system and stepwise photooxygenation results are presented starting as entries 5-1, 5-2 ... for comparison.

A step-by-step NMR spectral sequence of the photoirradiation of IV-21-Z in CÔDÔ is

shown in Figure 4.1 as a representative case. The peaks were assigned with the assistance of the COSY spectrum (Figure 4.2) as in Chapter Three. The gradual consumption of IV-21-Z

(as evident by A^, A**, etc.) was accompanied by the emergence of the [2+2] cycloaddition products. There are some weak signals in the NMR spectrum appearing to be from the hydroperoxide but can not be confirmed. The sequential spectra as well as the COSY spectra of the photooxygenation of IV-21-Z in other solvents are presented at the end of this section from Figure 4.3 to Figure 4.7 for reference (in the same order as presented in Table 4.3).

* presumed signals from the hydroperoxide ("ene" product)

4 mins

2.5 mins

1 min

0 min

Figure 4.1 'H NMR spectral sequence of the photooxygenation of IV-21 -Z (CeDe, 400 MHz) n~~r~ryT~rT^T~prTT~T"| i i i i [ i i i i j i i i i i i ~nry~rTT~npr~rT~T 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 ppm (t2)

Figure 4.2 COSY spectrum of the photooxygenation crude mixture of IV-21 -Z (C^Df,, 400

MHz, 4 min irradiation).

The photooxygenation of IV-22-Z in a mixed solvent of CôDe :d6-acetone = 5:1 was completed within 5 minutes (entry 6, Table 4.3). NMR showed the [2+2] cycloaddition products (IV-31, IV-33-Z, and the ester) were produced in 90% yield, together with a by• product (in ca. 6% yield) presumably to be the hydroperoxide from the "ene" reaction (Figure 4.8). Similar to the photooxygenation of its TPP analogue, the proton signals of the

macrocycle backbone essentially were intact. Most of dioxetane IV-33-Z remained during the

photoirradiation and slowly decayed over time. In theory, IV-33-Z should be generated as two

pairs of enantiomers. However their 'H NMR signals completely overlap due to separation

between the dioxetane ring and the BPD chiral centers. The singlet at 5.79 ppm was assigned

to B'' and the dioxetane as the major product was confirmed by the equivalent GC yield (85%).

IS IS * presumbed signals from the hydrqieroxide ("ene" product)

c« D2

JLl! v_ 5 mins

1 min

JU 'UL 0 min

9.0 8,0 7.0 6.0 5.0 4.C 3.0 2,C 1,C ppm (ti) Figure 4.8 H NMR spectral sequence of the photooxygenation of IV-22-Z (C^Df, rde-acetone

= 5:1,400 MHz)

The photooxygenation of the E-isomer of the TPP-ethyl butyrate complex IV-21-E, however, gave predominantly "ene" products. The results are summarized in Table 4.4. The photooxygenation of IV-21-E in CDCI3, CDCI3 with 20% MeOD, and de-acetone were completed promptly within 3 minutes (entries 2 to 4). The photooxygenation in C^De on a larger scale (6 times more concentrated, in order to isolate photooxygenation products) took

30 minutes to finish (entry 1). The [2+2] cycloaddition mode competed ineffectively against

the "ene" reaction regardless of solvent. Both the Z- and E-diastereomers of the

hydroperoxides IV-34 were observed, and the Z-isomer slightly outweighed the E-isomer,

presumably due to the lower steric repulsion in the former configuration. The Z/E assignment

was achieved by a field-effect analysis of the NMR spectrum of a mixture of diastereomers

(vide infra).

Table 4.4 Photooxygenation of IV-21 -E

IV-32-E ^ IV-34-Z E Ë IV-21-E

TPP O p2 F4 -QpZ, IV-34-e F'""^ IV-30

Y 2+2 cydoaddhion "ene" reaction

Conc 1 Time j Conv i [2+2] t "ene"(%) Ester (%), Entry' Solvent 1 [2+2]: "ene' (mM) i (inin) i (%)' ! (%)' ^ (Z:E) (byGC)^ U 730" 1 >95 1'24^"'""" 155 (62^Sr -^^jQ- CDCI3 - 2 - -;"1 !>95"~ 'l6(5lT49) 28:62 CDCU: MeOD=4: 2 1.5 1 >95 39 61 (51:49) ' 39:61 26 1 1 1 1 d^-acetone ""'2^• '^'"""2^5" r >95 ^""72(58:421 '[ 20:80^ "^30 " All the experiments were carried out at room temperature and molar ratios of the substrate (based on A ) to the internal standard (based on the aromatic proton), conversions, and yields (based on 100% conversion) were determined by 'H NMR spectroscopy. * Conversions based on A*. ' Combined yields of the dioxetane IV-32-E and the cleavage products (IV-30 or ester). Combined yields of IV-34-Z and IV-34-E, the Z/E ratio was determined by NMR. ''Determined by GC peak area ratio and calculated using Equation 3.2, F= 0.78.

In the stepwise NMR spectra (Figure 4.9) of the photo irradiation of IV-21-E in C(,D(,

(entry 1, Table 4.4), it is obvious that the two proton signal sets (a singlet at 5.56 ppm with a triplet at 4.51 ppm and a singlet at 5.25 ppm with a triplet at 5.40 ppm) gradually increase

during the photoirradiation. These are characteristic peaks of the hydroperoxide IV-34-Z/E.

Based on the field effect analysis (Figure 4.10), the former set of signals was readily assigned

to the Z-isomer, while the latter was assigned to the E-isomer, considering the F* proton is

affected by the relatively close enol ether oxygen to shift downfield and the F^ proton is

affected by the ethyl group from the same side of the double bond and thus shifts sliglitly upfield. Dioxetane was barely observed, if at all, and it likely decomposed instantly to give

IV-30 and ethyl butyrate as indicated in the specfra.

* unidentified product IS IS

c6 :8F 30 mins

10 mins III' 11 S mins

I

1.5 mins

0.5 min

0 min

9,0 8,0 7,0 6,0 5,0 4.0 3,0 2.C 1,C ppm(t1)

Figure 4.9 'H NMR spectral sequence of the photooxygenation of IV-21 -E (C^De, 400 MHz) Figure 4.10 Field-effect analysis of IV-34-E

The 'H NMR sequential spectra of the photooxygenation of IV-21-E in other solvents (entries 2 to 4) are illustrated in Figure 4.11. Similar peak sets corresponding to the characteristic hydroperoxide protons (E^/E^ and F^/F^) are observed in all cases, hi addition, dioxetane was preserved in all these reactions, as a characteristic singlet appears at 5.87 ppm

(in CDCI3, entry 2), 5.72 ppm (in CDCI3 with 20% MeOD, entry 3) or 6.11 ppm (m de- acetone, entry 4).

Attempts were made to isolate the hydroperoxide IV-34-Z/E. The crude reaction mixture from entry 1 was concenfrated and chromatographed on a silica gel preparative TLC plate using 1% MeOH in CH2CI2 as eluant. Although the hydroperoxides can be separated from the [2+2] cycloaddition products, the Z/E isomers co-developed and decomposed slightly during the chromatography. The 'H NMR and COSY spectra of this partially purified hydroperoxide mixture in de-acetone are shown in Figure 4.11 and Figure 4.12. The COSY spectrum confirmed our assignments of triplets at 4.51 ppm and 5.40 ppm to protons E^ and

F of the hydroperoxides as they correlate to the neighbouring methylene protons and the latter in turn correlate to the methyl protons. 1 min, entry 2 In CDCI3

0 min, entry 2 in CDCI3

IS

1.5 mins, entry 3 —v.. I • * in CDCI3 (with 20% MeOD)

0 min, entry 3 in CDCI3 (with 20% MeOD)

(x other impurities] E6 p8 "ene" products 11 from the entry 1 IJiv '1 after PTLC and dissolved in D-acetone IS

\ lî i \ Ml, ., JJV\J 1.5 mins, entry 4 _V ^ 1 V ' in D-acetone

J L 0 min, entry 4 in D-acetone 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.C 1.0 ppm (f1)

Figure 4.11 H NMR spectral sequence of the photooxygenation of IV-21 -E in various solvents (400 MHz) Figure 4.12 COSY spectrum of the partially purified hydroperoxide mixture (de-acetone, 400

MHz, entry 1, Table 4.4) 4.4.2 Interpretation of Different Beliaviors Observed in the Photooxygenation of the

First and Second Generation Complexes—the Cis-Directing Effect.

The remarkable chemoselectivity differences observed in the photooxygenation of

the Z- and E- isomers of IV-21 and other second generation photosensitizer-drug complexes

(see following sections 4.4.3 and 4.4.4), as well as the absolute regioselectivity of the "ene" reaction in the photooxygenation of the first generation complexes reported in Chapter Three, can be explained by the cis-directing effect, a phenomenon where singlet oxygen is directed predominantly or exclusively to one side of the double bond having a directing group in singlet oxygenation reactions.'^^''^'''"^'^

Typical examples^'^'^'^'^'^ of the cis-directing effect are presented in Scheme 4.13.

For trisubstituted aliphatic olefins, the "ene" reaction occurred predominantly on the di• substituted side of the double bond (reactions A, B and C). Alkoxy groups provide a stronger directing effect than alkyl groups, as indicated by the fact that H-abstraction of the sterically hindered cyclopropyl group occurred when it is cis to a methoxy group, but did not when it is cis to a methyl group (reactions C, D and E). In addition to alkyl and alkoxy groups, a phenyl group also shows a directing effect, as exemplified by the reaction I. 70% of the H-abstraction took place on the same side of the double bond as the phenyl group in contrast to 30%) on the opposite side. 1,4-Cycloaddition failed to compete with the "ene" reaction as no endoperoxide was observed in this reaction. A comparison of reactions G and I indicates the phenyl group is less effective than the alkoxy group in terms of directing the attack of singlet oxygen. In the absence of an allylic hydrogen on the disubstituted side of a cw-/3-methoxy styrene (reactions

H and K), 1,4-cycloaddition occurred exclusively, even with the presence of an allylic hydrogen on the opposite side of the double bond.

Et. Et A: hv, O2, sens Et, OOH OOH HOO A (520/0) . ^ (48%) (0%) Ref. 29

D3C, hv, O;, sens D3C, DgC^ pOH D2C OOH B: D-acetone HOO-;^-^ (53%) + (40%) + (70/^) Ref. 29

hv, O2, sens OOH OOH C: \ D-acetone HOO ^ (85%) + J~\^ (0%) (15%) Ref. 29

< < <} hv, O2, sens OOH OOH D: y=x CeHg (72%) (28%) Ref. 27 ^ OMe OMe

hv, O2, sens E: M CsHe (100%) Ref. 27 OMe OMe

hv, O2, sens OOH F: CeHg (100%) Ref. 27 OMe > OMe

hv, O2, sens OOH —^ (OO H G: /=\ D-acetone y-\ (86%) + J—( (14%) OMe Ref. 29 OMe OMe

hv, O2, sens OMe <] OMe H: /=\ Ph OMe ^^nCfiHec (100%) Ref. 27 o -OH

Ph / hv, O2, sens Ph Ph, OOH Ph OOH HOO D-acetone -^(70%) (20%) + (10%) Ref. 29

__pMe hv,02, sens OMe J: Freon 11 (>90%) Ref. 31 Ph Ph OOH

hv, O2, sens OMe K: Freon 11 (>90%) Ref. 31 Ph OMe ^ ^O

Scheme 4.13 Examples of the cis-directing effect The cis-directing effects of alkoxy groups, alkyl (bearing at least one hydrogen atom)

groups and the phenyl group are explained by Fukui's groupe''' and Stephenson^'* based on

frontier-orbital interactions. Due to the strong electrophilic character of singlet oxygen, the

interaction between the LUMO of the incoming singlet oxygen and the HOMO of the olefin

should predominate over the opposite way (i.e. a LUMO-olefin, HOMO-oxygen interaction).

As discussed in Chapter One, the perepoxide has been well accepted as the reaction

intermediate of the "ene" reaction. It has also been suggested as the intermediate or the precursor to the zwitterion intermediate of the [2+2] cycloaddition reaction. The presence of the directing groups enhance the HOMO-LUMO interaction between the singlet oxygen and the olefin substrate. As illustrated by Scheme 4.14, while the orbital of the head oxygen overlaps the T-orbital of the olefin, the lone pair (non-bonding) orbital of the alkoxy oxygen, the C-H bonding orbital of the alkyl group or the 7r-orbital of the phenyl group interacts with the orbital of the tail oxygen in the favorable phase relation, which stabilizes the transition state leading to the perepoxide formation and consequently anchors the tail oxygen to the side of the double bond with the directing group. The relatively strong directing effect of the alkoxy group can be attributed to the fact that the higher lying n-orbital interacts more effectively with the 7r*-antibonding orbital of the incoming singlet oxygen.^'* +

Alkoxy Directing Effect -CH Directing Effect Phenyl Directing Effect

Scheme 4.14 HOMO-LUMO interactions for the cis-directing effect

It is straightforward to interpret our photooxygenation results of the first and second generation photosensitizer-drug complexes in this view (Scheme 4.15). For the first generation complexes, the directing effect of the combination of an alkoxy group and an alkyl group on one side of the alkene should completely outweigh the directing effect of the alkyl group on the mono-substituted side. As a result, the incoming singlet oxygen was directed to the disubstituted side. Additionally, the H-abstraction on the mono-substituted side of the double bond lacks the stabilization of the transition state by the anomeric effect,^which is present in the other route. Therefore, in addition to the [2+2] products (minor), an absolutely regioselective "ene' product was predominantly generated in the photooxygenation of the first generation complexes. Our results also indicate that a perepoxide intermediate is irreversibly formed and does not undergo pyramidal inversion before the hydrogen abstraction (the "ene" reaction) or the cycloaddition. First-generation Second-generation Complex Complex A A r

Sens -v^O Sens-^^O T 3 T R2 OR1 o R10' R, o R2 OR1 (Z-isomer) (Znsomer) (E-isomer)

R2- OR1 -OR1 Ri \2+2 I "ene" ene 2+2 \2+2 / minor \ "ene" 2+2 I product/ -, (not observed) , ^-.^ V / minor \ ( St) ( P^*-»-*) H o- ?ï~ORi or '^2

/•H

R2 ^OR,

/Anomeric Effect \ / No Anomeric Effect \ I Stablization r \ Stablization j

Hi -0^0

OR1 R1O R2 OR1 / onV ^ major ^ (not oljserved) product V product/

Scheme 4.15 Interpretation of the photooxygenation results by the cis-directing effect

For the photooxygenation of the Z-isomers of the second generation complexes

bearing enediol linkages, the directing effect of dual alkoxy groups on the same side of the

double bond should completely outweigh that of the mono-alkyl group on the other side. As a result, quantitative yields of the [2+2] cycloaddition products were observed, due to the

absence of the allylic hydrogen on the disubstituted side of the double bond. For the E-

isomers, the strongly directing alkoxy group appears on both sides of the double bond.

Therefore, despite the majority of the incoming singlet oxygen was directed to the di•

substituted side, which led to the predominant "ene" reaction products, a small percentage of

singlet oxygenation still occurred on the mono-substituted side and gave the [2+2]

cycloaddition products.

In the photooxygenation of IV-29-Z/E bearing /3-amino enol ether linkages, the

exclusive [2+2] cycloaddition selectivity was observed for both Z- and E- isomers (see the

following section 4.4.3). This is attributed to the exceptionally high activation effect of the

amino group towards the [2+2] cycloaddition reaction as discussed in section 4.1. Several

examples in Scheme 4.2 show the exclusive generation of the [2+2] cycloaddition products even with the presence of an allylic hydrogen at the same side of the double bond as the amino group.

4.4.3 Photooxygenation of Other Second Generation Photosensitizer-Drug Complexes

(Z-isomers)

The results of photooxygenation of IV-23-Z to IV-29-Z at room temperature are summarized in Table 4.5. C^D^ was employed as the solvent for most of the reactions due to its availability and acid-free nature. An absolute chemoselectivity of the [2+2] cycloaddition was observed in all reactions owing to the powerful cis-directing effects from the two hetero- substituents. Another remarkable aspect is the high efficiency: all the photooxygenation finished within the time span from 2 minutes to 7 minutes in concentrations ranging from 6 mM to 15 mM. The partition of the [2+2] cycloaddition products between dioxetanes and their cleavage products immediately after the photooxygenation is substrate-dependent.

Dioxetane cleavage products predominated the photooxygenation of naproxen-incorporated complexes (entries 6 and 7). Furthermore, in the photooxygenation of amide-incorporated complexes (entry 3), dioxetanes completely decomposed at all stages of the reaction, presumably due to the catalytic effect of the amino group for dioxetane cleavage. Indeed, dioxetanes are so susceptible that in addition to thermolysis, their cleavage can be catalyzed by amines and trace metal ions such as Cu^"^, Ni^"^, Co^"^, Zn^'^, etc.'*^ Since these "catalysts" are ubiquitous in human tissue, it is reasonable to assume that the m vivo photooxygenation of the new generation complexes (Z-isomers) will instantly lead to the quantitative release of the incorporated drugs. Table 4.5 Photooxygenation of IV-23-Z to IV-29-Z

sens o ^ ^ Og' sens o^:::î'~~^:r^o^o R,Y , R2 02 YR, YR,

IV-30 (Sens = TPP) IV.35-Zto IV-41-Z IV-31 (Sens = BPD)

V , , J Y Dtoxetane Dioxetane Cleavage Products sens = Ph-

Ph (TPP-based) P S ~° IV-23-Z IV-24-Z (Y = O,M (BPD-based) IV-25-Z rV-27-Z IV-29-Z IV-26-Z(±) IV-28-Z(±) total Gone Time Conv Diox Cleav Ester (%), Entry' Complex [2+2] (mM) (min) (%)* (%)' (%)' (by GC) ^

IV-35- >95 Z 36 >95 1.20 72

tV-23.Z (64) IV-36- 10 >95 Z 59 94 0.43 90 (35) IV-37- 3' >95 Z/E >95 >95 2.06 (0) IV-38- 15 2.5 >95 Z 23 92 1.55 >95

Ni5-Z (69)^ IV-39- 95 Z 9 94 1.55 >95

IV-26-Z i \ (85)^' IV-40- >95 Z 76 2.31 66

IV-27-Z i (12)^^ IV-41- >95 Z 70 >95 2.31 57 (27)^- " All the experiments were carried out in C^D^ at room temperature unless otherwise mentioned. Molar ratios of the substrate (based on A*) to the internal standard (based on the aromatic proton), conversions and yields (based on 100% conversion) were determined by 'H NMR spectroscopy. * Conversions based on A*. " Labels of dioxetanes are shown with yields in parentheses based on B*". Yields of the cleavage products. Total yields of the [2+2] cycloaddition, the sum of the dioxetane yields and the cleavage product yields. ^ Determined using Equation 3.1. •^Determined by GC peak area ratios and calculated using Equation 3.2. * In d,5-acetone. 'A Z/E = 4:1 mixture was used as starting materials. ^ Mixture of diastereomers. All the photooxygenation processes were monitored by NMR and GC on a step-by-

step basis. The sequential spectra of the photooxygenation of IV-23-Z (entry 1) and IV-24-Z

(entry 2) are straightforward as the gradual decrease of the olefinic proton signals are

accompanied by the increase of the signals from dioxetanes and cleavage products (see

Figure 4.13 and Figure 4.14 at the end of this chapter). Interestingly, in the photooxygenation

of a Z:E = 4:1 mixture of the amide-incorporated complex IV-29 (entry 3), both isomers gave

exclusively dioxetane-cleavage products, with the Z-isomer reacting much faster than the E-

isomer. In the stepwise 'H NMR spectra (Scheme 4.16), the signals of the E-isomer (E-A** and

E-A'^) remained mainly unchanged while those of the Z-isomer (Z-A** and Z-A"*) rapidly

decreased within the first 1.5 minutes. After 5 minutes irradiation, signals from both isomers

totally disappeared in exchange for the signals of IV-30 and the released amide. The complete

conversion of the E-isomer to the dioxetane cleavage products is evident as no new peaks

(from endoperoxides or other possible photolysates) emerged in the 6.4 ppm to 4.4 ppm region during the 1.5 minutes to 5 minutes irradiation period when the E-isomer started to decay noticeably until it disappeared altogether. Scheme 4.16 'H NMR spectral sequence of the photooxygenation of IV-29-Z/E (CeDe, 400 MHz)

The photooxygenation of the ibuprofen-incorporated TPP-based complex IV-25-Z

(entry 4) was monitored by NMR as shown in Scheme 4.17. The resulting dioxetanes should contain four diastereomers as two pairs of enantiomers. This is indeed observed as characteristic proton signals (B*', B'^ B'^ and B'") of the dioxetanes IV-38-Z-XA' appear as a series of peak pairs and each pair consists of two peaks at 1:1 ratio. o no A ^^TIASA^AH V R3 RCO I OSB^O 1, „I

IV-25-Z

^ c c3 c5 ^6 ^

XA'-B" IS A 18/ X/Y-B® /j f C6| ^ 2.5 mins

LLJ ^ 1 min

0 min ~î —I—I — 8,0 7.0 6.0 5.0 40 3.C 2.0 1.0 ppm (ti)

Scheme 4.17 'H NMR spectral sequence of the photooxygenation of IV-25-Z (CÔDÔ, 400 MHz)

The ibuprofen-incorporated BPD-based complex IV-26-Z should give theoretically 8 diastereomers as four pairs of enantiomers after the photooxygenation (entry 5). Due to the separation between the chiral centers on the esterifying alcohol chain and those on the BPD- backbone, each characteristic proton from the dioxetane IV-39-Z-X/Y shows only a pair of peaks at 1:1 ratio (Scheme 4,18). X

IV-26-Z

D10

fi JS)^

IS XA'-B^''

j . l", Il is t V> "...

, 3 mins

,1. i! J'.AJ' ^ 1 min

'"•^ 0 min

10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.C 1.C ppm (tl)

Scheme 4.18 'H NMR spectral sequence of the photooxygenation of IV-26-Z (CeDe, 400 MHz)

The photooxygenation of the naproxen-incorporated complexes IV-27-Z (TPP-based) and IV-28-Z (BPD-based) gave similar results except that the majority of dioxetanes decomposed during the irradiation to release the naproxen methyl ester. The step-by-step 'H

NMR sequential spectra are presented in Figure 4.15 and Figure 4.16 at the end of this chapter. 4.4.4 Photooxygenation of Other Second Generation Photosensitizer-Drug Complexes

(E-isomers)

A moderate to high "ene" chemoselectivity was observed in the photooxygenation of

the E-isomers of some second generation complexes as illustrated in Table 4.6. Moreover, all

three "ene" reactions are stereoselective as Z-products formed predominantly. For the lactone-

incorporated substrate IV-24-E, the Z-product is the only possibility regarding the cyclic

structure (entry 1). For the ibuprofen-incorporated IV-25-E and IV-26-E (entries 2 and 3), the

Z-selectivity of the "ene" reactions is the result of the steric repulsions between the

substituents on the newly formed double bond. Dioxetanes, as possible by-products, were

difficult to be clearly identified in the NMR spectra of the photooxygenation and the GC yields were used to show the overall yields of the [2+2] cycloaddition. As pointed out in section 1.2, the allylic hydrogen needs to attain the proper alignment (perpendicular to the olefin plane) before the H-abstraction could occur in the "ene' reaction. For c^branched substrates such as IV-25-E and IV-26-E, it would require a sterically unfavorable 1,3-allylic strain for such a conformational alignment. It is therefore remarkable that the "ene" reaction mode still overweighed the [2+2] cycloaddition mode in the photooxygenation of these substrates. Table 4.6 Photooxygenation of IV-24-E, IV-25-E, and IV-26-E

hv (> 540nm) sens 02 R2 c' c* B° R2' IV-42-Z IV-30 (Sens = TPP) Starting Connplexes: IV-43-Z IV-31 (Sens = BPD) Ph IV-44-Z / Y V 2+2 products "ene" prcxiuct

O'p ^-o

(BPD-based) IV-26-a±)

Conc Time ' Conv * "ene" prod i Entry" Complex Ester (%X I r2+21-"ene"' (mM) : (mins) ! (%) * ! (yield in %)" (byGC)'' I

IV-42-Z 1.5 1 >95 I 5:95-' (86)

1V-43-Z 11 14 >95 30 33:67' (61)

IV-44-Z 1.5 >95 33 35:65' (60) '

IV-2B-E " All the experiments were carried out in C^Dé at room temperature unless otherwise mentioned. Molar ratios of the substrate (based on A*) to the internal standard (based on the aromatic proton), conversions and yields (based on 100% conversion) were deten-nined by 'H NMR spectroscopy. * Conversions based on A*. " Z-isomers of the hydroperoxides dominate in all cases and yields are regarding the Z-isomers only. Determined by GC peak area ratios and calculated using Equation 3.2. " Calculated based on GC yields of the [2+2] cycloaddition products and NMR yields of "ene" reaction products. ^ F= 0.43. ^ Photooxygenation was carried out at 5°C. F= 1.55. 'Mixture of diastereomers.

The H NMR spectra of the photooxygenation of IV-24-E and IV-26-E at room

temperature are shown in Scheme 4.19. It took only 1.5 minutes for each reaction to complete.

For the entry 3 photooxygenation, it is of note that the two pairs of enantiomers of the

hydroperoxide products IV-44-Z-XA' can be marginally distinguished by some characteristic

peak pairs (at 1:1 ratio) in the NMR spectrum. Entry 1 ÎPP O'^^rV^O'^"^" ^°"'^>. TPP^O-^P^cTY^ ^° * [2+2] products IV-24-E IV-42-Z O OOH iB'" hv V B' DST asB^" Entry 3 BPO-^O^^^JV^Q-^ :> eOOnm) BPD'^O^'X^î^cfSfW^^" ?" * t^+a] products O2,

IV-26-E

IS IS

A« \ ^ , Mi JL_Js-_J P.O. of IV-24-E 1.5 mins, entry 1

ihrneJ^Is J^.«i.»M.wW^^^NA^ P.O. of IV-24-E 0 min, entry 1

• : signals from dioxetane presumably IS B^' IS

-OOH

,^ .1 n ,1 "1 07' \^ P.O. of IV-26-E 1.5 mins, entry 3

k P.O. of (V-26-E ^ !~ 0 min, entry 3

10,0 9,0 8,0 7,0 6,0 4.0 3,0 2.0 ppm(t1) Scheme 4.19 H NMR spectral sequence of the photooxygenation of IV-24-E and IV-26-E

(CôDe, 400 MHz)

To slow down the photooxygenation process and record the stepwise sequential spectra, the photooxygenation of IV-25-E was carried out at 5°C (entry 2). It took 14 minutes to complete and the spectra are presented in Scheme 4.20. Despite the fact that the proton signals of and partially overlap, the consumption of the substrate and the generation of the major "ene" product can be readily monitored based on the characteristic peaks of A^ and

B'^. The release of the incorporated ibuprofen ester is evident by the increase of the D" signal. IV-25-E IV-43-Z

DCM B" IS

mins

AA.. J ill 8 mins

.^A^AdiUi^'^^. ,

._Jii/L LlLl I 1 1 J J_, __j'>Vx.,._._^.AJ._ 0 min

9.0 7.0 6.0 5.0 4.0 3.C 2.0 1.C ppm (t1)

Scheme 4.20 'H NMR spectral sequence of the photooxygenation of IV-25-E (CeDe, 400 MHz)

4.5 Summary

Two strategies have been proposed to build the new generation photosensitizer-drug complexes which can release the incorporated drugs in a much improved yield over the previous generation upon visible light irradiation. Although the strategy of connecting a drug molecule with a photosensitizer through an enamine linkage failed to come to fruition, the second generation linker molecule IV-7 facilitated the swift assembly of the desired complex by the Takeda alkoxymethylenation and the Steglich esterification. Using this methodology. drug molecules can be incorporated through enediol ether or /3-amino enol ether linkages,

generating final complexes with Z- and E-stereoisomers. Despite the fact that the

chemoselectivity of the [2+2] cycloaddition in the photooxygenation of most E-isomer

complexes was unexpectedly low, a complete [2+2] cycloaddition selectivity was achieved in

the photooxygenation of the Z-isomer complexes. Such reactivity differences can be readily

explained by the cis-directing effects of the olefin substituents of the diastereomers.

Aliphatic and aromatic esters, lactones and amides have been successfially

incorporated and quantitatively (or near quantitatively) released using this strategy. In particular, complexes with the Visudyne® analogue as the photosensitizer moiety and the ibuprofen or naproxen derivatives as the drug moiety have been synthesized. Upon visible light irradiation, methyl esters of ibuprofen and naproxen have been promptly released in quantitative yields. The next stage of the development of our photodynamic drug delivery system should

involve the in vitro or even the in vivo evaluation of the drug-releasing efficiency of the photosensitizer-drug complexes upon photoirradiation. Accordingly, the structure and the linking strategy of the complexes can be further optimized by adopting different photosensitizers as well as by using new linker molecules with various chain lengths or additional structural features to bring about the desired pharmacokinetic profile and ultimately the biological efficacy. IS IS

J Aa.

JuMwVJ

A_JUL n I i I ^ I i i— —^—1—r \ T r 9.0 8.0 7.0 6.0 5.0 4.0 3.0 ppm (t1) 2.C 1.0 1.0C

< 1.5C

2.0C

^ 2.5C

3.0C

3.5C

i soi 4.0C i

4.5C . ppm (t1

4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.0C ppm (t2) from from from CDCI3 IS MeOD IS MeOD

ii w 3 mins

UJU Ku 1 min

kJl JJ ^ 0 min T—I—I—I—\—i—j—r j \ I I I ^ I i I I j I 1 1 i I I I I I ^—I—\—\—I—^—i—1—!—r 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.C ppm(f1)

Figure 4.5 'H NMR spectral sequence of the photooxygenation of IV-21 -Z (CDClsiMeOD = 4:1, 400 MHz) 8 mins

5 mins

1 min

0 min

Figure 4.6 'H NMR spectral sequence of the photooxygenation of 17-21-2 (d,-acetone, 400 MHz) 60 mins

8 mins

5 mins

Omin IS

j i i I—I—^— 5.0 4.0 3.0 2.C

Figure 4.13 NMR spectral sequence of the photooxygenation of IV-23-Z (C6D6, 400 MHz) IS IS

B6

2 mins

^^^^ ,

0 min

H NMR spectral sequence of the photooxygenation of IV-24.Z (de-acetone 400 MHz) IS Ester for C5 comparison

I

mins

B6

lu 'Ai 3 mins

1 min

LI 0 min 7.0 6.0 5.0 4.0 3.C 2.0 o 00 ,—I

il Ester for comparison

IS IS

/I ? V \ 3 mins

LA 1 min

Jul 1 i Ah 0 min "~~| ^ ^ 1 1 1—1 ! \ 1 j— 10.0 9.0 8.0 7.0 6.0 5,C 4.0 3.C 2.C 1.0 ppm (ti)

Figure 4.16 'H NMR spectral sequence of the photooxygenation of IV-28-Z (CeDa, 400 MHz) CHAPTER FIVE

Experimental 5.1 Instrumentation and General Materials

The NMR spectra were recorded on a Bruker WH-400, a Bruker AV-300 or a Bruker

AV-400 in the solvents indicated and were referenced to residual solvent peaks. For a mixture

sample, such as photooxygenation crude mixtures in Chapter Three and Four, 2D NMR

spectra ('H-'H COSY, 'H-'^C HMQC or 'H-'^C HMBC) were usually acquired to assist the peak assignments (or peak extractions) of the 'H- or '^C NMR spectrum. Low and high resolution mass spectra were determined on a Micromass LCT TOF-ESI mass spectrometer or a KRATOS Concept IIHQ hybrid mass spectrometer, with only molecular ions (M"^, [M+H]"",

[M+Na]"*") being reported. High resolution ESI mass spectrometry (HRESIMS) measurements are valid to ± 5 ppm. Elemental analyses were performed on a Carlo Erba Elemental Analyzer

1108. As for moisture-sensitive, light-sensitive, or hard-to-combust compounds, HRMS was usually resorted to when combustion analysis failed to give acceptable results. The UV-Vis spectra were recorded on a Varian Cary-50 spectrophotometer. X-ray crystallographic data were collected on a Rigaku/ADSC CCD. Gas chromatography (GC) was carried out on a HP

5890 instrument with a 25 m x 0.32 mm HP-17 column, packed with 50% phenyl and 50% methyl siloxane. A flame ionization detector (FID) was employed in conjunction with a HP

3390A digital integrator and He was used as carrier gas. Photoirradiations of the photosensitizer-drug complexes were carried out with a 250 W Osram HLX 64655 arc lamp in an Oriel lamp housing (model 66184) and the light output passed through a K2Cr207 aq. fiher solution (0.2 M) or a Corion P70-650-S filter.

AH chemicals for syntheses were purchased from Sigma-Aldrich fine chemicals,

Acros Chemicals, or Fisher Scientific. If necessary, chemicals were purified by published procedures.^^° Ring B-BPD-7^-monoacid 111-23 was obtained from QLT Inc.. Deuterated

solvents for NMR measurements were purchased from Cambridge Isotope Laboratories or

Aldrich. Flash chromatography was performed on silica gel (Silicycle or BDH, 70-230 / 230-

400 mesh) and basic alumina (Brockman, 60-325 mesh, deactivated with 3% water to activity

II or 6 % water to activity III). Analytical Thin Layer Chromatography (TLC) was performed on aluminium backed plates pre-coated with silica (Merck or Aldrich, 0.2 mm, 60 mesh with

F254 indicator) or alumina (Merck, 0.2 mm, activity III, 60 mesh with F254 indicator). Prep.

TLC was performed on glass backed plates pre-coated with silica (Merck, 0.5 mm and 1 mm,

60 mesh without indicator).

5.2 Experimental Data for Chapter Two

Dipyrromethane 11-11

Using a modified literature procedure,'" a suspension of paraformaldehyde (1.73 g,

57.7 mmol) in pyrrole (100 mL, 1.44 mol) was heated to 50 °C before the addition of TFA

(444 fjL, 5.77 mmol). The solution was stirred for 5 min under Ni. The excess pyrrole was removed under reduced pressure and the resulting crude mixture was purified by silica gel chromatography (CH2Cl2:hexane = 1:1 as eluant) to give 11-11 (4.0 g, 48% yield).

R/(sihca-CH2Cl2:hexane = 2:1): 0.23; 'H-NMR (300 MHz, CDCI3): ô = 7.90 (br. s,

2H), 6.60 (m, 2H), 6.13 (q, 2H, J = 2.8 Hz), 6.02 (m, 2H), 3.98 (s, 2H). These data agree with the literature data." ' 5-Phenyldipyrromethane 11-12

According to the general procedure described for 11-11 using benzaldehyde (4.42 mL,

44.3mmol) and running at r. t., silica gel chromatography (CH2Cl2:hexane = 2:1 as eluant) of

the crude reaction mixture gave 11-12 (4.2 g, 43% yield).

R/(sihca-CH2Cl2): 0.40; 'H-NMR (300 MHz, CDCI3): ô == 7.88 (br. s, 2H), 7.30-7.18

(m, 5H), 6.68 (m, 2H), 6.14 (m, 2H), 5.91 (m, 2H), 5.46 (s, IH). These data agree with the

literature data. ' ' '

5,15-Diphenylporphyrm 11-1

Using a modified Hterature procedure,"^ to a degassed CH2CI2 solution (1 L) of benzaldehyde (1.02 mL, 10 mmol) and dipyrromethane 11-11 (1.5 g, 10 mmol) was added

TFA (0.77 mL, 10 mmol) dropwise. The solution was stirred for 3 h protected from the light before DDQ (1.7 g, 7.5 mmol) was added. The mixture was then stirred for another 3 h open to air before passing through a basic alumina column to remove polymeric byproducts. The resulting crude solution was concentrated and pre-adsorbed onto silica gel for dry-loaded chromatography (silica, CH2Cl2:hexane = 2:1 as eluant) to give 11-1(1.0 g, 44% yield).

R/(silica-CH2Cl2:Hexane = 1:1): 0.43; 'H-NMR (400 MHz, CDCI3): ô = 10.31 (s,

2H), 9.39 (d, 4H, J - 4.6 Hz), 9.07 (d, 4H, J = 4.6 Hz), 8.28-8.25 (m, 4H), 7.81-7.78 (m, 6H),

-3.13 (s, 2H); LSIMS (m/e): 463 ([M+H]^); UV-Vis (CH2CI2) Wmn: 404, 502, 536, 576,

630. These data agree with the literature data.'

5,10,15-Triphenylporphyrin 11-13

According to the general procedure described for 11-1 using paraformaldehyde (0.3 g. 10 mmol) and 5-phenyldipyrromethane 11-12 (2.22 g, 10 mmol), a mixture of 5,10,15-

triphenylporphyrin 11-13 and 5,10,15,20-tetraphenylporphyrin (TPP) 11-14 was produced

(0.28 g, 11-13:11-14 =1:2, 10% combined yield).

'H-NMR (400 MHz, CDCI3, peaks were extracted from the spectrum of 11-13 and II-

14 mixture): ô = 10.21 (s, IH), 9.33 (d, 2H, J = 4.7 Hz), 9.00 (d, 2H, J = 4.6 Hz), 8.88 (d, 2H,

J - 4.8 Hz), 8.85 (d, 2H, J = 4.8 Hz), 8.24-8.21 (m, 6H), 7.71-7.67 (m, 9H), -3.02 (s, 2H).

These data agree with the literature data.^^'

5,10,15,20-Tetraphenylporphyrin 11-14

'H-NMR (400 MHz, CDCI3, peaks were extracted from the spectrum of 11-13 and II-

14 mixture): ô = 8.82 (s, 8H), 8.21-8.18 (m, 8H), 7.79-7.72 (m, 12H), -2.79 (s, 2H). These data agree with the literature data.^^^

10-Iodo-5,1 S-diphenylporphyrin 11-2

Following the literature procedure, diphenylporphyrin 11-1 (100 mg, 0.22 mmol) and (F3CC02)2PhI (66 mg, 0.15 mmol) were dissolved in 100 mL CHCI3. To this stirred solution was added a CHCI3 solution (8.2 mL) of I2 (76.2 mg, 0.3 mmol) dropwise. The solution was then stirred under N2 for 3 h before it was washed with aq. sodium sulfite solution, water, and brine, and dried over sodium sulfate. After solvent evaporation, the residue was recrystallized with CH2Cl2/Hexane to remove diiodide byproducts and the filtrate was concentrated and pre-adsorbed onto silica gel for dry-loaded chromatography (silica,

CH2Cl2:hexane ==:1 as eluant) to furnish 11-2 (50 mg, 40% yield).

R/(silica-CH2Cl2:hexane = 1:1): 0.55; 'H-NMR (300 MHz, CDCI3): ô = 10.17 (s,

IH), 9.74 (d, 2H, J = 4.9 Hz), 9.28 (d, 2H, J = 4.6 Hz), 8.94 (d, 2H, J = 4.7 Hz), 8.90 (d, 2H, J

= 5.0 Hz), 8.21-8.18 (m, 4H), 7.80-7.73 (m, 6H), -3.02 (s, 2H); ESIMS (m/e): 589 ([M+H]^;

UV-Vis (CH2CI2) >smx/nm: 414, 512, 546, 588, 644. These data agree with the literature

10-Iodo-5,15-diphenylporphyrinato zmc(II) ll-2-Zn

Following the hterature procedure,'^^'^ to a CHCI3 solution (50 mL) of lO-iodo-5,15- diphenylporphyrin 11-2 (50 mg, 0.085 mmol) was added a methanol solution (2 mL) of zinc acetate dehydrate (50 mg, 0.23 mmol). The solution was stirred overnight before it was washed with water and brine and dried over sodium sulfate. After solvent evaporation, the residue was recrystallized with CH2Cl2/hexane to fiimish 11-2-Zn quantitatively.

R/(silica-CH2Cl2): 0.73; 'H-NMR (400 MHz, CDCI3): ô = 10.22 (s, IH), 9.83 (d, 2H,

J = 4.7Hz), 9.35 (d, 2H, J - 4.5 Hz), 9.02 (d, 2H, J = 4.5 Hz), 8.99 (d, 2H, J = 4.7 Hz), 8.21-

8.18 (m, 4H), 7.80-7.74 (m, 6H); LSMS (m/e): 650 ([Mf ); UV-Vis (CH2CI2) Wnm: 418,

548. These data are consistent with the literature data^^^ A CH2CI2 solution (1 L) of dipyrromethane 11-11 (0.2 g, 1.34 mmol), 4-

iodobenzaldehyde (0.15 g, 0.67 mmol) and 3,4,5-trimethoxybenzaldehyde (0.13 g, 0.67 mmol)

was stirred at 0 "C for 15 min before the addition of BF3.Et20 (17 jitL, 0.13 mmol) dropwise.

Stirring was continued for 8 h at 0 °C and 7 h at r. t. before the addition of DDQ (0.46 g, 1

mmol). After being stirred for another 3 h open to air, the crude reaction mixture passed

through a basic alumina column to remove polymeric byproducts and the filtrate was

concentrated and purified by sihca gel chromatography (CH2CI2 as eluant) to give 11-17 (55

mg, 12% yield).

R/(sihca-CH2Cl2): 0.44; 'H-NMR (400 MHz, CD2CI2): ô = 10.36 (s, 2H), 9.453 (d,

2H, J = 4.6 Hz), 9.448 (d, 2H, J = 4.6 Hz), 9.21 (d, 2H, J = 4.6 Hz), 9.08 (d, 2H, J = 4.6 Hz),

8.19 (d, 2H, J = 8.3 Hz), 8.03 (d, 2H, J = 8.3 Hz), 7.53 (s, 2H), 4.13 (s, 3H), 3.99 (s, 6H), -

3.18 (br. s, 2H); ESIMS (m/e): 679.2 ([M+H]*).

5-(3-Iodophenyl)-15-(3,4,5-trimethoxyphenyl)porphyrin 11-18

Following the general procedure described for 11-17 using 3-iodobenzaldehyde (1 g,

4.3 mmol), 11-18 (0.65 g, 21% yield) was prepared.

R/(silica-CH2Cl2): 0.40; 'H-NMR (400 MHz, dg-THF): ô = 10.41 (s, 2H), 9.47 (m. 4H), 9.18 (m, 2H), 9.04 (m, 2H), 8.69 (s, IH), 8.29 (d, IH, J = 6.6 Hz), 8.21 (d, IH, J = 6.6

Hz), 7.59 (m, 3H), 4.06 (s, 3H), 3.96 (s, 6H), -3.07 (s, 2H); LRESIMS (m/e): 679.2 ([M+H]*),

HRESIMS (m/e): calcd. for C35H28N4O3I ([M+H]*) 679.1206, found 679.1205; Anal, calcd.

(found) for C35H27N4O3I: C, 61.95 (62.09); H, 3.98 (4.15); N, 8.26 (8.26); UV-Vis (CH2CI2)

Wnm: 407, 502, 535, 574, 630.

1-EthoxyvinyI benzoate 11-19

Following the literature procedure,'''* to a dry toluene stirring solution (5 mL) of benzoic acid (0.41 g, 3.35 mmol) and [RuCl2(p-cymene)]2 (10 mg, 16.8 jumol) was added ethoxyacetylene (1 mL, 4.18 mmol) in 5 mL dry toluene dropwise at 0 °C. The mixture was heated to 40 °C and stirred for 15 min before the solvent was evaporated in vacuo and the residue was purified by silica gel chromatography (ethyl acetate:hexane:triethylamine =

1:10:0.1 as eluant) to give 11-19(0.52 g, 80% yield).

R/(silica-ethyl acetate:hexane:triethylamine = 1:10:0.1): 0.5; 'H-NMR (400 MHz,

CD2CI2): ô = 8.07 (m, 2H), 7.63 (m, IH), 7.49 (m, 2H), 3.96-3.91 (m, 3H), 3.88 (d, IH), 1.35

(t, 3H); ESIMS (m/e): 193.0 ([M+H]*). These data agree with the literature data.^^^

7>a«s-chloro bistriphenylphospine lG,20-diphenyIporphyrinatozinc(II)-5-yl palladium(ll) 11-21-Zn To a dry THF solution (5 mL) of 10-iodo-5,15-diphenylporphyrinato zinc(II) 11-2-Zn

(65 mg, 0.1 mmol) was added Pd(PPh3)2Cl2 (70 mg, 0.1 mmol) and triethylamine (14 ^L, 0.1

mmol). After refluxing for 16 h under Ar, the mixture was concentrated and recrystallized

with CH2Cl2/hexane to give deiodination product ll-20-Zn as precipitate. The filtrate was

concentrated and purified by silica gel chromatography (CH2CI2.'hexane = 1:1 as eluant) to

give 11-21-Zn (10 mg, 8% yield). Crystals of 11-21-Zn were obtained by solvent diffusion of

hexane into its CH2CI2 solution.

R/(silica-CH2Cl2): 0.41, R/(silica-THF:hexane = 1:1): 0.48; 'H NMR (400 MHz,

CD2CI2): ô = 9.95 (m, IH), 9.83 (d, 2H, J = 4.5 Hz), 9.23 (d, 2H, J = 4.6 Hz), 8.92 (d, 2H, J -

4.6 Hz), 8.50 (d, 2H, J = 4.4 Hz), 8.13-8.11 (m, 4H), 7.75-7.72 (m, 6H), 7.23-7.18 (m, 12H),

6.48-6.42 (m, 18H); ^'PNMR (161.8 MHz, CD2CI2): ô = 24.5(s); ESMS (m/e): 1190.1 (M)^

1154.9 (M-C1)^ 893.0 (M-Cl-PPha)*; UV-Vis (CH2CI2) Wnm(log e): 429 (5.25), 552 (3.86),

596 (3.51).

5,15-Diphenylporphyrinato zinc(II) ll-20-Zn

R/(silica-CH2Cl2) 0.73; 'H NMR (300 MHz, CDCI3): ô = 10.33 (s, 2H), 9.43 (d, 4H,

J = 4.5 Hz), 9.13 (d, 4H, J = 4.5 Hz), 8.26-8.21 (m, 4H), 7.80-7.72 (m, 6H). UV-Vis (CH2CI2)

?Wx/nm(log e): 407 (5.67), 536 (4.28). These data agree with the literature data.^^^ Trans-ioéo bistriphenylphospine 10,20-ciiphenylporphyrinatozinc(II)-5-yl palladium(II)

ll-22-Zn

To a DMF (5 mL) solution of 10-iodo-5,15-diphenylporphyrinato zinc(n) 11-2-Zn

(65mg, 0.1 mmol) was added Pd(PPh3)4(116 mg, 0.1 mmol). After being stirred at 110°C for

18 h, the mixture was concentrated and purified by silica gel chromatography (THF:hexane =

1:1 as eluant) to yield ll-22-Zn (85 mg, 66% yield).

R/(silica-THF:hexane =1:1): 0.45; 'H NMR (400 MHz, CD2CI2): ô = 9.96 (s, IH),

9.83 (d, 2H, J = 4.5 Hz), 9.24 (d, 2H, J = 4.5 Hz), 8.93 (d, 2H, J = 4.4 Hz), 8.55 (d, 2H, J =

4.4 Hz), 8.15-8.11 (m, 4H), 7.77-7.69 (m, 6H), 7.12-7.18 (m, 12H), 6.47-6.40 (m, 18H); ^'P

NMR (161.8 MHz, CD2CI2): ô = 23.3(s); ESIMS (m/e): 1281.6 (M*); UV-Vis (THF)

Wnm(log 6): 433 (5.22), 562 (3.99), 606 (3.78). Anal, calcd. (found) for C68H49lN4P2PdZn:

C, 63.67 (64.00); H, 3.85 (4.05); N, 4.37 (4.70).

(jF>5-(2-EthoxycarbonyIethenyl)-10,20-diphenyIporphyrinato zinc(II) ll-23-Zn

Ph

Ph

To a dry THF solution (5 mL) of tmns-chloTO bistriphenylphospine 10,20- diphenylporphyrinatozinc(II)-5-yl palladium(II) (11-21-Zn) (6.6 mg, 5.6 pmol) was added

ethyl acrylate (1.2 /iL, 11 /umol) and triethylamine (1.6 /xL, 11 ^ol). After refluxing for 1 h,

the crude mixture was concentrated and purified by silica gel chromatography (CH2CI2 as

eluant) to give ll-23-Zn (3.3 mg, quantitative yield).

R/(siHca-CH2Cl2): 0.41, R/(silica- THF:hexane = 1:1): 0.67; 'H NMR (400 MHz,

CDCI3): ô = 10.25 (d, IH, J = 15.7 Hz), 10.17 (s, IH), 9.55 (d, 2H, J - 4.7 Hz), 9.32 (d, 2H, J

= 4.5 Hz), 9.03 (d, 2H, J = 4.7 Hz), 9.01 (d, 2H, J = 4.5 Hz), 8.21-8.19 (m, 4H), 7.80-7.75 (m,

6H), 6.70 (d, IH, J = 15.7 Hz), 4.43 (q, 2H, J = 7.1 Hz), 1.48 (t, 3H, J = 7.1 Hz); LRESIMS

(m/e): 622.0 (M*); HRESIMS (m/e): calcd. for C37H26N402Zn (M*) 622.1347, found

622.1344; UV-Vis (CH2CI2) >Wx/nm(log e): 422 (5.49), 551 (4.27), 592 (3.99).

5.3 Experimental Data for Chapter Three

5.3.1 Synthesis

(3-Chloropropoxy)triisopropyIsilane III-13

Using a modified literature procedure,'^*' a DMF solurion (4 mL) of imidazole (2.86 g,

42 mmol), triisopropylsilyl chloride (4.28 ml, 20 mmol) was stirred for 5 min under N2 before the addition of 3-chloropropanol (1.58 g, 16.7 mmol). The solution was stirred overnight, quenched with 0.1 M HCl aq. solution, washed with water and brine, and dried over sodium sulfate. The solvent was evaporated in vacuo and the residue was purified by silica gel chromatography (CH2Cl2:hexane= 1:5 as eluant) to give 111-13 (4.18 g, quantitative yield).

R/(silica-CH2Cl2:hexane= 1:5): 0.4; 'H NMR (400 MHz, CDCI3): ô = 3.81 (t, 2H, J

= 5.8 Hz), 3.66 (t, 2H, J = 6.4 Hz), 1.95 (m, 2H), 1.05 (m, 21H); '^C['H] NMR (100 MHz,

CDCI3): ô = 59.7, 41.9, 35.7, 18.0, 11.9; CI (m/e): 251 ([M+H]*). No spectroscopic data has

been reported for this known compound.

(3-Iodopropoxy)triisopropylsiIane 111-14

(3-Chloropropoxy)triisopropylsilane 111-13 (2.78 g, 28 nmiol) and Nal (12.5 g, 84 mmol) were dissolved in 100 mL acetone and the solution was refluxed for 3 days. Precipitate

(NaCl) was removed by filtration and the filtrate was concentrated. The residue was diluted with CH2CI2 and the undissolved salts (excess Nal and remaining NaCl) were removed by filtration. Solvent evaporation gave 111-14 (9.5 g, quantitative yield).

'H NMR (400 MHz, CDCI3): ô = 3.73 (t, 2H, J = 5.6 Hz), 3.30 (t, 2H, J = 6.7 Hz),

1.99 (m, 2H), 1.05 (m, 21H); '-^C['H] NMR (100 MHz, CDCI3): ô = 62.7, 36.5, 18.0, 12.0, 3.8;

CI (m/e): 343 ([M+H]*). These data agree with the hterature data.^^^

(4,4-dibromobutoxy)triisopropylsilane III-15

Br

Br

To a stirring, dry THF solution (200 mL) of LDA (44 mL, 2 M solution in heptane/THF/ethylbenzene, 88 mmol) at -90 °C under Ar was added a THF solution (25 mL) of CH2Br2 (8 mL, 115 mmol) dropwise over 40 min and stirring was continued for another 30

min before the dropwise addition of a THF solution (45 mL) of (3-

iodoropropoxy)triisopropylsilane 111-14 (30 g, 88 mmol) over 1 h. The mixture was stirred at

-90 °C for 2 h before the temperature was slowly elevated to -30 °C and maintained for

another 2 h. The reaction mixture was quenched with 0.1 M aq. HCl solution, extracted with

hexane, washed with water and brine then dried over sodium sulfate. After solvent

evaporation in vacuo, the liquid residue was distilled (105 "C, 0.15 mmHg) to afford 111-15

(17 g, 50% yield).

R/(silica-CH2Cl2:hexane =1:1): 0.51; 'H NMR (300 MHz, CDCI3): ô = 5.79 (t, IH, J

= 6.2 Hz), 3.74 (t, 2H, J = 5.9 Hz), 2.55-2.48 (m, 2H), 1.78-1.74 (m, 2H), 1.04 (m, 21H);

'^C['H] NMR (75 MHz, CDCI3): Ô = 61.9, 46.4, 42.6, 31.2, 18.0, 11.9; CI (m/e): 387

([M+H]*); Anal, calcd. (found) for Ci3H2gBr20Si: C, 40.22 (40.62); H, 7.27 (7.36).

General Procedure for Takai Alkylidenation'^^ (GF-1)

To 25 mL dry THF was added a dry CH2CI2 solution (10 mL) of TiCL (0.88 mL,

8mmol) dropwise at 0 °C over 5 min under Ar. To this stirred solution was added TMEDA

(2.4 mL, 16 mmol) dropwise and stirring was continued for another 10 min at 0 °C. Zn (1.2 g,

18 mmol, freshly activated according to standard procedure^^') and PdCh (27.8 mg, 0.1 mmol) were then added to the system and the resulting suspension was warmed to 25 °C and stirred for another 1 h before the addition of a dry THF solution (10 mL) of (4,4- dibromobutoxy)triisopropylsilane 111-15 (1.7 g, 4.4 mmol) and the starting ester/amide (2 mmol). The reaction mixture was stirred overnight then quenched with triethylamine (2 mL) and sat. K2CO3 aq. solution (2 mL). The crude mixture was then passed through a basic alumina (activity (III)) column to remove the precipitate. The resulting solution was then concentrated and purified by basic alumina (activity (III)) chromatography.

(5-Ethoxyoct-4-enyIoxy)triisopropylsiIane 111-16

Ethyl butyrate (0.26 mL, 2 mmol) was alkylidenated following the general procedure

(GP-1). The crude mixture was chromatographed on basic alumina (activity (III), hexane as eluant) to furnish III-16-Z (0.41 g, 63% yield) and amixtiire of III-16-Z/E (0.17 g, 25% yield,

Z:E = 69:31). The combined yield for III-16-Z/E generated in this reaction was 88% with a stereoselectivity of Z:E = 91:9. rZ>Isomer 111-16-2

R/(alumina-CH2Cl2:hexane = 1:4): 0.55; 'H NMR (300 MHz, CD2CI2): ô = 4.54 (t,

IH, J = 7.2 Hz), 3.75-3.63 (m, 4H), 2.15-2.02 (m, 4H), 1.57-1.52 (m, 2H), 1.47-1.40 (m, 2H),

1.20 (t, 3H, J = 7.0 Hz), 1.07 (m, 21H), 0.90 (t, 3H, J = 7.4 Hz); '^C['H] NMR (75 MHz,

CDCI3): ô = 154.7, 110.6, 64.3, 63.9, 34.5, 34.1, 21.9, 21.0, 18.4, 15.9, 14.0, 12.6; LRESIMS

(m/e): 351.3 ([M+Na]*); HRESIMS (m/e): calcd. for Ci9H4o02NaSi ([M+Na]*) 351.2695, found 351.2700. (5-Ethoxy-5-phenylpent-4-enyIoxy)triisopropylsilane 111-17

Ethyl benzoate (0.29 mL, 2 mmol) was alkylidenated following the general procedure (GP-1). The crude mixture was chromatographed on basic alumina (activity (III),

CH2Cl2:hexane = 1:6 as eluant) to furnish III-17-Z (0.20 g, 28% yield) and a mixture of III-

17-Z/E (0.48 g, 66% yield, Z:E = 90:10). The combined yield for III-17-Z/E generated in this reaction was 94% with a stereoselectivity of Z:E = 93:7. 111-17 (0.68 g, 94% yield, Z:E =

93:7).

rZ>Isomer 111-17-7

R/(alumina-CH2Cl2:hexane = 1:4): 0.51; 'H NMR (400 MHz, CDCI3): ô = 7.43 (d,

2H, J = 8.4 Hz), 7.32-7.28 (m, 2H), 7.25 (m, IH), 5.32 (t, IH, J = 7.4 Hz), 3.73 (t, 2H, J = 6.4

Hz), 3.67 (q, 2H, J = 7 Hz); 2.34 (q, 2H, J = 7.6 Hz), 1.68-1.65 (m, 2H), 1.25 (t, 3H, J = 7.0

Hz), 1.06 (m, 21H); '^C['H] NMR (100 MHz, CDCI3): ô = 153.5, 136.6, 128.3, 127.5, 125.8,

114.9, 66.0, 63.2, 33.2, 22.2, 18.0, 15.3, 12.0; LRESIMS (m/e): 385.2 ([M+Na]*); HRESIMS

(m/e): calcd. for C22H3802NaSi ([M+Na]*) 385.2539, found 385.2522.

(Z>Triisopropyl(5-methoxy-6,6-dimethylhept-4-enyIoxy)silane 111-18

Methyl pivaloate (66 fjL, 0.5 mmol) was alkylidenated following the general procedure (GP-1). The crude mixture was chromatographed on basic alumina (activity (III), CH2Cl2:hexane - 1:4 as eluant) to furnish 111-18 (0.126 g, 77% yield, Z:E = 100:0).

R/(alumina-CH2Cl2:hexane = 1:3): 0.72; 'H NMR (400 MHz, CÔDÔ): Ô = 4.75 (t, IH,

J = 7.2 Hz), 3.67 (t, 2H, J = 6.4 Hz), 3.54 (s, 3H), 2.24 (q, 2H, J = 7.4 Hz), 1.68-1.62 (m, 2H),

1.12-1.11 (m, 30H); ''C['H] NMR (100 MHz, CeDe): ô = 166.3, 108.4, 63.7, 61.6, 37.5, 34.3,

29.0, 23.2, 18.7, 12.7; LRESIMS (m/e): 351.3 ([M+Na]*); HRESIMS (m/e): calcd. for

Ci9H4o02NaSi ([M+Na]*) 351.2695, found 351.2698; Anal, calcd. (found) for CjglLoOzSi: C,

69.45 (69.50); H, 12.27 (12.00).

General Procedure for desilylation (GP-2)

A THF suspension (15 mL) of silyl-protected alcohol (0.45 mmol), tetrabutylammonium fluoride trihydrate (0.28 g, 0.9 mmol) and 4 Â molecular sieves (5 mg) was stirred for 20 min before solvent evaporation in vacuo. The residue was purified by basic alumina (activity (III)) chromatography.

(Z>5-Ethoxy-5-phenylpent-4-en-l-ol III-20-Z

Following the general procedure (GP-2), the desilylation of fZ>(5-ethoxy-5- phenylpent-4-enyloxy) triisopropylsilane 111-17-Z (0.16 g, 0.45 mmol), followed by basic alumina chromatography (activity (III), CH2CI2 as eluant) yielded III-20-Z (90 mg, 98% yield).

R^ (aIumina-CH2Cl2): 0.14; 'H NMR (300 MHz, CD2CI2): 5 = 7.47-7.43 (m, 2H),

7.36-7.24 (m, 3H), 5.32 (t, IH, J = 7.4 Hz), 3.69 (q, 2H, J = 7.0 Hz), 3.64-3.60 (m, 2H); 2.35

(q, 2H, J = 7.4 Hz), 1.70-1.61 (m, 2H), 1.27 (t, 3H, J = 7.0 Hz); '^C['H] NMR (75 MHz, CD2CI2): ô = 154.7, 136.9, 128.9, 128.3, 126.5, 114.7, 66.7, 62.3, 32.9, 22.3, 15.7; LRESIMS

(m/e): 229.1 ([M+Na]*); HRESIMS (m/e): calcd. for CuHigOîNa ([M+Na]*) 229.1204, found

229.1194.

(Z>5-Methoxy-6,6-dimethylhept-4-en-l-ol 111-21

OH

Following the general procedure (GP-2), the desilylation of fZ>triisopropyl(5- methoxy-6,6-dimethylhept-4-enyloxy) silane 111-18 (0.113 g, 0.34 mmol), followed by basic alumina chromatography (activity (III), ethyl acetate:hexane = 1:4 as eluant) yielded 111-21

(33 mg, 66% yield).

R/(sihca- ethyl acetate:hexane = 1:2): 0.31; 'H NMR (400 MHz, CeDô): ô = 4.67 (t,

m, J = 7.2 Hz), 3.46-3.43 (m, 5H), 2.13 (q, 2H, J = 7.3 Hz), 1.52-1.44 (m, 2H), 1.09 (m, 9H);

'^C['H] NMR (100 MHz, CeDe): ô = 166.4, 108.6, 62.3, 61.8, 37.5, 33.5, 29.0, 22.7;

LRESIMS (m/e): 195.2 ([M+Na]*); HRESIMS (m/e): calcd. for C,oH2o02Na ([M+Na]*)

195.1361, found 195.1358.

5-(4-Methoxycarbonylphenyl)-10,15,20-triphenylporphyrln 111-24

Ph Following the literature procedure,^^® to a stirred degassed CHCI3 solution (800 mL)

of benzaldehyde (3.7 mL, 37 mmol), methyl 4-formylbenzoate (2.0 g, 12.3 mmol) and pyrrole

(3.1 mL, 44.5 mmol) was added BFs-OEta (0.2 mL, 1.6 mmol) dropwise. Stirring was

continued for 19 h under Ar before the addition of DDQ (5.1 g, 22.3 mmol). The mixture was

maintained at r. t. for 1 day before solvent evaporation and purification by silica gel

chromatography (CH2Cl2:hexane = 2:3 as eluant) to give 111-24 (1.217 g, 20%).

R/(silica-CH2Cl2): 0.53; 'H NMR (400 MHz, CDCI3): ô = 8.86-8.84 (m, 6H), 8.78 (d,

2H, J = 4.8 Hz), 8.43 (d, 2H, J = 8.2 Hz), 8.30 (d, 2H, J = 8.2 Hz), 8.22-8.20 (m, 6H), 7.79-

7.72 (m, 9H), 4.10 (s, 3H), -2.64 (br. s, 2H); LRESIMS (m/e): 673.4 ([M+H]*); HRESIMS

(m/e): calcd. for C46H33N4O2 ([M+H]*) 673.2604, found 673.2601; UV-Vis (CH2CI2) Wnm:

418.9, 515.0, 550.1, 591.0, 646.0. These data agree with the literature data.'*^

5-(4-Carboxyphenyl)-10,15,20-triphenyIporphyrin 111-22

Following the literature procedure, to a solution of 5-(4-methoxycarbonylphenyl)-

10,15,20-triphenylporphyrin 111-24 (1.22 g, 1.82 mmol) in EtOH (60 mL) was added 2 M aq.

KOH solution (120 mL) and the suspension was refluxed overnight. Cooled to r. t., the solvent was decanted and the crude mixture was washed with water, MeOH and hexane then evaporated to dryness. The residue was pre-adsorbed onto silica and chromatographed (silica,

5% MeOH in CH2CI2) to give 111-22 (0.85 g, 71%). R/(silica-5% MeOH in CH2CI2): 0.24; 'H NMR (400 MHz, de-acetone): Ô = 8.89-

8.87 (m, 8H), 8.49 (d, 2H, J = 8.0 Hz), 8.39 (d, 2H, J = 8.2 Hz), 8.27-8.24 (m, 6H), 7.86-7.82

(m, 9H), -2.75 (s, 2H); ESMS (m/e): 659.1 ([M+H]*). These data are consistent with the

hterature data.'^^

General Procedure for Esterification (GP-3)

A dry CH2CI2 solution (5 mL) of porphyrinoid acid (TPP-based 111-22 or BPD-based

111-23, 0.2 mmol), alcohol (0.2 mmol), coupler (EDC or DIC, 0.3 mmol), and DMAP (25 mg,

0.2 mmol) was stirred for 2 days, protected from the light. The crude mixture was

concentrated and purified by basic alumina (activity (II or III)) chromatography or prep. TLC.

The entire procedure was strictly protected from the light by using aluminum foil to cover all the reaction and purification apparatus and vessels. It was found preferable to carry out the work-up and chromatography in darkness during the night.

TPP-Ethyl Butyrate Complex 111-25

Ph

Ph

Following the general procedure (GP-2), desilylation of f'Zj-(5-ethoxyoct-4-enyloxy) triisopropylsilane III-16-Z (0.164 g, 0.5 mmol), followed by basic alumina chromatography (activity (III), CHzCh'.hexme = 1:4 as eluant) gave fZ>5-ethoxyoct-4-en-l-ol III-19-Z.

III-19-Z was immediately employed in the esterification of 5-(4-Carboxyphenyl)-

10,15,20-triphenylporphyrin 111-22 (165 mg, 0.25 mmol) using EDC (72 mg, 0.375 mmol) as coupler, following the general procedure (GP-3). The crude mixture was purified by basic alumina chromatography (activity (III), CH2Cl2:hexane = 4:1 as eluant) to give 111-25 (140 mg,

70% yield).

R/(alumina-CH2Cl2:hexane 4:1): 0.70; 'H-NMR (400 MHz, d

8.78 (m, 8H), 8.35 (d, 2H, J = 8.1 Hz), 8.25 (d, 2H, J = 8.2 Hz), 8.20-8.15 (m, 6H), 7.82-7.70

(m, 9H), 4.62 (t, IH, J = 7.2 Hz, A'), 4.44 (t, 2H, J = 6.5 Hz), 3.74 (q, 2H, J = 7.0 Hz), 2.31

(m, 2H), 2.09 (t, 2H, J = 7.4 Hz), 1.91-1.84 (m, 2H), 1.50-1.41 (m, 2H), 1.20 (t, 3H, J = 7.0

Hz), 0.91 (t, 3H, J = 7.4 Hz), -2.73 (s, 2H); '^C['H] NMR (100 MHz, de-acetone): ô = 166.8,

155.7 (A^), 147.4, 142.7, 135.3, 135.1, 131.0, 128.8, 128.6, 127.7, 121.4, 121.2, 119.6, 109.3

(A"), 65.5, 64.1, 34.3, 29.9, 22.1, 21.1, 15.8, 13.8; LRESIMS (m/e): 813.4 ([M+H]*);

HRESIMS (m/e): calcd. for C55H49N4O3 ([M+H]*) 813.3805, found 813.3796; Anal, calcd.

(found) for C55H48N4O3: C, 81.25 (81.16); H, 5.95 (6.02); N, 6.89 (7.25); UV-Vis (acetone)

Wnm(log e): 415 (5.67), 512 (4.29), 546 (3.98), 589 (3.82), 648 (3.87).

TPP-Ethyl Benzoate Complex 111-26 Following the general esterification procedure (GP-3), 5-(4-carboxyphenyl)-

10,15,20-triphenylporphyrin 111-22 (79 mg, 0.12 mmol) was esterified with (Z>5-ethoxy-5-

phenylpent-4-en-l-ol III-20-Z (25 mg, 0.12 mmol) using DIC coupler (25 mg, 0.2 mmol),

yielded 111-26 (82 mg, 81% yield) after basic alumina chromatography (activity (III),

CH2Cl2:hexane = 4:1 as eluant).

R/(alumina-CH2Cl2:hexane 2:1): 0.47; 'H-NMR (400 MHz, d^-acetone): ô = 8.84-

8.79 (m, 8H), 8.36 (d, 2H, J = 8.1 Hz), 8.24 (d, 2H, J = 8.2 Hz), 8.20-8.17 (m, 6H), 7,81-7.71

(m, 9H), 7.50-7.49 (m, 2H), 7.35-7.31 (m, 2H), 7.27-7.24 (m, IH), 5.48 (t, IH, J = 7.4 Hz, A^),

4.50 (t, 2H, J = 6.4 Hz), 3.69 (q, 2H, J = 7.0 Hz), 2.53 (m, 2H), 2.01-1.96 (m, 2H), 1.26 (t, 3H,

J = 7.0 Hz), -2.74 (s, 2H); '^C['H] NMR (100 MHz, d^-acetone): ô = 166.9, 155.3 (A^), 147.5,

142.8, 137.4, 135.4, 135.3, 132.0 (/3-carbons, not observed, inferred from the HMBC

correlation signal of the /3-protons), 131.0, 129.3, 128.9, 128.7, 127.8, 126.7, 121.5, 121.3,

119.7, 114.4 (A''), 66.7, 65.6, 29.8, 23.2, 15.8; LRESIMS (m/e): 847.4 ([M+Hf); HRESIMS

(m/e): calcd. for C58H47N4O3 ([M+H]*) 847.3648, found 847.3621; Anal, calcd. (found) for

C58H46N4O3: C, 82.24 (81.86); H, 5.47 (5.55); N, 6.61 (6.58); UV-Vis (CH2CI2) Wnm: 418,

515, 549, 591,650.

TPP-Methyl Pivalate Complex 111-27 Following the general esterification procedure (GP-3), 5-(4-carboxyphenyl)-

10,15,20-triphenylporphyrin 111-22 (132 mg, 0.2 mmol) was esterified with fZ>5-methoxy-

6,6-dimethylhept-4-en-l-ol 111-21 (32 mg, 0.19 mmol) using EDC coupler (58 mg, 0.3 mmol),

yielded 111-27 (111 mg, 72% yield) afl;er basic alumina chromatography (activity (HI),

CH2Cl2:hexane = 2:3 as eluant).

R/(silica-CHjCy: 0.53; 'H-NMR (400 MHz, CéDô): Ô = 8.96 (d, 2H, J = 4.8 Hz),

8.93 (s, 4H), 8.83 (d, 2H, J = 4.7 Hz), 8.49 (d, 2H, J = 7.9 Hz), 8.13-8.10 (m, 6H), 8.06 (d, 2H,

J = 7.9 Hz), 7.50-7.44 (m, 9H), 4.77 (t, IH, J = 7.1 Hz, A*), 4.44 (t, 2H, J = 6.5 Hz), 3.53 (s,

3H), 2.30-2.24 (m, 2H), 1.82-1.75 (m, 2H), 1.16 (s, 9H), -2.13 (s, 2H); '^Ci'R] NMR (100

MHz, CéDô): ô = 166.9, 166.8 (A^), 147.7, 143.1, 135.2, 132.0 (br., |3-carbons), 130.8, 128.5,

128.2, 127.3, 121.4, 121.2, 119.6, 107.7 (A^), 65.3, 61.7, 37.6, 30.0, 29.0, 23.3; LRESIMS

(m/e): 813.5 ([M+H]*); HRESIMS (m/e): calcd. for C55H49N4O3 ([M+H]*) 813.3805, found

813.3808; Anal, calcd. (found) for C55H48N4O3: C, 81.25 (81.24); H, 5.95 (6.11); N, 6.89

(6.78); UV-Vis (CH2CI2) Wnm: 419, 515, 549, 592, 649.

BPD-Ethyl Benzoate Complex 111-28

Following the general esterificadon procedure (GP-3), ring B-BPD-7^-monoacid III- 23 (160 mg, 0.22 mmol) was esterified with fZ>5-ethoxy-5-phenylpent-4-en-l-ol 111-20-2

(46 mg, 0.22 mmol) using DIC coupler (70 fiL, 0.44 mmol), yielded 111-28 (112 mg, 56% yield) after basic alumina chromatography (activity (III), CH2Cl2:hexane = 3:1 as eluant).

R/(alumina-CH2Cl2): 0.22; 'H-NMR (400 MHz, de-acetone): ô = 9.89 (s, IH), 9.86 (s,

IH), 9.57 (s, IH), 9.38 (s, IH), 8.28 (dd, IH, J = 11.6 Hz, J = 17.9 Hz), 7.84 (d, IH, J = 5.7

Hz), 7.69 (d, IH, J = 5.8 Hz), 7.56-7.52 (m, 2H), 7.40-7.36 (m, 2H), 7.32-7.27 (m, IH), 6.43

(dd, IH, J = 1.2 Hz, J = 17.9 Hz), 6.15 (dd, IH, J = 1.3 Hz, J = 11.6 Hz), 5.51 (t, IH, J = 7.3

Hz, A^), 5.18 (s, IH), 4.48-4.34 (m, 2H), 4.28-4.15 (m, 4H), 3.76 (q, 2H, J = 7.0 Hz), 3.66 (s,

3H), 3.59 (s, 3H), 3.58 (s, 3H), 3.48 (s, 3H), 3.40 (s, 3H), 3.22 (t, 2H, J = 7.6 Hz), 3.17 (t, 2H,

J = 7.6 Hz), 3.15 (s, 3H), 2.57-2.51 (m, 2H), 2.02-1.94 (m, 2H), 1.83 (s, 3H), 1.33 (t, 3H, J =

7.0 Hz), -2.27 (s, 2H); '^C['H] NMR (100 MHz, de-acetone): ô = 173.8, 173.5, 171.0, 167.3,

166.7, 156.6, 155.1 (A^), 153.9, 152.7, 152.5, 141.3, 139.3, 138.4, 137.6, 137.5, 137.3, 137.2,

134.9, 134.5, 134.2, 132.3, 131.6, 130.4, 129.2, 128.6, 126.6, 123.8, 121.2, 114.4 (ASnd7\

100.7, 99.7, 94.4, 92.6, 66.5, 65.2, 53.3, 51.7, 51.6, 51.5, 48.6, 37.4, 36.8, 29.8, 27.9, 23.0,

22.1, 21.7, 15.7, 12.4, 11.5, 11.0; LRESIMS (m/e): 907.4 ([M+H]*); HRESIMS (m/e): calcd. for C54H59N4O9 ([M+H]*) 907.4282, found 907.4318; UV-Vis (CH2CI2) Xmax/nm: 353, 432,

583, 629, 690.

5-[4-[N-isopropyl-N-(isopropylcarbamoyl)carbamoyl]]-10,15,20-triphenyIporphyrln 111-31 A THF solution (30 mL) of 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin 111-22

(0.3 g, 0.46 mmol) and DIC (85 ixL, 0.55 mmol) was stirred for 2 days. The crude mixture

was then concentrated and purified by sihca gel chromatography (1% MeOH in CH2CI2 as

eluant) to give 111-31 (0.28 g, 78% yield). Crystals of 111-31 were obtained by solvent

diffusion of hexane into its CH2CI2 solution.

R/(silica-l% MeOH in CH2CI2): 0.24; 'H-NMR (400 MHz, CDCI3): ô = 8.87-8.79

(m, 8H), 8.29 (d, 2H, J = 8.0 Hz), 8.21-8.20 (m, 6H), 7.95 (d, 2H, J = 8.0 Hz), 7.76-7.72 (m,

9H), 6.72 (m, IH), 4.81-4.72 (m, IH), 4.09-3.99 (m, IH), 1.61 (d, 6H, J = 6.8 Hz), 1.22 (d,

6H, J = 6.8 Hz), -2.78 (s, 2H); LRESIMS (m/e): 785.3 ([M+H]*); HRESIMS (m/e): calcd. for

C52H45N6O2 ([M+H]*) 785.3604, found 785.3607.

5.3.2 Photooxygenation

General Procedure for Photooxygenation (GP-4)

According to the experimental design elaborated in section 3.4.1, to a deuterated solution (ca. 0.5 mL) of a photosensitizer-drug complex (ca. 3 pmol) in a 5 mm NMR tube was added the internal standard, 1,3,5-trimethoxybenzene (ca. 0.5 mg, 3 /mol). A filtered visible light was shone onto the reaction solution and the temperature was maintained at r. t.

(or -78 °C). From time to time, the photoirradiation was interrupted and the NMR tube was capped and shaken vigorously before ca. 0.5 fiL of the reaction mixture was removed and injected into GC for the quantification of released drug. The head pressure and the injection temperature of GC were set to 15.2 psi and 220 °C respectively. Two temperature programs were employed: A. increasing from 80 °C (maintaining for 1 min) to 220 "C at 10 °C/min; and B. increasing from 40 °C (maintaining for 3 min) to 220 °C at 10 °C/min. The retention times

of 1,3,5-trimethoxybenzene for program A and B are 10.00 min and 16.07 min respectively.

Program A was generally applied except for the photooxygenation of the ethyl butyrate-

incorporated complexes, where Program B was used. Simuhaneously, the reaction mixture was characterized by 'H- ('^C['H]-) NMR spectroscopy, APT and 'H-'H COSY ('H-'^C

HMQC, HMBC) correlation(s) to monitor the reaction progress and calculate the conversions and yields, before the photoirradiation was continued for the next period. Such photoirradiation-characterization cycles were continued until most of the starting photosensitizer-drug complex was converted.

Determination of the Relative GC Response Factor

Based on Equation 3.1 of section 3.4.1, the relative GC response factors of ethyl butyrate and ethyl benzoate were determined (Table 5.1).

Table 5.1 Relative GC response factors for esters in Chapter Three

Ethyl Butyrate ^ Ethyl Benzoate Temp Program |B , A TR(min) ; 3.48 \ 5.90 Mol Ratio ! AvgGC Ratio | Mol Ratio î AvgGC Ratio : 1Ï13 i - ^ ^ _ Entries ; " ^ 0^5 : 0.44 \ 0^523 î 0639 : 0^226 0.16 ^0209 ' " i " 0^249 0.113 0.081 1 0.105 I 0.125 0.78 f 1.20 In CDCI3

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate

complex 111-25 (ca. 10 mg, 12 /tanol) and 1,3,5-trimethoxybenzene (ca. 2 mg, 11 punol) were

dissolved in 0.5 mL CDCI3 with an NMR-determined molar ratio of 1.27 (lll-25/intemal

standard). Photoirradiation of the reaction solution for 50 min yielded hydroperoxide 111-32

(42%), dioxetane 111-33 (39%), aldehyde 111-34 (8%) and ethyl butyrate (8%). The GC yield

of total releasable ethyl butyrate was 33%. The crude reaction mixture was concentrated and

cliromatographed on silica gel (CH2Cl2:hexane = 2:1) to furnish pure 111-34, Despite that III-

32 and 111-33 decomposed during the chromatography, their 'H and '^C['H] signals were

unambiguously assigned from the spectra of the crude photooxygenation mixture with the

assistance of COSY, HMQC and HMBC (see section 3.4.2.1 for detailed discussion).

Hydroperoxide 111-32 (not isolated, data were obtained from a mixture sample)

Ph

B* OOH

H-NMR (400 MHz, CDCI3, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.87-8.77 (m, 8H), 8.46-8.41 (m, 2H), 8.31-8.29 (m, 2H), 8.22-8.20 (m, 6H), 7.78-7.72 (m, 9H), 7.57 (s, IH, -OOH), 6.02 (tt, IH, J = 6.9 Hz, J = 15.9

Hz, B^), 5.63 (d, IH, J = 15.9 Hz, B^), 4.59 (t, 2H, J = 6.4 Hz), 3.68-3.53 (m, 2H), 2.73-2.68

(m, 2H), 1.78-1.68 (m, 2H), 1.46-1.36 (m, 2H), 1.25 (t, 3H, J = 7.1 Hz), 0.91 (t, 3H, J = 7.3

Hz), -2.77 (s, 2H); "C['H] NMR (100 MHz, CDCI3, peaks were extracted from the spectrmn

of the crude photooxygenation mixture): ô = 166.8, 147.2, 142.0, 134.5, 131.2 (br., /3-carbons),

130.9 (B\ 130.2 (B^), 129.6, 127.9, 127.8, 126.7, 120.6, 120.4; 118.5, 106.9 (B^), 64.1, 57.3,

37.0, 32.1, 17.0, 15.5, 14.2; ESIMS (m/e, resuk of the mixture sample): 845.3 ([M+H]*).

Dioxetane 111-33 (not isolated, data were obtained from a mixture sample)

R/(silica-CH2Cl2): 0.55; 'H-NMR (400 MHz, CDCI3,peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.87-8.77 (m, 8H), 8.46-8.41 (m, 2H),

8.31-8.29 (m, 2H), 8.22-8.20 (m, 6H), 7.78-7.72 (m, 9H), 5.43 (t, IH, J = 7.0 Hz, C^), 4.53-

4.50 (m, 2H), 3.81-3.63 (m, 2H), 2.23-2.17 (m, 2H), 2.13-1.92 (m, 2H), 1.92-1.84 (m, 2H),

1.48-1.38 (m, 2H), 1.31 (t, 3H, J = 7.0 Hz), 1.00 (t, 3H, J = 7.4 Hz), -2.77 (s, 2H); "C['H]

NMR (100 MHz, CDCI3, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 166.8, 147.2, 142.0, 134.5, 131.2 (br., /3-carbons), 129.6,

127.9, 127.8, 126.7, 120.6, 120.4, 118.5, 110.1 (C^), 89.3 (C\ 64.8, 57.5, 37.5, 26.1, 23.5, 16.3, 15.7, 14.1; ESMS (m/e, result of the mixture sample): 845.3 ([M+H]*).

Aldehyde 111-34

Ph

H

% (siUca-CHaClî): 0.40; 'H-NMR (300 MHz, CD2CI2): ô = 9.90 (s, IH, D^-CHO),

8.89-8.81 (m, 8H), 8.42 (d, 2H, J = 8.4 Hz), 8.32 (d, 2H, J = 8.4 Hz), 8.24-8.20 (m, 6H), 7.78-

7.76 (m, 9H), 4.53 (t, IH, J - 6.5 Hz), 2.76 (t, 2H, J = 7.3 Hz), 2.28-2.19 (m, 2H), -2.84 (s,

2H); ESIMS (m/e): 729.5 ([M+H]*).

In dfi-acetone

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate complex 111-25 (ca. 10 mg, 12 /mol) and 1,3,5-trimethoxybenzene (ca. 2 mg, 11 /miol) were dissolved in 0.5 mL do-acetone with an NMR-determined molar ratio of 1.22 (lll-25/intemal standard). Photoirradiation of the reaction solution for 30 min yielded hydroperoxide 111-32

(42%), dioxetane 111-33 (10%), aldehyde 111-34 (7%) and ethyl butyrate (12%). The GC yield of total releasable ethyl butyrate was 19%.

In CD2CI2

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate complex 111-25 (ca. 11 mg, 13 jumol) and 1,3,5-trimethoxybenzene (ca. 2 mg, 11 /miol) were

dissolved in 0.5 mL CD2CI3 with an NMR-determined molar ratio of 1.02 (lll-25/intemal

standard) Photoirradiation of the reaction solution for 4 h at -78 °C yielded hydroperoxide III-

32 (33%), aldehyde 111-34 (54%) and ethyl butyrate (60%). The GC yield of total releasable

ethyl butyrate was 53%.

5.3.2.2 Photooxygenation of TPP-Ethyl Benzoate Complex 111-26

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Benzoate

complex 111-26 (ca. 1.8 mg, 2 jumol) and 1,3,5-trimethoxybenzene (ca. 0.3 mg, 2 /miol) were

dissolved in 0.5 mL CÔDÔ with an NMR-determined molar ratio of 1.11 (lll-26/intemal

standard). Photoirradiation of the reaction solution for 22 min yielded hydroperoxide 111-35

(85%), aldehyde 111-34 (10%) and ethyl butyrate (7%). The GC yield of total releasable ethyl benzoate was 13%>.

Hydroperoxide 111-35 (not isolated, data were obtained from a mixture sample)

Ph

Ph

R/(silica-CH2Cl2): 0.11; 'H-NMR (400 MHz, C(X)6, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.97 (d, 2H, J = 4.6 Hz), 8.92 (s, 4H), 8.82 (d, 2H, J = 4.6 Hz), 8.37 (d, 2H, J = 8.2 Hz), 8.13-8.08 (m, 6H), 8.04 (d, 2H, J = 8.2 Hz),

7.69 (d, 2H, J = 8.4 Hz), 7.51-7.43 (m, 9H), 7.25-7.04 (m, 3H), 6.03 (tt, IH, J = 6.9 Hz, J =

15.6 Hz, B^), 5.76 (d, IH, J = 15.8 Hz, B'*), 4.27 (t, 2H, J = 6.2 Hz), 3.68-3.53 (m, 2H), 2.25-

2.20 (m, 2H), 1.18 (t, 3H, J = 7.1 Hz), -2.14 (s, 2H); ESIMS (m/e, resuit of the mixture

sample): 880.9 ([M+H]*).

5.3.2.3 Photooxygenation ofBPD-Ethyl Benzoate Complex 111-28

In CéDe

Following the general photooxygenation procedure (GP-4), BPD-Ethyl Benzoate

complex 111-28 {ca. 2 mg, 2 jumol) and 1,3,5-trimethoxybenzene {ca. 0.5 mg, 3 /rniol) were

dissolved in 0.5 mL CÔDÔ with an NMR-determined molar ratio of 0.76 (lll-28/intemal

standard). After photoirradiation of the reaction solution for 50 min, 89% of 111-28 was

converted to hydroperoxide III-36-XA' (71%). The GC yield of total releasable ethyl benzoate

was 10%.

In de-acetone

Following the general photooxygenation procedure (GP-4), BPD-Ethyl Benzoate complex 111-28 {ca. 3 mg, 3 jjtmol) and 1,3,5-trimethoxybenzene (ca. 0.3 mg, 2 pmol) were dissolved in 0.5 mL d^-acetone with an NMR-determined molar ratio of 1.55 (ni-28/intemal standard). Photoirradiation of the reaction solution for 80 min yielded hydroperoxide 111-36-

X/Y (63%) and ethyl benzoate (8%). The GC yield of total releasable ethyl benzoate was 15%. 5.3.2.4 Photooxygenation ofTPP-Methyl Pivalate Complex 111-27

Following the general photooxygenation procedure (GP-4), TPP-Methyl Pivalate complex 111-27 (ca. 2 mg, 2.5 /unol) and 1,3,5-trimethoxybenzene (ca. 0.3 mg, 2 /miol) were dissolved in 0.5 mL CeDe with an NMR-determined molar ratio of 0.99 (lll-27/intemal standard). Photo irradiation of the reaction solution for 67 min yielded hydroperoxide 111-37

(58%), dioxetane 111-38 (19%) and aldehyde 111-34 (2%).

Hydroperoxide 111-37 (not isolated, data were obtained from a mixture sample)

'H-NMR (400 MHz, C^De, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.96 (d, 2H, J = 4.8 Hz), 8.92 (s, 4H), 8.81 (d, 2H, J = 4.8 Hz),

8.46 (d, 2H, J = 8.0 Hz), 8.13-8.10 (m, 6H), 8.05 (d, 2H, J = 8.0 Hz), 7.49-7.41 (m, 9H), 6.95

(s, IH, -OOH), 5.87 (tt, IH, J = 7.1 Hz, J = 15.9 Hz, B^), 5.47 (d, IH, J = 16.0 Hz, B'*), 4.39-

4.34 (m, 2H), 3.43 (s, 3H), 2.40-2.35 (m, 2H), 1.17 (s, 9H), -2.14 (s, 2H); ESIMS (m/e, result of the mixture sample): 867.4 ([M+Na]*). Ph

' H-NMR (400 MHz, CeDô, peaks were extracted from the spectrum of the crude

photooxygenation mixture): ô = 8.96 (d, 2H, J = 4.8 Hz), 8.92 (s, 4H), 8.81 (d, 2H, J = 4.8 Hz),

8.49 (d, 2H, J = 8.1 Hz), 8.13-8.10 (m, 6H), 8.05 (d, 2H, J = 8.0 Hz), 7.49-7.41 (m, 9H), 5.55-

5.51 (m, IH, C^), 4.41-4.36 (m, 2H), 3.79 (s, 3H), 2.00-1.92 (m, 2H), 1.83-1.79 (m, 2H), 1.03

(s, 9H), -2.14 (s, 2H); ESIMS (m/e, resuh of the mixture sample): 867.4 ([M+Na]*).

5.4 Experimental Data for Chapter Four

5.4.1 Synthesis

4-(6-methoxynaphthalen-2-yl)-2-methylbutanal IV-9

To a dry THF suspension (5 mL) of triphenyl-(methoxymethyl) phosphonium chloride (0.45 g, 1.3 mmol) at -78 "C was added lithium bis(trimethylsilyl)amide solution (2 mL, 1 M solution in THF, 2 mmol) dropwise under Ar. Stirring was continued for 1 h before the solution was slowly warmed to 25 °C and stirred for another 2 h. A THF solution (2 mL)

of nabumetone (0.23 g, 1 mmol) was then added dropwise to the reaction mixture and stirring

was continued overnight. The reaction mixture was quenched with sat. NH4CI aq. solution,

extracted with ether and washed with water. Solvent removal and subsequent silica gel

chromatography (CHaCliihexane = 1:2) gave 2-methoxy-6-(4-methoxy-3-methylbut- 3-

enyl)naphthalene IV-8 (0.18 g, 70% yield).

To a THF solution (5 mL) of the above enol ether IV-8 was added 5 drops of conc.

HCI and the resulting mixture was stirred for 2 h before diluting with 100 mL ether and

washing with water. The organic fi-action was dried over sodium sulfate and concentrated

before sihca gel chromatography (CH2Cl2:hexane = 2:1) to give IV-9 (0.14 g, 57% yield over

2 steps).

R/(silica- CH2Cl2:hexane = 4:1): 0.43; 'H-NMR (400 MHz, CDCI3): ô = 9.62 (s, IH),

7.65 (m, 2H), 7.53 (s, IH), 7.27 (m, IH), 7.13-7.10 (m, 2H), 3.89 (s, 3H), 2.81-2.75 (m, 2H),

2.42-2.37 (m, IH), 2.18-2.09 (m, IH), 1.77-1.68 (m, IH), 1.15 (d, 3H, J = 7.2 Hz); '^C['H]

NMR (100 MHz, CDCI3): ô = 204.8, 157.3, 136.5, 133.1, 129.1, 128.9, 127.6, 127.0, 126.4,

118.8, 105.7, 55.3, 45.6, 33.0, 32.1, 13.4; LRESIMS (m/e): 265.3 ([M+Na]*); HRESIMS

(m/e): calcd. for Ci6Hi802Na ([M+Na]*) 265.1204, found 265.1209; Anal, calcd. (found) for

C16H18O2: C, 79.31 (79.47); H, 7.49 (7.66). 5-[4-[N-MethyI-N-(2-(inethylamino)ethyl)carbainoyl]phenyl]-10,15,20-triphenylporphyrin

IV-10

Ph

A dry DMF solution (10 mL) of N,N'-dimethylethylenediamine (0.16 mL, 1.5 mmol),

5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin 111-22 (0.2 g, 0.3 mmol), triethylamine (46

/LiL, 0.33 mmol) and 0-(benzotriazol-l-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate

(0.11 g, 0.33 mmol) was stirred for 20 h before solvent evaporation and silica gel chromatography (10% MeOH in CH2CI2 as eluant). Recrystallization of the crude product with CH2Cl2/hexane gave IV-10 (0.11 g, 51% yield).

R/(silica-10% MeOH in CH2CI2): 0.14; 'H NMR (300 MHz, CDCI3): ô = 8.82-8.79

(m, 8H), 8.26 (d, 2H, J = 7.8 Hz), 8.18-8.11 (m, 6H), 7.99 (d, 2H, J = 7.8 Hz), 7.73-7.62 (m,

9H), 4.15 (m, 2H), 3.51 (m, 2H), 3.44 (s, 3H), 2.95 (s, 3H), -2.81 (s, 2H); '^C['H] NMR (100

MHz, CDCI3): ô = 173.6, 144.4, 141.8, 134.3, 133.9, 127.6, 126.5, 125.7, 120.4, 120.2, 118.2,

46.9, 45.1, 38.9, 33.2; LRESIMS (m/e): 729.5 ([M+H]*); HRESIMS (m/e): calcd. for

C49H41N6O ([M+H]*) 729.3342, found 729.3353; UV-Vis (CH2CI2) Wnm: 417.9, 514.0,

549.1,592.0, 647.0.

(5-Hydroxypentoxy)(tert-butyI)dimethylsilane IV-6

To a 100 mL dry THF suspension of NaH (3.9 g, 60% suspension in minerai oil, 99 mmol) at 0 °C was added dropwise a THF solution (20 mL) of 1,5-pentadiol (9.5 mL, 90 mmol), followed by the addition of a THF solution (30 mL) of tert-butyldimethylsilyl chloride

(13.6 g, 90 mmol). The reaction solution was stirred overnight before being quenched with sat.

NaHCOa aq. solution and extracted with ether. The organic phase was concentrated and chromatographed on silica gel (ethyl acetate:hexane = 1:4 as eluant) to gave IV-6 (12.2 g,

62% yield).

R/(sihca-ethyl acetate:hexane= 1:2): 0.4; 'H NMR (400 MHz, CDCI3): ô = 3.56-3.52

(m, 4H), 2.56-2.48 (br. s, IH), 1.52-1.44 (m, 4H), 1.36-1.30 (m, 2H), 0.82 (s, 9H), -0.02 (s,

6H); "C['H] NMR (100 MHz, CDCI3): ô = 63.1, 62.5, 32.4, 32.3, 25.8, 21.9, 18.2, -5.4;

LRESIMS (m/e): 241.4 ([M+Na]*); HRESIMS (m/e): calcd. for CuHsôOzNaSi ([M+Na]*)

241.1600, found 241.1595. These data agree with the literature data.^^^

[Bis(phenylthio)methyl]tributylstannane IV-2

SPh

BuaSn SPh

To a dry THF solution (20 mL) of bis(phenylthio)methane (2.32 g, 10 mmol) at -78

°C under Ar was added dropwise a LDA solution (5.5 mL, 2 M solution in heptane/THF/ethylbenzene, 11 mmol). The reaction solution was stirred for 1 h before the addition of a THF solution (10 mL) of tributyltin chloride (3 mL, 11 mmol) and stirring was continued overnight. The reaction mixture was quenched with water, extracted with hexane and dried over sodium sulfate. The solution was then concentrated and chromatographed on sihca gel (hexane as eluant) to gave IV-2 (5 g, 95% yield).

R/(silica- hexane): 0.16; 'H NMR (400 MHz, CDCI3): ô = 7.43-7.41 (m, 4H), 7.21-

7.16 (m, 6H), 4.31 (s, IH), 1.54-1.49 (m, 6H), 1.35-1.27 (m, 6H), 1.01-0.97 (m, 6H), 0.91 (t. 9H, J = 7.3 Hz); '^C['H] NMR (100 MHz, CDCI3): 5 = 137.6, 130.9, 130.8, 128.6, 126.7, 36.4,

36.3, 28.8, 27.3, 13.6, 11.0; LRESIMS (m/e): 544.9 ([M+Na]*); HRESIMS (m/e): calcd. for

C25H38S2SnNa ([M+Na]*) 545.1335, found 545.1344; Anal, calcd. (found) for C25H38S2Sn: C,

57.59 (57.80); H, 7.35 (7.60). No spectroscopic data has been reported for this known

compound.

[5-(Bisphenylthiomethoxy)pentyIoxy](tert-butyl)dimethyIsilane IV-7

Using a modified literature procedure,'^^ to a 100 mL dry THF suspension of LiBr

(4.3 g, 50 mmol) and (5-hydroxypentoxy)tert-butyldimethylsilane IV-6 (5.5 g, 25 mmol) at 0

°C under Ar was added dropwise n-butyllithium solution (16 mL, 1.6 M solution in hexane,

25 mmol) and the reaction mixture was stirred for 30 min, before it was cooled to -40 °C and

CuBr2 (12.3 g, 55 mmol) was then added. Stirring was continued for 30 min before a THF

solution (100 mL) of (bis(phenylthio)methyl)tributylstannane IV-2 (13.1 g, 25 mmol) was added. The reaction mixture was stirred overnight while slowly warmed to 25 °C, before it was quenched with 3.5% ammonium hydroxide aq. solution and the insoluble materials were filtered off. The filtrate was then concentrated and chromatographed on silica gel

(CH2Cl2:hexane = 1:1 as eluant) to gave IV-7 (6.5 g, 58% yield).

R/(sihca- CH2Cl2:hexane = 1:4): 0.15; 'H NMR (400 MHz, C(,D(,): ô = 7.50-7.47 (m,

4H), 7.03-6.94 (m, 6H), 6.27 (s, IH), 3.72 (t, 2H, J = 6.4 Hz), 3.42 (t, 2H, J = 6.3 Hz), 1.45-

1.33 (m, 4H), 1.27-1.21 (m, 2H), 0.98 (s, 9H), 0.05 (s, 6H); '^C['H] NMR (100 MHz, CM:

ô = 135.1, 133.0, 129.5, 128.2, 94.0, 66.4, 63.4, 33.1, 29.6, 26.5, 23.1, 18.9, -5.38; LRESIMS (raye): 471.2 ([M+Na]*); HRESIMS (m/e): calcd. for C24H3602S2SiNa ([M+Na]*) 471.1824,

found 471.1842; Anal, calcd. (found) for C24H3602S2Si: C, 64.23 (64.42); H, 8.09 (7.93).

Methyl 2-(4-isobutylphenyl)propanoate (Methyl ester of Ibuprofen) IV-12

To a methanol solution (30 mL) of 2-(4-isobutylphenyl)propanoic acid (ibuprofen,

0.5 g, 2.4 mmol) was added 3 drops of conc. H2SO4 and the reaction mixture was stirred for 4

h before it was diluted with CH2CI2, washed with sat. NaHC03 aq. solution and dried over

sodium sulfate. Solvent evaporation gave IV-12 quantitatively (0.53 g).

'H NMR (400 MHz, CeDe): ô = 7.24 (d, 2H, J = 8.1 Hz), 6.98 (d, 2H, J = 8.0 Hz),

3.57 (q, IH, J = 7.1 Hz), 3.25 (s, 3H), 2.29 (d, 2H, J = 7.2 Hz), 1.74-1.67 ( m, IH), 1.42 (d,

3H, J = 7.1 Hz), 0.80 (d, 6H, J = 6.6 Hz); '^C['H] NMR (100 MHz, CeDe): ô = 174.9, 141.0,

139.0, 130.0, 128.0, 51.7, 45.7, 45.6, 30.8, 22.8, 19.3; LRESIMS (m/e): 243.2 ([M+Na]*);

HRESIMS (m/e): calcd. for Ci4H2o02Na ([M+Na]*) 243.1361, found 243.1360. These data are consistent with the literature data.'^'^^

(lS>Methyl 2-(6-methoxynaphthalen-2-yI)propanoate (Methyl ester of Naproxen) IV-13

Following the preparation procedure for IV-12, naproxen, (S)-2-(6 - methoxynaphthalen-2-yl)propanoic acid (0.5 g, 2.2 mmol) was converted to IV-13 quantitatively (0.54 g). 'h NMR (400 MHz, CDCI3): ô = 7.62 (s, IH), 7.57 (d, IH, J = 8.5 Hz), 7.48-7.45 (m,

2H), 7.18 (d, m, J = 2.6 Hz), 6.89 (d, IH, J = 2.4 Hz), 3.71 (q, IH, J = 7.1 Hz), 3.36 (s, 3H),

3.28 (s, 3H), 1.52 (d, 3H, J = 7.1 Hz); LRESIMS (m/e): 267.0 ([M+Na]*); HRESIMS (m/e):

calcd. for CisHiôOsNa ([M+Na]*) 267.0997, found 267.0999. These data are consistent with

the literature data.^^°

General Procedure for Takeda Alkoxymethylenation'*'^ (GP-5)

Mg turnings (86.4 mg, 3.6 mmol), Cp2TiCl2 (0.75 g, 3 mmol) and finely powdered 4

 molecular sieves (300 mg) were dried by heating in vacuo. After coohng under Ar, dry THF

(5 mL) and P(0Et)3 (1.05 mL, 6 mmol) were added to the system and the reaction solution was stirred at 25 "C for 3 h, before the addition of a THF solution (1.5 mL) of [5-

(Bisphenylthiomethoxy)pentyloxy](tert-butyl)dimethylsilane IV-7 (0.34 g, 0.75 mmol) and stirring was continued for 15 min. A THF solution (2.5 mL) of carboxyhc acid derivative substrate (0.5 mmol) was then added dropwise over 10 min to the system and stirring was continued for another 3 h. The reaction was quenched with 1 M aq. NaOH solution and the insoluble materials were filtered off through Celite and washed with ether. The layers were separated and the aq. layer was extracted with ether. The combined organic extracts were dried over sodium sulfate before they were concentrated and chromatographed on basic alumina (activity (II)) to furnish enol ether products.

2,2,3,3-TetramethyI-l2-propyi-4,l 0,13-trioxa-3-silapentadec-l 1-ene IV-14 Following the general procedure (GP-5), ethyl butyrate (71 iiL, 0.5 mmol) was

alkoxymethylenated. The resulting crude mixture was concentrated and chromatographed on

basic alumina (activity (II), CH2Cl2:hexane = 1:5 as eluant) to yield IV-14-Z (4 mg, 2% yield),

a IV-14-Z/E mixture 1 (54 mg, 33% yield, Z:E = 17:83) and a Wf-IA-UE mixture 2 (33 mg,

20% yield, Z:E = 71:29). The combined yield for IV-14-Z/E generated in this reaction was

55% with a stereoselectivity of Z:E = 39:61.

rZ>Isomer IV-14-Z

R/(silica- CH2CI2): 0.28; 'H NMR (400 MHz, CeDe): ô = 5.29 (s, IH), 4.17 (q, 2H, J

= 7.0 Hz), 3.51 (t, 2H, J = 6.1 Hz), 3.43 (t, 2H, J = 6.3 Hz), 1.92 (t, 2H, J = 7.2 Hz), 1.61-1.35

(m, 8H), 1.25 (t, 3H, J = 7.0 Hz), 0.99 (s, 9H), 0.93 (t, 3H, J = 7.4 Hz), 0.06 (s, 6H); '^C[^H]

NMR (100 MHz, CeDe): ô = 138.4, 127.8, 72.2, 65.6, 62.8, 33.5, 32.5, 29.5, 25.8, 22.4, 20.7,

18.1, 15.7, 13.4, -5.5; LRESIMS (m/e): 353.3 ([M+Naf ).

2,2,3,3-Tetramethyl-12-phenyl-4,10,13-trioxa-3-silapentadec-ll-ene IV-15

Following the general procedure (GP-5), ethyl benzoate (72 fiL, 0.5 mmol) was alkoxymethylenated. The resuhing crude mixture was concentrated and chromatographed on basic alumina (activity (II), CH2Cl2:hexane = 1:6 as eluant) to yield IV-15-Z (24.9 mg, 14% yield) and a IV-15-27E mixture (43.6 mg, 24% yield, Z:E = 86:14). The combined yield for

IV-15-Z/E generated in this reaction was 38% with a stereoselectivity of Z:E = 91:9. rZ>Isomer IV-15-Z

R/(silica- CH2CI2): 0.45; 'H NMR (400 MHz, CôDe): ô = 7.51 (d, 2H, J = 8.5 Hz),

7.21-7.17 (m, 2H), 7.10-7.07 (m, IH), 6.13 (s, IH), 4.03 (q, 2H, J = 7.0 Hz), 3.51-3.47 (m,

4H), 1.47-1.35 (m, 6H), 1.27 (t, 3H, J - 7.0 Hz), 0.99 (s, 9H), 0.06 (s, 6H); ''C['H] NMR

(100 MHz, CéDô): ô = 139.0, 137.0, 134.4, 129.0, 127.3, 124.9, 73.4, 67.1, 63.5, 33.2, 30.3,

26.5, 23.0, 18.9, 16.2, -4.8; LRESIMS (m/e): 387.2 ([M+Na]*); HRESIMS (m/e): calcd. for

C2iH3603SiNa ([M+Na]*) 387.2331, found 387.2340.

tert-Butyldimethyl[5-[(tetrahydro-2H-pyran-2-yIidene)methoxy]pentyloxy]silane IV-16

Following the general procedure (GP-5), ô-valerolactone (45 /iL, 0.5 mmol) was

alkoxymethylenated. The resulting crude mixture was concentrated and chromatographed on basic alumina (activity (II), CH2Cl2:hexane = 1:5 as eluant) to yield IV-16-Z (30.5 mg, 19% yield), IV-16-E (52.1 mg, 33% yield) and a IV-16-Z/E mixture (30.5 mg, 19% yield, Z:E =

49:51). The combined yield for IV-16-Z/E generated in this reaction was 72% with a stereoselectivity of Z:E = 40:60.

(Z>Isomer IV-16-Z

R/(silica- CH2CI2): 0.12; 'H NMR (400 MHz, CÔDÔ): Ô = 5.32 (s, IH), 3.69 (m, 2H),

3.56 (t, 2H, J = 6.4 Hz), 3.48 (t, 2H, J = 6.1 Hz), 1.87 (m, 2H), 1.58-1.27 (m, lOH), 0.98 (s,

9H), 0.05 (s, 6H); '^C['H] NMR (100 MHz, CéDf,): ô = 137.4, 128.9, 72.7, 69.8, 63.5, 33.3,

30.3, 27.0, 26.6, 26.5, 24.8, 23.0, 18.9, -4.8; LRESIMS (m/e): 337.1 ([M+Na]*); HRESIMS (m/e): calcd. for Ci7H3403SiNa ([M+Naf) 337.2175, found 337.2172; Anal, calcd. (found)

for C,7H3403Si: C, 64.92 (65.30); H, 10.90 (10.97).

r£>Isomer IV-16-E

R/(silica- CH2CI2): 0.19; NMR (400 MHz, CeDô): ô = 6.29 (s, IH), 3.66 (m, 2H),

3.49 (t, 2H, J = 6.2 Hz), 3.40 (t, 2H, J = 6.4 Hz), 2.44 (t, 2H, J = 6.1 Hz), 1.44-1.33 (m, lOH),

0.99 (s, 9H), 0.06 (s, 6H); "C['H] NMR (100 MHz, CeDe): ô = 142.6, 133.1, 72.7, 71.3, 63.5,

32.3, 30.1, 27.0, 26.5, 23.9, 23.0, 18.9, -4.8; LRESIMS (m/e): 337.1 ([M+Naf ).

3-[l-(4-Isobutylphenyl)ethyI]-12,12,13,13-tetramethyl-2,5,ll-trioxa-12-silatetradec-3-ene

IV-17

Following the general procedure (GP-5), methyl 2-(4-isobutylphenyl)propanoate IV-

12 (0.11 g, 0.5 mmol) was alkoxymethylenated. The resulting crude mixture was concentrated and chromatographed on basic alumina (activity (II), CH2Cl2:hexane = 1:8 as eluant) to yield

IV-17-Z (32 mg, 15% yield), a IV-17-Z/E mixture 1 (34.1 mg, 16% yield, Z:E = 26:74) and a

IV-17-Z/E mixture 2 (68.5 mg, 32% yield, Z:E = 65:35). The combined yield for IV-17-Z/E generated in this reaction was 63% with a stereoselectivity of Z:E = 63:37.

rZ>Isomer IV-17-Z

R^silica- CH2CI2): 0.35; 'H NMR (400 MHz, CJDe): ô = 7.34 (d, 2H, J = 8.0 Hz),

7.07 (d, 2H, J = 8.1 Hz), 5.45 (s, IH), 3.74 (s, 3H), 3.49 (t, 2H, J = 6.0 Hz), 3.38 (t, 2H, J = 6.3 Hz), 3.36-3.33 (m, IH), 2.38 (d, 2H, J = 7.2 Hz), 1.77-1.72 (m, IH), 1.45 (d, 3H, J = 7.1

Hz), 1.48-1.32 (m, 6H), 0.98 (s, 9H), 0.86 (d, 6H, J = 6.6 Hz), 0.05 (s, 6H); '^C['H] NMR (75

MHz, QDô): Ô = 144.6, 142.8, 140.0, 129.7, 129.6, 128.1, 73.0, 63.4, 59.8, 45.8, 42.4, 33.2,

30.9, 30.2, 26.5, 23.1, 22.9, 19.9, 18.9, -4.8; LRESIMS (m/e): 457.3 ([M+Na]*); HRESIMS

(m/e): calcd. for C26H4603SiNa ([M+Na]*) 457.3114, found 457.3116.

r5>3-[l-(6-methoxynaphthaIen-2-yl)ethyl]-12,12,13,13-tetramethyl-2,5,ll-trioxa-12- silatetradec-3-ene IV-18

Following the general procedure (GP-5), (5j-Methyl 2-(6-methoxynaphthalen- 2- yl)propanoate IV-13 (0.12 g, 0.5 mmol) was alkoxymethylenated. The resulting crude mixture was concentrated and chromatographed on basic alumina (activity (II), CH2Cl2:hexane = 1:8 as eluant) to yield IV-18-Z (30.8 mg, 13% yield), IV-18-E (23 mg, 10% yield) and a IV-18-

Z/E mixture (37 mg, 16% yield, Z:E = 65:35). The combined yield for IV-18-Z/E generated in this reaction was 40% with a stereoselectivity of Z:E = 61:39.

(Z>Isomer IV-18-Z

R/(silica- CH2CI2): 0.29; 'H NMR (400 MHz, CôDe): ô = 7.74 (s, IH), 7.66 (d, IH, J

= 8.5 Hz), 7.57 (d, IH, J = 8.6 Hz), 7.56 (d, IH, J = 8.9 Hz), 7.20 (dd, IH, J = 2.5 Hz, J = 8.9

Hz), 6.98 (d, IH, J = 2.4 Hz), 5.51 (s, IH), 3.75 (s, 3H), 3.49 (t, 2H, J = 6.0 Hz), 3.53-3.47(m,

IH), 3.41 (s, 3H), 3.40 (t, 2H, J = 6.2 Hz), 1.54 (d, 3H, J = 7.1 Hz), 1.53-1.35 (m, 6H), 0.98 (s,

9H), 0.05 (m, 6H); '^C['H] NMR (lOOM Hz, h = 158.3, 144.4, 140.4, 134.4, 130.1, 130.0, 128.7, 127.7, 127.3, 126.5, 119.4, 106.3, 73.0, 63.4, 59.8, 55.1, 42.7, 33.2, 30.2, 26.5,

23.0, 19.7, 18.8, -4.8; LRESIMS (m/e): 481.1 ([M+Na]*); Anal, calcd. (found) for C27H4204Si:

C, 70.70 (70.99); H, 9.23 (9.17).

(£>Isomer IV-18-E

R/(silica-CH2Cl2): 0.48; 'H-NMR (400 MHz, CeDe): ô = 7.90 (s, IH), 7.79-7.76 (m,

IH), 7.68 (d, IH, J = 8.5 Hz), 7.59 (d, IH, J = 8.9 Hz), 7.20-7.17 (m, IH), 6.95 (d, IH, J = 2.3

Hz), 5.60 (s, IH), 4.71-4.68 (q, IH, J = 7.2 Hz), 3.53 (t, 2H, J = 5.9 Hz), 3.49 (t, 2H, J = 6.4

Hz), 3.38 (s, 3H), 3.13 (s, 3H), 1.71 (d, 3H, J = 7.3 Hz), 1.62-1.57 (m, 2H), 1.52-1.46 (m, 4H),

0.99 (s, 9H), 0.07 (s, 6H); '^C['H] NMR (100 MHz, CeDs): ô = 158.1, 151.1, 140.7, 134.3,

130.1, 130.0, 128.0, 127.2, 126.3, 124.9, 119.3, 106.3, 73.3, 63.5, 55.5, 55.1, 38.0, 33.3, 30.2,

26.5, 23.2, 18.8, 18.4, -4.7; LRESIMS (m/e): 481.2 ([M+Na]*); HRESIMS (m/e): calcd. for

C27H4204NaSi ([M+Na]*) 481.2750, found 481.2746.

N-[2-[5-(tert-ButyldimethylsilyIoxy)pentyloxy]-l-phenylvinyI]-N-methylanilme IV-19

Following the general procedure (GP-5), N-methylbenzanilide (50 mg, 0.24 mmol) was converted to a IV-19-ZyE mixture (52 mg, 51% yield, Z:E = 83:17), after basic alumina

(activity (II)) chromatography (hexane as eluant). fZ>Isomer IV-19-Z (not isolated, data were obtained from the above mixture sample)

'H NMR (400 MHz, C^D^, peaks were extracted from the spectrum of the Z/E mixture): ô = 7.30 (d, 2H, J = 7.4 Hz), 7.22-7.17 (m, 2H), 7.15-7.11 (m, 2H), 7.07-7.03 (m,

IH), 6.83 (d, 2H, J = 8.0 Hz), 6.78-6.75 (m, IH), 6.29 (s, IH), 3.44 (t, 2H, J = 6.3 Hz), 3.40 (t,

2H, J = 6.4 Hz), 3.04 (s, 3H), 1.36-1.27 (m, 4H), 1.21-1.15 (m, 2H), 0.99 (s, 9H), 0.07 (s, 6H);

'^C['H] NMR (lOOM Hz, CôDe, peaks were extracted from the spectrum of the Z/E mixture):

ô = 149.2, 143.2, 137.9, 129.5, 129.3, 127.2, 126.4, 125.5, 117.5, 113.7, 73.5, 63.4, 38.2, 33.1,

30.3, 26.5, 22.7, 18.9, -4.8; LRESIMS (m/e, result of the mixture sample): 426.3 ([M+H]*);

HRESIMS (m/e, resuU of the mixture sample): calcd. for CîôîLtoNOaSi ([M+H]*) 426.2828, found 426.2824.

l-[2-[5-(tert-ButyldlmethylsilyIoxy)pentyloxy]-l-phenylvinyl]piperidine IV-20

Following the general procedure (GP-5), 1-benzylpiperidine (95 mg, 0.5 mmol) was alkoxymethylenated. The resulting crude mixture was concentrated and chromatographed on basic alumina (activity (II), hexane as eluant) to yield IV-20-Z (15 mg, 7% yield) and a IV-20-

Z/E mixture (38 mg, 19% yield, Z:E = 89:11). The combined yield for IV-20-Z/E generated in this reaction was 26% with a stereoselectivity of Z:E = 92:8.

rZ>Isoiner IV-20-Z

R/(silica- CH2CI2): 0.13; 'H NMR (400M Hz, CÔDÈ): Ô = 7.63 (d, 2H, J = 7.9 Hz), 7.24 (t, 2H, J = 7.5 Hz), 7.16-7.13 (m, IH), 5.79 (s, IH), 3.51 (t, 2H, J = 6.0 Hz), 3.45 (t, 2H,

J = 6.3 Hz), 3.15 (m, 4H), 1.58-1.38 (m, 12H), 0.99 (s, 9H), 0.07 (s, 6H); ''C['H] NMR

(lOOM HZ, CÔDÔ): Ô = 140.2, 134.8, 132.8, 128.8, 127.7, 127.5, 73.3, 63.5, 52.1, 33.2, 30.4,

27.8, 26.5, 25.5, 23.2, 18.9, -4.8; LRESIMS (m/e): 404.3 ([M+H]*); HRESIMS (m/e): calcd. for C24H42N02Si ([M+H]*) 404.2985, found 404.2981.

TPP-Ethyl Butyrate Complex IV-21

Following the general procedure (GP-2), desilylation of a Z/E mixture of 2,2,3,3-

Tetramethyl-12-propyl-4,10,13-trioxa-3-silapentadec-ll-ene IV-14 (40 mg, 0.12 mmol), followed by basic alumina chromatography (activity (II), ethyl acetate:hexane = 1:6 as eluant) gave 5-(2-ethoxypent-l-enyloxy)pentan-l-ol (15 mg, 58% yield).

The above alcohol was immediately employed in the esterification of 5-(4- carboxyphenyl)-10,15,20-triphenylporphyrin 111-22.(51 mg, 0.077 mmol) using EDC (21.5 mg, 0.112 mmol) as coupler, following the general procedure (GP-3). The crude mixture was concentratipurified by basic alumina chromatography (activity (II), CH2Cl2:hexane = 1:2 as eluant) to give IV-21-Z (16 mg), IV-21-E (27 mg) and a IV-21-Z/E mixture (8 mg). The combined yield of IV-21-Z/E in this reaction was 85%. rZ>Isomer IV-21-Z

R/(silica-CHîCh) 0.19; 'H-NMR (400 MHz, CôDe): ô = 8.96 (d, 2H, J = 4.8 Hz),

8.93 (s, 4H), 8.83 (d, 2H, J = 4.8 Hz), 8.49 (d, 2H, J = 8.2 Hz), 8.14-8.09 (m, 6H), 8.08 (d, 2H,

J = 8.2 Hz), 7.51-7.41 (m, 9H), 5.32 (s, IH, A^), 4.35 (t, 2H, J - 6.6 Hz), 4.19 (q, 2H, J = 7.0

Hz), 3.42 (t, 2H, J = 6.1 Hz), 1.94 (t, 2H, J = 7.2 Hz), 1.66-1.57 (m, 4H), 1.52-1.45 (m, 2H),

1.44-1.39 (m, 2H), 1.27 (t, 3H, J = 7.0 Hz), 0.93 (t, 3H, J = 7.4 Hz), -2.13 (s, 2H); '^C['H]

NMR (100 MHz, CeDe): ô = 166.9, 147.8, 143.1, 139.3 (A^ 135.3, 135.2, 132.0 (br., 13- carbons), 130.8, 128.5, 128.4 (A^), 128.2, 127.3, 121.4, 121.2, 119.6, 72.6, 66.4, 65.5, 34.1,

30.0, 29.3, 23.3, 21.4, 16.5, 14.1; LRESIMS (m/e): 857.4 ([M+H]*); HRESIMS (m/e): calcd. for C57H53N4O4 ([M+H]*) 857.4067, found 857.4069; UV-Vis (CH2CI2) UV-vis (CH2CI2)

Wnm(log e): 418 (5.75), 516 (4.24), 550 (3.92), 590 (3.79), 645 (3.69).

(£>Isomer IV-21-E

R/(silica-CH2Cl2) 0.31; 'H-NMR (400 MHz, CeDe): ô = 8.95 (d, 2H, J = 4.8 Hz),

8.92 (s, 4H), 8.82 (d, 2H, J = 4.8 Hz), 8.50 (d, 2H, J = 8.2 Hz), 8.13-8.10 (m, 6H), 8.07 (d, 2H,

J = 8.2 Hz), 7.51-7.45 (m, 9H), 5.76 (s, IH, A^), 4.39 (t, 2H, J = 6.6 Hz), 3.49 (t, 2H, J = 6.2

Hz), 3.42 (q, 2H, J = 7.0 Hz), 2.55 (t, 2H, J = 7.4 Hz), 1.81-1.73 (m, 2H), 1.71-1.64 (m, 2H),

1.62-1.55 (m, 2H), 1.53-1.45 (m, 2H), 1.12 (t, 3H, J = 6.9 Hz), 1.04 (t, 3H, J = 7.4 Hz), -2.15

(s, 2H); '^C['H] NMR (100 MHz, CôDe): ô = 166.9, 147.8, 147.7 (A\ 143.1, 135.2, 130.8,

128.7, 128.3, 127.3, 126.6 (A^), 121.4, 121.2, 119.6, 72.9, 65.5, 63.3, 30.9, 30.0, 29.4, 23.4,

21.3, 15.5, 14.5; ESIMS (m/e): 857.4 ([M+H]*); HRESIMS (m/e): calcd. for C57H53N4O4

([M+H]*) 857.4067, found 857.4069; UV-Vis (CH2CI2) Wnm(log e): 418 (5.78), 514 (4.32),

549 (4.01), 590 (3.88), 645 (3.79). Following the general procedure (GP-2), desilylation of (Z)-2,2,3,3-Tetramethyl -12- propyl-4,10,13-trioxa-3-silapentadec-ll-ene IV-14-Z (16 mg, 0.05 mmol), followed by basic

alumina chromatography (activity (II), ethyl acetate:hexane = 1:6 as eluant) gave fZ)-5-(2- ethoxypent-l-enyloxy)pentan-l-ol (7 mg, 62% yield).

The above alcohol was immediately employed in the esterification of ring B-BPD-7'^- monoacid 111-23 (23 mg, 0.033 mmol) using EDC (10 mg, 0.05 mmol) as coupler, following the general procedure (GP-3). The crude mixture was purified by prep. TLC (silica, 1%

MeOH in CH2CI2) to give IV-22-Z (16 mg, 53% yield).

'H-NMR (400 MHz, d6-acetone): ô = 9.88 (s, IH), 9.84 (s, IH), 9.56 (s, IH), 9.40 (s,

IH), 8.29 (dd, IH, J = 11.6 Hz, J = 17.9 Hz), 7.82 (d, IH, J = 5.7 Hz), 7.72 (d, IH, J = 5.7 Hz),

6.46 (dd, IH, J = 1.2 Hz, J = 17.9 Hz), 6.17 (dd, IH, J = 1.2 Hz, J = 11.6 Hz), 5.50 (s, IH, A^),

5.17 (s, IH), 4.37 (m, 2H), 4.24 (m, 2H), 4.14 (t, 2H, J = 7.6 Hz), 4.04 (q, 2H, J = 7.0 Hz),

3.74 (t, 2H, J = 6.3 Hz), 3.65 (s, 3H), 3.60 (s, 3H), 3.58 (s, 3H), 3.43 (s, 3H), 3.39 (s, 3H),

3.20 (t, 2H, J = 7.0 Hz), 3.16 (t, 2H, J = 7.4 Hz), 2.97 (s, 3H), 1.90-1.85 (m, 7H), 1.77 (m, 2H),

1.64 (m, 2H), 1.43 (m, 2H), 1.22 (t, 3H, J = 7.0 Hz), 0.87 (t, 3H, J = 7.4 Hz), -2.22 (s, 2H);

'^C['H] NMR (100 MHz, dg-acetone): ô = 173.9, 173.7, 171.1, 167.5, 166.9, 156.8, 154.8 (A\ 154.1, 152.9, 152.7, 141.6, 139.6, 138.6, 137.9, 137.7, 137.3, 135.2, 134.7, 134.5, 132.6,

131.8, 130.6, 129.2 (A"), 123.9, 121.4, 114.6, 101.0, 100.0, 94.6, 92.8, 72.9, 66.3, 65.6, 53.5,

51.9, 51.8, 51.6, 48.8, 37.5, 37.0, 33.9, 30.3, 29.5, 28.1, 23.5, 22.3, 21.9, 21.3, 16.3, 13.9, 12.6,

11.6, 11.2; LRESIMS (m/e): 917.5 ([M+H]*); HRESIMS (m/e): calcd. for C53H65N40,o

([M+H]*) 917.4701, found 917.4705; UV-Vis (CH2CI2) Wmn(log e): 433 (4.85), 581 (4.24),

629 (4.01), 690 (4.52).

TPP-Ethyl Benzoate Complex IV-23-Z

Following the general procedure (GP-2), desilylation of fZ;-2,2,3,3-tetramethyl -12- phenyl-4,10,13-trioxa-3-silapentadec-ll-ene IV-15-Z (16.4 mg, 0.045 mmol), followed by basic alumina chromatography (activity (II), ethyl acetate:hexane = 1:5 as eluant) gave (Z)-5-

(2-ethoxy-2-phenylvinyloxy)pentan-l-ol (7.8 mg, 70% yield).

The above alcohol was immediately employed in the esterification of 5-(4- carboxyphenyl)-10,15,20-triphenylporphyrin 111-22. (21 mg, 0.032 mmol) using EDC (10 mg,

0.05 mmol) as coupler, following the general procedure (GP-3). The crude mixture was purified by basic alumina chromatography (activity (II), CH2Cl2:hexane = 1:1 as eluant) to give IV-23-Z (27 mg, quantitative yield).

R/(silica-CH2Cl2) 0.22; 'H-NMR (400 MHz, CÔDS): Ô = 8.95 (d, 2H, J = 4.8 Hz), 8.92 (s, 4H), 8.82 (d, 2H, J = 4.7 Hz), 8.49 (d, 2H, J = 8.1 Hz), 8.13-8.09 (m, 6H), 8.08 (d, 2H,

J = 8.1 Hz), 7.53 (d, 2H, J = 7.3 Hz), 7.49-7.43 (m, 9H), 7.17-7.13 (m, 2H), 7.07-7.03 (m, IH),

6.16 (s, IH, A"), 4.35 (t, 2H, J = 6.5 Hz), 4.05 (q, 2H, J = 7.0 Hz), 3.49 (t, 2H, J = 6.1 Hz),

1.65-1.59 (m, 2H), 1.50-1.39 (m, 4H), 1.30 (t, 3H, J = 7.0 Hz), -2.14 (s, 2H); '^C['H] NMR

(100 MHz, CM: ô = 166.8, 147.8, 143.1, 139.1 (A^ not observed, inferred from the HMBC

correlation signal of the A*-proton), 136.9, 135.2, 134.2 (A^), 130.7, 129.0, 128.6, 128.2,

127.3, 125.0, 121.4, 121.2, 119.5, 73.1, 67.2, 65.4, 30.0, 29.2, 23.1, 16.2; LRESIMS (m/e):

891.4 ([M+H]*); HRESIMS (m/e): calcd. for C60H51N4O4 ([M+H]*) 891.3910, found

891.3909; UV-Vis (CH2CI2) Wnm(log e): 418 (5.58), 515 (4.12), 550 (3.81), 589 (3.68),

645 (3.58).

TPP- ô-valerolactone Complex IV-24

Ph

Following the general procedure (GP-2), desilylation of tert-butyldimethyl[5 -

[(tetrahydro-2H-pyran-2-ylidene)methoxy]pentyloxy]silane IV-16 (30.5 mg, 0.095 mmol), followed by basic alumina chromatography (activity (II), ethyl acetate:hexane = 1:4 as eluant) gave 5-[(tetrahydro-2H-pyran-2-ylidene)methoxy]pentan-l-ol (14 mg, 71% yield).

The above alcohol was immediately employed in the esterification of 5-(4- carboxyphenyl)-10,15,20-triphenylporphyrin 111-22. (46 mg, 0.07 mmol) using EDC (19 mg. 0.1 mmol) as coupler, following the general procedure (GP-3). The crude mixture was

concentrated and purified by basic alumina chromatography (activity (II), CH2Cl2:hexane =

1:1 as eluant) to give IV-24-Z (22.5 mg), IV-24-E (25 mg) and a IV-24-Z/E mixture (4.5 mg).

The combined yield of IV-24-Z/E in this reaction was 88%.

rZ>Isomer IV-24-Z

Rf (sihca-CH2Cl2) 0.09; 'H-NMR (400 MHz, d^-acetone): d = 8.86-8.85 (m, 8H),

8.45 (d, 2H, J = 8.0 Hz), 8.36 (d, 2H, J = 8.1 Hz), 8.25-8.22 (m, 6H), 7.84-7.78 (m, 9H), 5.47

(s, IH, A"), 4.50 (t, 2H, J = 6.5 Hz), 3.77-3.70 (m, 4H), 2.07-2.01 (m, 2H), 1.96-1.90 (m, 4H),

1.76-1.64 (m, 4H), 1.61-1.59 (m, 2H), -2.75 (s, 2H); '^C['H] NMR (100 MHz, do-acetone): ô

= 167.0, 147.6, 142.8, 137.5 (A^ not observed, inferred from the HMBC correlation signal of

the AVoton), 135.5, 135.3, 131.1, 129.0, 128.8 (A^), 127.8, 121.6, 121.4, 119.8, 72.5, 69.9,

65.9, 30.2, 29.5, 26.9, 26.7, 24.9, 23.4; LRESIMS (m/e): 841.3 ([M+H]*); HRESIMS (m/e):

calcd. for C56H49N4O4 ([M+H]*) 841.3754, found 841.3752; UV-Vis (CH2CI2) Wnm(log e):

418 (5.73), 514 (4.22), 550 (3.88), 590 (3.74), 645 (3.64).

r^^-Isomer IV-24-E

R/(silica-CH2Cl2) 0.19; 'H-NMR (400 MHz, CeDô): ô = 8.96 (d, 2H, J = 4.8 Hz),

8.93 (s, 4H), 8.83 (d, 2H, J = 4.8 Hz), 8.48 (d, 2H, J = 8.1 Hz), 8.14-8.06 (m, 8H), 7.51-7.41

(m, 9H), 6.32 (s, IH, A^), 4.33 (t, 2H, J = 6.5 Hz), 3.68-3.65 (m, 2H), 3.39 (t, 2H, J = 6.1 Hz),

2.48 (t, 2H, J = 6.0 Hz), 1.61-1.56 (m, 2H), 1.49-1.35 (m, 8H), -2.13 (s, 2H); '^C['H] NMR

(100 MHz, CéDé): ô = 166.9, 147.7, 143.1, 135.2, 133.1 (A^), 130.8, 128.6, 128.3, 127.3,

121.4, 121.2, 119.6, 72.5, 71.3, 65.5, 29.9, 29.3, 26.9, 24.0, 23.2; LRESIMS (m/e): 841.2

([M+H]*); UV-Vis (CH2CI2) Wnm(log e): 418 (5.35), 515 (3.90), 550 (3.59), 590 (3.46), TPP-Ibuprofen (methyl ester) Complex IV-25

Following the general procedure (GP-2), desilylation of 3-[l-(4-isobutylphenyl)ethyl]

-12,12,13,13-tetramethyl-2,5,ll-trioxa-12-silatetradec-3-ene IV-17 (55 mg, 0.127 mmol),

followed by basic alumina chromatography (activity (II), ethyl acetate:hexane = 1:4 as eluant)

gave 5-[3-(4-isobutylphenyl)-2-methoxybut-l -enyloxy]pentan-l-ol (30 mg, 75% yield).

Half of the above alcohol (the other half was employed in the synthesis of IV-26) was immediately employed in the esterification of 5-(4-carboxyphenyl)-10,15,20- triphenylporphyrin 111-22. (36 mg, 0.055 mmol) using EDC (15 mg, 0.08 mmol) as coupler, following the general procedure (GP-3). The crude mixture was concentrated and purified by silica prep. TLC (CH2CI2 as eluant) to give IV-25-Z (31 mg) and IV-25-E (14 mg). The combined yield of IV-25-Z/E in this reaction was quantitative.

(Z;-Isomer IV-25-Z

Rf (silica-CH2Cl2) 0.36; 'H-KMR (400 MHz, CeDe): ô = 8.96 (d, 2H, J = 4.8 Hz),

8.93 (s, 4H), 8.82 (d, 2H, J = 4.8 Hz), 8.48 (d, 2H, J = 8.1 Hz), 8.13-8.09 (m, 6H), 8.07 (d, 2H, J = 8.1 Hz), 7.49-7.43 (m, 9H), 7.35 (d, 2H, J = 8.0 Hz), 7.05 (d, 2H, J = 8.0 Hz), 5.47 (s, IH,

A*^), 4.34 (t, 2H, J = 6.5 Hz), 3.77 (s, 3H), 3.39-3.34 (m, 3H), 2.32 (d, 2H, J = 7.2 Hz), 1.76-

1.67 (m, IH), 1.63-1.56 (m, 2H), 1.46 (d, 3H, J = 7.1 Hz), 1.43-1.32 (m, 4H), 0.80 (d, 6H, J =

6.6 Hz), -2.14 (s, 2H); '^C['H] NMR (75 MHz, C^Df): ô = 166.9, 147.8, 144.7 (A\ 143.1,

142.8, 140.0, 135.3, 130.8, 129.7 (A^), 129.6, 128.6, 128.4, 128.3, 127.4, 121.4, 121.3,

119.672.7, 65.4, 59.9, 45.7, 42.4, 30.8, 30.0, 29.2, 23.2, 22.8, 19.8; LRESIMS (m/e): 983.7

([M+Na]*); HRESIMS (m/e): calcd. for C65H6oN404Na ([M+Na]*) 983.4512, found 983.4515;

UV-Vis (CH2CI2) Wnm(log e): 418 (5.60), 515 (4.14), 549 (3.84), 590 (3.71), 645 (3.62).

r£>Isomer IV-25-E

R/(silica-CH2Cl2) 0.51; 'H-NMR (400 MHz, CeDg): Ô = 8.95 (d, 2H, J = 4.8 Hz),

8.92 (s, 4H), 8.82 (d, 2H, J = 4.8 Hz), 8.50 (d, 2H, J = 8.1 Hz), 8.13-8.09 (m, 6H), 8.06 (d, 2H,

J = 8.0 Hz), 7.54 (d, 2H, J = 8.0 Hz), 7.49-7.44 (m, 9H), 7.07 (d, 2H, J = 8.0 Hz), 5.58 (s, IH,

A'), 4.60 (q, IH, J = 7.2 Hz), 4.39 (t, 2H, J = 6.5 Hz), 3.47 (t, 2H, J = 6.1 Hz), 3.12 (s, 3H),

2.27 (d, 2H, J = 7.2 Hz), 1.69-1.64 (m, IH), 1.65 (d, 3H, J = 7.3 Hz), 1.58-1.35 (m, 6H), 0.72

(d, 6H, J = 6.6 Hz), -2.15 (s, 2H); '^C['H] NMR (100 MHz, CÔDÔ): Ô = 166.8, 151.4 (A^),

147.8, 143.1, 142.9, 139.8, 135.2, 130.8, 129.6, 127.3, 124.7 (A*^), 121.4, 121.2, 119.6, 73.0,

65.5, 55.5, 45.6, 37.8, 30.8, 30.0, 29.4, 23.5, 22.8, 18.7; LRESIMS (m/e): 961.7 ([M+H]*);

HRESIMS (m/e): calcd. for C65H61N4O4 ([M+H]*) 961.4693, found 961.4692; UV-Vis

(CH2CI2) Wnm: 418, 514, 550, 591, 648. BPD-Ibuprofen (methyl ester) Complex IV-26

The second half of the alcohol 5-[3-(4-isobutylphenyl) -2-methoxybut-l-enyloxy]

pentan-l-ol generated during the synthesis of IV-25 was immediately employed in the

esterification of ring B-BPD-7^-monoacid 111-23 (39 mg, 0.055 mmol) using EDC (15 mg,

0.08 mmol) as coupler, following the general procedure (GP-3). The crude mixture was

concentrated and purified by silica prep. TLC (1% MeOH in CH2CI2 as eluant) to give IV-26-

Z (18 mg) and IV-26-E (11 mg). The combined yield of IV-26-Z/E in this reaction was 58%.

(Z;-Isomer IV-26-Z

R/(silica-l% MeOH in CH2CI2) 0.16; 'H-NMR (400 MHz, de-acetone): ô = 9.84 (s,

IH), 9.77 (s, IH), 9.51 (s, IH), 9.40 (s, IH), 8.28 (dd, IH, J = 11.6 Hz, J = 17.9 Hz), 7.82 (d,

IH, J = 5.7 Hz), 7.71 (d, IH, J = 5.7 Hz), 7.19 (d, 2H, J = 8.0 Hz), 7.02 (d, 2H, J = 8.0 Hz),

6.45 (dd, IH, J = 1.2 Hz, J = 17.9 Hz), 6.17 (dd, IH, J = 1.2 Hz, J = 11.6 Hz), 5.70 (s, IH, A^),

5.18 (s, IH), 4.43-4.32 (m, 2H), 4.18-4.09 (m, 2H), 4.10 (t, 2H, J = 7.6 Hz), 3.77 (t, 2H, J =

6.3 Hz), 3.65 (s, 3H), 3.62 (s, 3H), 3.60 (s, 3H), 3.57 (s, 3H), 3.34 (s, 3H), 3.32 (s, 3H), 3.35-

3.29 (m, IH), 3.16-3.12 (m, 4H), 2.98 (s, 3H), 2.36 (d, 2H, J = 7.2 Hz), 1.89-1.63 (m, lOH),

1.31 (d, 3H, J = 7.2 Hz), 0.80 (d, 6H, J = 6.8 Hz), -2.25 (s, 2H); '^C['H] NMR (100 MHz, de- acetone): ô = 173.9, 173.7, 171.1, 167.5, 166.8, 156.7, 154.1, 152.9, 152.7, 144.4 (A^ 143.0,

141.5, 140.0, 139.5, 138.6, 137.8, 137.6, 137.3, 135.1, 134.7, 134.4, 132.5, 131.8, 130.6,

130.3 (A'), 129.6, 128.1, 123.9, 121.3, 114.6, 100.9, 99.9, 94.6, 92.8, 73.1, 65.5, 59.7, 53.5,

51.8, 51.6, 48.8, 45.6, 42.1, 37.5, 37.0, 31.0, 30.0, 29.5, 28.1, 23.5, 22.6, 22.3, 21.8, 19.6, 12.5,

11.6, 11.1; LRESIMS (ni/e): 1021.3 ([M+Hf); HRESIMS (m/e): calcd. for C61H73N4O10

([M+H]*) 1021.5327, found 1021.5326; UV-Vis (CH2CI2) Wnm(log e): 432 (4.54), 581

(3.97), 629 (3.78), 690 (4.21).

r^V-Isomer IV-26-E

R/(silica-1% MeOH in CH2CI2) 0.26; 'H-NMR (400 MHz, CeDô): ô = 9.99 (s, IH),

9.74 (s, IH), 9.47 (s, IH), 9.21 (s, IH), 8.10 (dd, IH, J - 11.6 Hz, J = 17.9 Hz), 7.99 (d, IH, J

= 5.7 Hz), 7.56 (d, IH, J = 7.9 Hz), 7.20-7.10 (m, 2H), 6.42 (d, IH, J = 17.9 Hz), 6.03 (d, IH,

J = 11.5 Hz), 5.60 (s, IH, A^), 5.44 (s, IH), 4.60 (q, IH, J = 7.5 Hz), 4.43-4.20 (m, 2H), 4.22

(t, 2H, J - 7.4 Hz), 4.16 (t, 2H, J = 7.4 Hz), 3.49 (t, 2H, J = 6.2 Hz), 3.30 (s, 3H), 3.28 (s, 3H),

3.25 (s, 3H), 3.24 (s, 3H), 3.18-3.12 (m, 8H), 3.08 (t, 2H, J = 7.4 Hz), 2.67 (s, 3H), 2.36 (d,

2H, J = 7.2 Hz), 1.80-1.28 (m, 13H), 0.80 (d, 6H, J = 6.6 Hz), -1.73 (m, 2H); LRESIMS (m/e):

1021.3 ([M+H]*); UV-Vis (CH2CI2) Wnm(log e): 431 (4.53), 581 (3.96), 629 (3.70), 688

(4.26). TPP-Naproxen (methyl ester) Complex IV-27

Ph

P Ph-

Ph

19

Following the general procedure (GP-2), desilylation of (S)-3-[l-(6 -

methoxynaphthalen-2-yl)ethyl]-12,12,13,13-tetraniethyl-2,5,11 -trioxa-12-silatetradec-3-ene

IV-18 (37 mg, 0.08 mmol), followed by basic alumina chromatography (activity (II), ethyl

acetate-.hexane = 1:4 as eluant) gave (S;)-5-[2-methoxy-3-(6-methoxynaphthalen-2-yl)but-l -

enyloxy]pentan-l-ol (24 mg, 86% yield).

The above alcohol was immediately employed in the esterification of 5-(4-

carboxyphenyl)-10,15,20-triphenylporphyrin 111-22. (46 mg, 0.07 mmol) using EDC (23 mg,

0.12 mmol) as coupler, following the general procedure (GP-3). The crude mixture was purified by silica prep. TLC (CH2CI2 as eluant) to give IV-27-Z (34 mg) and IV-27-E (21 mg).

The combined yield of IV-27-Z/E in this reaction was 80%.

(Z;-Isomer IV-27-Z

R/(silica-CH2Cl2) 0.36; 'H-NMR (400 MHz, CeDe): ô = 8.95 (d, 2H, J = 4.8 Hz),

8.93 (s, 4H), 8.81 (d, 2H, J = 4.8 Hz), 8.48 (d, 2H, J = 8.1 Hz), 8.13-8.10 (m, 6H), 8.06 (d, 2H,

J = 8.1 Hz), 7.73 (s, IH), 7.64 (d, IH, J = 8.5 Hz), 7.57 (dd, IH, J = 1.6 Hz, J = 8.5 Hz), 7.53

(d, IH, J = 9.0 Hz), 7.48-7.42 (m, 9H), 7.16-7.12 (m, IH), 6.91 (d, IH, J = 2.3 Hz), 5.53 (s,

IH, A"), 4.35 (t, 2H, J = 6.5 Hz), 3.78 (s, 3H), 3.52 (q, IH, J = 7.1 Hz), 3.40 (t, 2H, J = 6.1 Hz), 3.31 (s, 3H), 1.63-1.58 (m, 2H), 1.55 (d, 3H, J = 7.1 Hz), 1.50-1.44 (m, 2H), 1.40-1.32

(m, 2H), -2.14 (s, 2H); '-C['H] NMR (100 MHz, CÔDÔ): Ô = 166. 9, 158.3, 147.8, 144.6 (A\

143.1, 140.3, 135.3, 134.4, 130.7, 130.1, 130.0 (A^), 128.7, 128.3, 127.7, 127.4, 127.3, 126.5,

121.4, 121.2, 119.6, 119.5, 106.3, 72.8, 65.4, 59.9, 55.1, 42.7, 30.0, 29.2, 23.2, 19.7;

LRESIMS (m/e): 985.5 ([M+H]*); HRESIMS (m/e): calcd. for C66H57N4O5 ([M+H]*)

985.4329, found 985.4332; UV-Vis (CH2CI2) Wnm(log e): 418 (5.86), 515 (4.41), 550

(4.09), 590 (3.96), 645 (3.86).

(E)-lsomer IV-27-E

R/(silica-CH2Cl2) 0.48; 'H-NMR (400 MHz, CÔDÔ): Ô = 8.93 (d, 2H, J = 5.0 Hz),

8.92 (s, 4H), 8.79 (d, 2H, J = 4.8 Hz), 8.48 (d, 2H, J = 8.0 Hz), 8.14-8.08 (m, 6H), 8.05 (d, 2H,

J = 7.9 Hz), 7.90 (s, IH), 7.78 (d, IH, J = 8.6 Hz), 7.67 (d, IH, J = 8.4 Hz), 7.56 (d, IH, J =

9.0 Hz), 7.51-7.43 (m, 9H), 7.08 (dd, IH, J = 2.3 Hz, J = 8.9 Hz), 6.85 (s, IH), 5.63 (s, IH,

A^), 4.71 (q, IH, J = 6.7 Hz), 4.38 (t, 2H, J = 6.0 Hz), 3.49 (t, 2H, J = 5.9 Hz), 3.19 (s, 3H),

3.16 (s, 3H), 1.72 (d, 3H, J = 7.2 Hz), 1.68-1.63 (m, 2H), 1.59-1.53 (m, 2H), 1.52-1.47 (m,

2H), -2.16 (s, 2H); LRESIMS (m/e): 985.5 ([M+H]*); HRESIMS (m/e): calcd. for

C66H57N4O5 ([M+H]*) 985.4329, found 985.4338; UV-Vis (CH2CI2) Wnm: 418, 515, 549,

590, 647. BPD-Naproxen (methyl ester) Complex IV-28

Following the general procedure (GP-2), desilylation of (S)-3-[l-(6 -

methoxynaphthalen-2-yl)ethyl]-12,12,13,13-tetramethyl-2,5,11 -trioxa-12-silatetradec-3-ene

IV-18 (37 mg, 0.08 mmol), followed by basic alumina chromatography (activity (II), ethyl

acetate:hexane = 1:4 as eluant) gave (5;)-5-[2-methoxy-3-(6-methoxynaphthalen-2-yl)but-l -

enyloxy]pentan-l-ol (23 mg, 82% yield).

The above alcohol was immediately employed in the esterification of ring B-BPD-7'^- monoacid 111-23 (39 mg, 0.055 mmol) using EDC (23 mg, 0.12 mmol) as coupler, following the general procedure (GP-3). The crude mixture was purified by silica prep. TLC (CH2CI2 as eluant) to give IV-28-Z (19 mg) and IV-28-E (14 mg). The combined yield of IV-28-Z/E in this reaction was 58%.

fZ^Isomer IV-28-Z (a pair of diastereomers at ratio of 1:1)

Rf (sihca-CH2Cl2) 0.08; 'H-NMR (300 MHz, CeD^, peaks of the diastereomers are essentially coincident with each other and for each diastereomer, one proton was integrated as

0.5H): Ô = 9.95 (s, IH), 9.73 (s, IH), 9.47 (s, IH), 9.17 (s, IH), 8.09 (dd, IH, J = 11.6 Hz, J =

17.8 Hz), 7.98 (d, IH, J = 5.7 Hz), 7.75 (s, IH), 7.66 (d, IH, J = 8.4 Hz), 7.59 (d, IH, J = 8.3 Hz), 7.56 (d, IH, J = 8.9 Hz), 7.18-7.12 (m, 2H), 6.92 (s, IH), 6.41 (dd, IH, J = 1.4 Hz, J =

17.8 Hz), 6.02 (dd, IH, J = 1.4 Hz, J = 11.6 Hz), 5.55 (s, IH, A^), 5.44 (s, IH), 4.40-4.20 (m,

2H), 4.21 (t, 2H, J = 7.5 Hz), 4.13-4.05 (m, 2H), 3.80 (s, 3H), 3.54 (q, IH, J = 7.2 Hz), 3.42 (t,

2H, J = 6.3 Hz), 3.31 (s, 3x0.5H), 3.30 (s, 3x0.5H), 3.29 (s, 3H), 3.28 (s, 3H), 3.24 (s, 3H),

3.23 (s, 3H), 3.16 (t, 2H, J = 7.3 Hz), 3.04 (t, 2H, J = 7.2 Hz), 3.02 (s, 3H), 2.68 (s, 3H), 1.70

(s, 3H), 1.56 (d, 3H, J = 7.1 Hz), 1.65-1.15 (m, 6H), -1.75 to -1.9(m, 2H); ESIMS (m/e):

1045.3 ([M+H]*); UV-Vis (CH2CI2) Wnm: 353, 430, 581, 630, 690

(E)-lsomer IV-28-E (a pair of diastereomers at ratio of 1:1)

R/(silica-CH2Cl2) 0.13; 'H-NMR (300 MHz, CeDe, peaks of the diastereomers are

essentially coincident with each other and for each diastereomer, one proton was integrated as

0.5H): ô = 9.95 (s, IH), 9.72 (s, IH), 9.47 (s, IH), 9.16 (s, 0.5H), 9.15 (s, 0.5H), 8.09 (dd,

0.5H, J = 11.5Hz, J = 17.7Hz), 8.08 (dd, 0.5H, J = 11.5Hz, J = 17.7Hz), 7.99 (d, IH, J =

5.8Hz), 7.95 (s, IH), 7.83 (tt, IH, J = 2.1Hz, J = 8.5Hz), 7.72 (dd, IH, J = 1.8Hz, J = 8.5Hz),

7.63 (d, IH, J = 8.9Hz), 7.19-7.16 (m, IH), 7.12 (d, IH, J = 5.6Hz), 6.92 (m, IH), 6.41 (d, IH,

J = 17.7Hz), 6.02 (d, IH, J = 11.5Hz), 5.65 (s, IH, A^), 5.46 (s, IH), 4.76 (q, 0.5H, J = 7.2Hz),

4.75 (q, 0.5H, J = 7.2Hz), 4.41-4.23 (m, 2H), 4.21 (t, 2H, J = 7.4Hz), 4.12-4.03 (m, 2H), 3.51

(t, 2H, J = 6.1Hz), 3.28 (s, 6H), 3.27 (s, 3x0.5H), 3.25 (s, 3H), 3.24 (s, 3x0.5H), 3.23 (s, 3H),

3.17 (s, 3x0.5H), 3.16 (s, 3x0.5H), 3.15 (t, 2H, J - 7.3Hz), 3.03 (t, 2H, J = 7.5Hz), 3.00 (s,

3H), 2.70 (s, 3H), 1.77 (d, 3x0.5H, J = 7.3Hz), 1.76 (d, 3x0.5H, J = 7.3Hz), 1.71 (s, 3H), 1.68-

1.43 (m, 6H), -1.70 to -1.79 (m, 2H); LRESIMS (m/e): 1045.4 ([M+H]*); HRESIMS (m/e): calcd. for C62H69N40n ([M+H]*) 1045.4963, found 1045.4983; UV-Vis (CH2CI2)

Wnm(log e): 431 (5.01), 581 (4.24), 630 (3.97), 690 (4.71). TPP- (N-methylbenzanilide) Complex IV-29

Ph

Following the general procedure (GP-2), desilylation of N-[2-[5-(tert- butyldimethylsilyloxy)pentyloxy]-l-phenylvinyl]-N-methylaniline IV-19 (33 mg, 0.076 mmol), followed by basic alumina chromatography (activity (II), ethyl acetaterhexane =1:4 as eluant) gave 5-[2-(methylphenylamino)-2-phenylvinyloxy]pentan-l -ol (15 mg, 64% yield).

The above alcohol was immediately employed in the esterification of 5-(4- carboxyphenyl)-10,15,20-triphenylporphyrin 111-22. (33 mg, 0.05 mmol) using EDC (14 mg,

0.075 mmol) as coupler, following the general procedure (GP-3). The crude mixture was purified by basic alumina chromatography (activity (II), CHaCli.'hexane = 1:2 as eluant) to give a IV-29-Z/E mixture (37.5 mg, 81% yield, Z:E = 4:1).

fZ^Isomer IV-29-Z (not isolated, data were obtained irom the above mixture sample)

R/ (silica-CHaCb) 0.65; 'H-NMR (400 MHz, C^De, extracted from the spectrum of the above Z/E mixture): Ô = 8.96 (d, 2H, J = 4.8 Hz), 8.93 (s, 4H), 8.83 (d, 2H, J = 4.8 Hz),

8.49 (d, 2H, J = 8.3 Hz), 8.14-8.06 (m, 8H), 7.49-7.41 (m, 9H), 7.33 (d, 2H, J = 7.2 Hz), 7.25-

7.20 (m, 2H), 7.14-7.08 (m, 2H), 7.06-7.00 (m, IH), 6.86 (d, 2H, J = 7.9 Hz), 6.82-6.76 (m,

IH), 6.30 (s, IH, A^), 4.30 (t, 2H, J = 6.6 Hz), 3.37 (t, 2H, J = 6.1 Hz), 3.05 (s, 3H), 1.54-1.47 (m, 2H), 1.39-1.17 (m, 4H), -2.13 (s, 2H); '^C['H] NMR (100 MHz, C(J)6, extracted from the

spectrum of the above Z/E mixture): ô = 166.9, 149.3, 147.8, 143.1 (A*'), 137.9, 135.3, 130.8,

129.6, 129.3, 128.8, 128.3, 127.4, 127.3, 126.7 (A^), 125.6, 121.5, 121.3, 119.6, 117.6, 113.8,

73.1, 65.5, 38.2, 30.1, 29.1, 22.9; LRESIMS (m/e, resuk of the mixture sample): 952.4

([M+H]*); HRESIMS (m/e, result of the mixture sample): calcd. for C65H54N5O5 ([M+H]*)

952.4227, found 952.4224; UV-Vis (CH2CI2, result of the mixture sample) Wnm(log e):

418 (5.63), 515 (4.17), 550 (3.84), 589 (3.71), 645 (3.61).

f£>Isomer IV-29-E (not isolated, data were obtained from the above mixture sample)

'H-NMR (400 MHz, CtyDe, exfracted from the spectrum of the above Z/E mixture): ô

= 8.97-8.93 (m, 6H), 8.82 (d, 2H, J = 4.8 Hz), 8.49 (m, 2H), 8.14-8.06 (m, 8H), 7.90 (dd, IH,

J = 1.1 Hz, J = 8.5 Hz), 7.49-7.41 (m, 9H), 7.25-7.20 (m, 4H), 7.06-7.00 (m, IH), 6.91 (dd,

2H, J = 1.0 Hz, J = 8.8 Hz), 6.82-6.76 (m, IH), 6.27 (s, IH, A^), 4.29 (m, 2H), 3.35 (m, 2H),

2.96 (s, 3H), 1.54-1.47 (m, 2H), 1.39-1.12 (m, 4H), -2.13 (s, 2H).

5.4.2 Photooxygenation

Determination of the Relative GC Response Factor

Based on Equation 3.1 of section 3.4.1, the relative GC response factors of ethyl butyrate and ethyl benzoate were determined (Table 5.2). Ibuprofen methyl I Naproxen methyl I ô-Valerolactone [ N-methylbenzanilide | ester IV-12 ' esters IV-13

A i A Program ; I î TR^min)^1.78 ; ' 1527 | i Avg GC : Mof ' Avg GC^ [ Mol " r Avg GC r r p^gQQ i Ratio ; Ratio Ratio j Ratio j Ratio ! Ratio I Ratio | Ratio Entries 1.872 7 0^10 : Til ^435- | 0668 r 0331 r YA96 \ '~ 3 45 r 0L468 ' i Ô.Î96 ^ ; 0J28 1 Ï.11 i r 0936~ 1^^^^^ p j^^^^ p 2^672:X4J5'-'' jo7748 ^ " i"1.95^

5.4.2.1 Photooxygenation of TPP-Ethyl Butyrate Complex IV-21-Z

In CéDé

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate

complex IV-21-Z (ca. 3.5 mg, 4 /tmol) and 1,3,5-trimethoxybenzene (ca. 0.7 mg, 4 ixmoY)

were dissolved in 0.5 mL C^D^ with an NMR-determined molar ratio of 1.12 (IV-21-

Z/interaal standard). Photoirradiation of the reaction solution for 4 min yielded dioxetane IV-

32-Z (22%), aldehyde IV-30 (65%) and ethyl butyrate (71%). The GC yield of total releasable

ethyl butyrate was 94%..

In CDCI3

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate

complex IV-21-Z (ca. 1.4 mg, 1.6 jumol) and 1,3,5-trimethoxybenzene (ca. 0.5 mg, 3 /xmol)

were dissolved in 0.5 mL CDCI3 with an NMR-determined molar ratio of 0.42 (IV-21- Z/intemal standard). Photoirradiation of the reaction solution for 3 min yielded dioxetane IV-

32-Z (70%), aldehyde IV-30 (17%) and ethyl butyrate (21%). The GC yield of total releasable ethyl butyrate was quantitative. Attempt to isolate IV-32-Z was unsuccessful as it decomposed on sihca gel PTLC (CH2CI2 as eluant). However, pure IV-30 was obtained.

Aldehyde IV-30

Ph

R/(silica-CH2Cl2) 0.26; ^H-NMR (300 MHz, CDCI3): ô = 8.86-8.84 (m, 6H), 8.78 (d,

2H, J = 4.7 Hz), 8.42 (d, 2H, J = 7.8 Hz), 8.30 (d, 2H, J = 7.8 Hz), 8.22-8.19 (m, 6H), 8.10 (s,

IH, C**), 7.78-7.70 (m, 9H), 4.52 (t, 2H, J = 6.6 Hz), 4.26 (t, 2H, J = 6.4 Hz), 1.97-1.85 (m,

2H), 1.83-1.72 (m, 2H), 1.70-1.62 (m, 2H), -2.79 (s, 2H); LRESIMS (m/e): 773.3 ([M+H]*);

HRESIMS (m/e): calcd. for C51H41N4O4 ([M+H]*) 773.3128, found 773.3131.

Dioxetane IV-32-Z (not isolated, data were obtained from a mixture sample)

R/(silica-CH2Cl2) 0.37; "H-NMR (300 MHz, CDCI3, peaks were extracted from the spectmm of the crude photooxygenation mixture): ô = 8.85-8.83 (m, 6H), 8.77 (d, 2H, J = 4.8

Hz), 8.42 (d, 2H, J = 8.1 Hz), 8.29 (d, 2H, J = 8.1 Hz), 8.22-8.19 (m, 6H), 7.78-7.70 (m, 9H),

5.86 (s, IH, B*'), 4.51 (t, 2H, J = 6.4 Hz), 4.35-4.28 (m, 2H), 3.80-3.62 (m, 2H), 1.95-1.65 (m,

8H), 1.52-1.48 (m, 2H), 1.25 (t, 2H, J = 7.1 Hz), 0.94 (t, 2H, J = 7.4 Hz), -2.80 (s, 2H);

LRESIMS (m/e, resuit of the mixture sample): 889.1 ([M+H]*); HRESIMS (m/e, resuit of the

mixture sample): calcd. for C57H53N4O6 ([M+H]*) 889.3965, found 889.3966.

In CDClarMeOD = 4:1 mixed solvent

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate

complex IV-21-Z (ca. 1.6 mg, 1.8 /mol) and 1,3,5-trimethoxybenzene (ca. 0.5 mg, 3 /anol)

were dissolved in 0.5 mL CDCfvMeOD = 4:1 mixed solvent with an NMR-determined molar

ratio of 0.55 (IV-21-Z/intemal standard). Photoirradiation of the reaction solution for 3 min

yielded dioxetane IV-32-Z (73%), aldehyde IV-30 (20%) and ethyl butyrate (17%). The GC yield of total releasable ethyl butyrate was quantitative.

In de-acetone

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate complex IV-21-Z (ca. 2 mg, 2.2 /anol) and 1,3,5-trimethoxybenzene (ca. 0.3 mg, 2 /xmol) were dissolved in 0.5 mL de-acetone with an NMR-determined molar ratio of 1.20 (IV-21-

Z/intemal standard). Photoirradiation of the reaction solution for 8 min yielded dioxetane IV-

32-Z (38%), aldehyde IV-30 (61%) and ethyl butyrate (56%). The GC yield of total releasable ethyl butyrate was quantitative. Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate

complex IV-21-Z {ca. 2 mg, 2.2 jumol) and 1,3,5-trimethoxybenzene {ca. 0.7 mg, 4 /unol)

were dissolved in 0.5 mL de-acetone with an NMR-determined molar ratio of 0.42 (IV-21-

Z/intemal standard). l,4-diazabicyclo[2.2.2]octane (DABCO, 1.5 mg, 13.4 mmol) was added

to the reaction solution before it was illuminated for 1 h to yield aldehyde IV-30 (100%) and

ethyl butyrate (100%). The GC yield of total releasable ethyl butyrate was quantitative.

5.4.2.2 Photooxygenation of BPD-Ethyl Butyrate Complex IV-22-Z

Following the general photooxygenation procedure (GP-4), BPD-Ethyl Butyrate

complex IV-22-Z (ca. 2.3 mg, 2.5 /miol) and 1,3,5-trimethoxybenzene {ca. 0.5 mg, 3 /anol)

were dissolved in 0.5 mL mixed solvent of CeDe ide-acetone = 5:1, with an NMR-detennined

molar ratio of 0.76 (IV-22-Z/intemal standard). Photoirradiation of the reaction solution for 5

min yielded dioxetane IV-33-Z (84%), aldehyde IV-31 (6%) and ethyl butyrate (6%). The GC

yield of total releasable ethyl butyrate was 85%.

Dioxetane IV-33-Z (not isolated, data were obtained from a mixture sample) 'H-NMR (400 MHz, CôDô rd^-acetone = 5:1, peaks were extracted from the

spectrum of the crude photooxygenation mixture): ô = 9.87 (s, IH), 9.75 (s, IH), 9.34 (s, IH),

9.33 (s, IH), 8.10 (dd, IH, J = 11.6 Hz, J = 17.7 Hz), 7.81 (d, IH, J = 5.7 Hz), 7.36 (d, IH, J =

5.9 Hz), 6.33 (d, IH, J = 17.9 Hz), 6.00 (d, IH, J = 11.6 Hz), 5.79 (s, IH, B^), 5.21 (s, IH),

4.47-4.34 (m, 2H), 4.28-4.15 (m, 2H), 4.17 (t, 2H, J = 7.5 Hz), 4.11 (t, 2H, J = 7.5 Hz), 3.54-

3.47 (m, 2H), 3.41 (s, 3H), 3.37 (s, 3H), 3.36 (s, 3H), 3.25 (s, 6H), 3.08 (t, 4H, J = 7.6 Hz),

2.70 (s, 3H), 1.81-1.37 (m, lOH), 1.70 (s, 3H), 1.17 (t, 3H, J = 7.1 Hz), 0.81 (t, 3H, J = 7.4

Hz), -2.03 (s, 2H); LRESIMS (m/e, result of the mixture sample): 949.5 ([M+H]*); HRESIMS

(m/e, result of the mixture sample): calcd. for C53H65N4O12 ([M+H]*) 949.4599, found

949.4604.

5.4.2.3 Photooxygenation ofTPP-Ethyl Butyrate Complex IV-21-E

In CéDft

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate complex IV-21-E (ca. 7 mg, 8 /tmol) and 1,3,5-trimethoxybenzene (ca. 1.3 mg, 8 /anol) were dissolved in 0.5 mL CÔDÔ with an NMR-determined molar ratio of 0.96 (IV-21-E/intemal standard). Photo irradiation of the reaction solution for 30 min yielded hydroperoxide IV-34-Z

(34%), hydroperoxide IV-34-E (21%), aldehyde IV-30 (25%) and ethyl butyrate (25%). The

GC yield of total releasable ethyl butyrate was 32%.

In CDCI3

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate complex IV-21-E {ca. 0.85 mg, 1 /miol) and 1,3,5-triniethoxybenzene (ca. 0.3 mg, 2 frniol) were dissolved in 0.5 mL CDCI3 with an NMR-determined molar ratio of 0.55 (IV-21-

E/intemal standard). Photoirradiation of the reaction solution for 1 min yielded hydroperoxide

IV-34-Z (29%), hydroperoxide IV-34-E (27%) and dioxetane IV-32-E (37%). The GC yield of total releasable ethyl butyrate was 33%.

In CDCbrMeOD = 4:1 mixed solvent

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate complex IV-21-E {ca. 0.9 mg, 1 /mol) and 1,3,5-trimethoxybenzene {ca. 0.3 mg, 2 /tmol) were dissolved in 0.5 mL mixed solvent of CDClarMeOD = 4:1, with an NMR-determined molar ratio of 0.61 (IV-21-E/intemal standard). Photoirradiation of the reaction solution for

1.5 min yielded hydroperoxide IV-34-Z (31%), hydroperoxide IV-34-E (30%) and dioxetane

IV-32-E (39%). The GC yield of total releasable ethyl butyrate was 26%.

In do-acetone

Following the general photooxygenation procedure (GP-4), TPP-Ethyl Butyrate complex IV-21-E {ca. 0.85 mg, 1 /tmol) and 1,3,5-trimethoxybenzene {ca. 0.2 mg, 1 /mol) were dissolved in 0.5 mL de-acetone with an NMR-determined molar ratio of 0.81 (IV-21-

E/intemal standard). Photoirradiation of the reaction solution for 2.5 min yielded hydroperoxide IV-34-Z (42%), hydroperoxide IV-34-E (30%) and aldehyde IV-30 (17%). The

GC yield of total releasable ethyl butyrate was 30%>. Following the general photooxygenation procedure (GP-4), TPP-Ethyl Benzoate

complex IV-23-Z (ca. 3.2 mg, 3.6 /anol) and 1,3,5-trimethoxybenzene (ca. 1.3 mg, 8 /imol)

were dissolved in 0.5 mL CeDe with an NMR-determined molar ratio of 0.50 (IV-23-

2[/intemal standard). Photoirradiation of the reaction solution for 2 min yielded dioxetane IV-

35-Z (64%), aldehyde IV-30 (36%) and ethyl benzoate (20%). The GC yield of total releasable ethyl benzoate was 72%.

Dioxetane IV-35-Z (not isolated, data were obtained from a mixture sample)

H-NMR (400 MHz, CtiD^, peaks were extracted from the spectrum of the crude photooxygenation mixture): Ô = 8.95 (d, 2H, J = 4.8 Hz), 8.92 (s, 4H), 8.82 (d, 2H, J = 4.7 Hz),

8.49 (d, 2H, J = 8.1 Hz), 8.13-8.04 (m, 8H), 7.89 (d, 2H, J = 7.2 Hz), 7.49-7.43 (m, 9H), 7.17-

7.03 (m, 3H), 5.85 (s, IH, B*), 4.54-4.31 (m, 2H), 4.33 (t, 2H, J = 6.5 Hz), 3.36-3.17 (m, 2H),

1.56 (ra, 2H), 1.38-1.33 (m, 4H), 1.27 (t, 3H, J = 7.0 Hz), -2.14 (s, 2H); ESMS (m/e, result of the mixture sample): 923.1 ([M+H]*). Following the general photooxygenation procedure (GP-4), TPP- ô-valerolactone

complex IV-24-Z (ca. 4.2 mg, 5 /miol) and 1,3,5-trimethoxybenzene (ca. 0.6 mg, 4 /lanol) were dissolved in 0.5 mL do-acetone with an NMR-determined molar ratio of 1.22 (IV-24-

Z/intemal standard). Photoirradiation of the reaction solution for 3 min yielded dioxetane IV-

36-Z (35%), aldehyde IV-30 (46%) and ô-valerolactone (59%). The GC yield of total releasable ô-valerolactone was 90%).

Dioxetane IV-36-Z (not isolated, data were obtained from a mixture sample)

' H-NMR (400 MHz, de-acetone, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.88 (m, 8H), 8.47 (d, 2H, J = 8.0 Hz), 8.38 (d, 2H, J =

8.1 Hz), 8.27-8.24 (m, 6H), 7.86-7.80 (m, 9H), 5.84 (s, IH, B"), 4.52 (t, 2H, J = 6.5 Hz), 3.97-

3.81 (m, 4H), 2.02-1.67 (m, 12H), -2.74 (s, 2H); LRESIMS (m/e, resuit of the mixture sample): 873.5 ([M+H]*); HRESIMS (m/e, resuit of the mixture sample): calcd. for

C56H49N4O6 ([M+H]*) 873.3652, found 873.3654. Following the general photooxygenation procedure (GP-4), TPP-(N- methylbenzanilide) complex IV-29 (ca. 3.6 mg, 3.8 |Umol, Z:E = 4:1) and 1,3,5- trimethoxybenzene (ca. 1.2 mg, 8 /imol) were dissolved in 0.5 mL C^Df, with an NMR- determined molar ratio of 0.42 (IV-29/intemal standard). Photoirradiation of the reaction solution for 5 min yielded aldehyde IV-30 (96%) and N-methylbenzanilide (96%). The GC yield of total releasable N-methylbenzanihde was 88%.

5.4.2.7 Photooxygenation of TPP-Ibuprofen (methyl ester) Complex IV-25-Z

Following the general photooxygenation procedure (GP-4), TPP-Ibuprofen (methyl ester) Complex IV-25-Z (ca. 7.2 mg, 7.5 jumol) and 1,3,5-trimethoxybenzene (ca. 2.7 mg, 16

/tmol) were dissolved in 0.5 mL CeDe with an NMR-determined molar ratio of 0.46 (IV-25-

Z/rntemal standard). Photoirradiation of the reaction solution for 2.5 min yielded dioxetane IV-

38-Z (69%), aldehyde IV-30 (23%) and ibuprofen methyl ester (20%). The GC yield of total releasable ibuprofen methyl ester was quantitative.

Dioxetane IV-38-Z-XA' (2 pairs of enantiomers showed 2 sets of'H-NMR signals at 1:1 ratio)

Ph

Ph

,14

B,1 5 'H-NMR (400 MHz, CôDe, for each set, every proton was integrated as 0.5H. All

peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.96-

8.95 (m, 2H), 8.93 (s, 4H), 8.84-8.81 (m, 2H), 8.50 (d, 2H, J = 8.1 Hz), 8.13-8.06 (m, 8H),

7.49-7.43 (m, 9H), 7.42-7.40 (m, 2H), 7.01 (d, 2H, J = 8.0 Hz), 5.77 (s, 0.5H, B'-X), 5.74 (s,

0.5H, B'-Y), 4.32 (t, 2H, J = 6.5 Hz), 4.11 (s, 3x0.5H, B''-X), ), 4.02 (s, 3x0.5H, B"-Y), 3.54-

3.12 (m, 2H), 3.08-3.00 (m, 0.5H), 2.88-2.80 (m, 0.5H), 2.35 (d, 2x0.5H, J = 7.2 Hz, B'^-X),

2.29 (d, 2x0.5H, J = 7.2 Hz, B'^-Y), 1.78-1.29 (m, 7H), 1.36 (d, 3H, J = 7.2 Hz, B'^-XTT),

0.82 (d, 6x0.5H, J = 6.4 Hz, B'^-X), 0.77 (d, 6x0.5H, J = 6.6 Hz, B'^-Y), -2.14 (s, 2H);

LRESIMS (m/e, resuit of the mixture sample): 993.1 ([M+H]*); HRESIMS (m/e, resuit of the mixture sample): calcd. for C65H61N4O6 ([M+H]*) 993.4591, found 993.4594.

5.4.2.8 Photooxygenation of BPD-Ibuprofen (methyl ester) Complex IV-26-Z

Following the general photooxygenation procedure (GP-4), BPD-Ibuprofen (methyl ester) Complex IV-26-Z (ca. 2 mg, 2 /unol) and 1,3,5-trimethoxybenzene (ca. 0.5 mg, 3 /rniol) were dissolved in 0.5 mL CÔDÔ with an NMR-determined molar ratio of 0.60 (IV-26-

Z/intemal standard). Photoirradiation of the reaction solution for 6 min yielded dioxetane IV-

39-Z (85%), aldehyde IV-31 (5%) and ibuprofen methyl ester (9%). The GC yield of total releasable ibuprofen methyl ester was quantitative. Dioxetane IV-SQ-Z-X/Y (not isolated, data were obtained from a mixture sample)

LRESIMS (m/e, result of the crude photooxygenation mixture): 1053.2 ([M+H]*);

HRESIMS (m/e, result of the crude photooxygenation mixture): calcd. for C61H73N4O12

([M+H]*) 1053.5225, found 1053.5228.

5.4.2.9 Photooxygenation of TPP-Naproxen (methyl ester) Complex IV-27-Z

Following the general photooxygenation procedure (GP-4), TPP-Naproxen (methyl ester) Complex IV-27-Z (ca. 3.7 mg, 3.8 /anol) and 1,3,5-trimethoxybenzene (ca. 0.8 mg, 4.5

/unol) were dissolved in 0.5 mL CeDô with an NMR-determined molar ratio of 0.85 (iV-27-

Z/intemal standard). Photoirradiation of the reaction solution for 7 min yielded dioxetane IV-

40-Z (12%), aldehyde IV-30 (76%) and naproxen methyl ester (76%). The GC yield of total releasable naproxen methyl ester was 66%. Dioxetane IV-40-Z (not isolated, data were obtained from a mixture sample)

Ph

,o Ph-\ o

Ph

16

,14 o— B,1 9

LRESIMS (m/e, result of the crude photooxygenation mixture): 1017.0 ([M+H]*);

HRESIMS (m/e, result of the crude photooxygenation mixture): calcd. for C66H57N4O7

([M+H]*) 1017.4227, found 1017.4225.

5,4.2.10 Pliotooxygenation of BPD-Naproxen (methyl ester) Complex IV-28-Z

Following the general photooxygenation procedure (GP-4), BPD-Naproxen (methyl ester) Complex IV-28-Z (ca. 3.7 mg, 3.6 /xmol) and 1,3,5-trimethoxybenzene (ca. 0.7 mg, 4 jUmol) were dissolved in 0.5 mL CeDe with an NMR-determined molar ratio of 0.82 (IV-28-

Z/intemal standard). Photoirradiation of the reaction solution for 3 min yielded dioxetane IV-

41 -Z (27%) and naproxen methyl ester (70%). The GC yield of total releasable naproxen methyl ester was 57%. LRESIMS (m/e, result of the crude photooxygenation mixture): 1077.2 ([M+H]*);

HRESIMS (m/e, result of the crude photooxygenation mixture): calcd. for C62H69N4O13

([M+H]*) 1077.4861, found 1077.4874.

5.4.2.11 Pliotooxygenation of TPP-(ô-Valerolactone) Complex IV-24-E

Following the general photooxygenation procedure (GP-4), TPP-(ô-valerolactone) complex IV-24-E (ca. 0.5 mg, 0.6 /unol) and 1,3,5-trimethoxybenzene (ca. 0.4 mg, 2.5 /anol) were dissolved in 0.5 mL CÔDÔ with an NMR-determined molar ratio of 0.23 (IV-24-

E/intemal standard). Photo irradiation of the reaction solution for 1.5 min yielded hydroperoxide IV-42-Z (86%). The GC yield of total releasable 5-valerolactone was 4%. Hydroperoxide IV-41 -Z (not isolated, data were obtained from a mixture sample)

B9 B^O

H-NMR (400 MHz, CeDe, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.95 (d, 2H, J = 4.8 Hz), 8.92 (s, 4H), 8.82 (d, 2H, J = 4.8 Hz),

8.47 (d, 2H, J = 8.1 Hz), 8.13-8.06 (m, 8H), 7.50-7.41 (m, 9H), 5.27 (t, IH, J = 4 Hz, B\

5.23 (s, IH, B^), 4.37 (t, 2H, J = 6.5 Hz), 3.76-3.74 (m, IH), 3.71-3.68 (m, 2H), 3.44-3.41 (m,

IH), 1.76-1.33 (m, lOH), -2.15 (s, 2H); LRESIMS (m/e, result of the mixture sample): 873.5

([M+H]*); HRESIMS (m/e, result of the mixture sample): calcd. for C56H49N4O6 ([M+H]*)

873.3652, found 873.3653.

5.4.2.12 Photooxygenation of TPP-Ibuprofen (methyl ester) Complex IV-25-E

Following the general photooxygenation procedure (GP-4), TPP-Ibuprofen (methyl ester) Complex IV-25-E (ca. 5.4 mg, 5.6 /anol) and 1,3,5-trimethoxybenzene (ca. 0.8 mg, 5

/anol) were dissolved in 0.5 mL CôDewith an NMR-determined molar ratio of 1.17 (IV-25-

E/intemal standard). Photoirradiation of the reaction solution at 5 °C for 14 min yielded hydroperoxide IV-43-Z (61%). The GC yield of total releasable ibuprofen methyl ester was

30%. ' H-NMR (400 MHz, C^D^, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 8.95 (d, 2H, J = 4.8 Hz), 8.92 (s, 4H), 8.82 (d, 2H, J = 4.8 Hz),

8.48 (d, 2H, J = 8.1 Hz), 8.13-8.06 (m, 8H), 7.49-7.44 (m, 9H), 7.35 (d, 2H, J - 8.0 Hz, B"^),

7.04 (d, 2H, J = 8.0 Hz, B"), 5.59 (s, IH, B"), 4.36 (m, 2H), 3.80 (s, 3H, B"), 3.52-3.34 (m,

2H), 2.34 (d, 2H, J = 7.2 Hz, B'\ 2.11 (s, 3H, B"'), 1.79-1.31 (m, 8H), 0.82 (d, 6H, J = 6.8

Hz, B'^), -2.15 (s, 2H); '^C['H] NMR (100 MHz, CeDe, peaks were extracted from the spectrum of the crude photooxygenation mixture): ô = 167.0, 147.8, 147.0 (B^), 143.1, 141.3,

138.6, 135.2, 130.8, 129.7, 129.1, 128.0, 127.7 (B^ 127.3, 121.4, 121.2, 119.6, 106.0 (B^),

69.3, 65.6, 60.2, 45.7, 30.7, 30.0, 29.2, 23.3, 22.8, 18.5; LRESIMS (m/e, resuh of the mixture sample): 993.5 ([M+H]*); HRESIMS (m/e, result of the mixture sample): calcd. for

C65H61N4O6 ([M+H]*) 993.4591, found 993.4590.

5.4.2.13 Photooxygenation of BPD-Ibuprofen (methyl ester) Complex IV-26-E

Following the general photooxygenation procedure (GP-4), BPD-Ibuprofen (methyl ester) Complex IV-26-E (ca. 1.4 mg, 1.4 jumol) and 1,3,5-trimethoxybenzene (ca. 0.5 mg, 3 )Umol) were dissolved in 0.5 mL CÔDÔ with an NMR-determined molar ratio of 0.45 {IV-26-

E/intemal standard). Photoirradiation of the reaction solution for 1.5 min yielded

hydroperoxide IV-44-Z (60%). The GC yield of total releasable ibuprofen methyl ester was

33%.

5.5 Crystal Data and Details of the Structure Determination Empirical Formula C,37HiooN8P4Cl4Zn2Pd2

Formula Weight 2467.47

Crystal Color, Habit Red, needle

Crystal Dimensions 0.50x0.10x0.10 mm

Crystal System Monoclinic

Lattice Type Primitive

Lattice Parameters a = 13.304(1) Â b = 29.414(3) Â c = 14.427(1) Â l3 = 90.818(3)" V = 5644.8(8)

Space group P2, (#4)

Z value 2

Dcalc 1.452 g/cm^

Fooo 2516.00

M(MoKa) 9.42 cm"'

Diffractometer Rigaku/ADSC CCD

Radiation MoKa(X= 0.71069 Â) graphite monochromated

Detector Aperture 94 mm x 94 mm

Data Images 460 exposures @ 55.0 seconds

0 oscillation Range (x = -90.0) 0.0 - 190.0" u oscillation Range (x = -90.0) 17.0-23.0° Detector Position 38.81 mm

Detector Swing Angle -5.53" 55.7" Temperature -100.0+ 0.1OC

No. of Reflections Measured Total: 44251 Unique: 22575 (Rint = 0.087; Friedels not

Corrections Lorentz-polarization Absorption/ scaling.decay (corr. factors: 0.7531 - 1.0000)

Structure Solution Direct Methods (SIR97)

Refinement Full-matrix least-squares

Function Minimized Ew(Fo^ - Fc^f

Least Squares Weights w = 1/(7^ (Fo^) + (0.0847 • P)^ where P = (Max(Fo^O) + 2 • Fc^)/3

Anomalous Dispersion All non-hydrogen atoms

No. Observations (I>0.00a(I)) 22575

No. Variables 1417

Reflection/Parameter Ratio 15.93

Residuals (refined on F^, all data): R; wR2 0.112; 0.221

Goodness of Fit Indicator 1.05

Max Shift/Error in Final Cycle 0.00

No. Observations (I>2a(I)) 15404

Residuals (refined on F, I>3a(I)): R; wR2 0.079; 0.181

Maximum peak in Final Diff. Map 2.84 e/Â^

-1.39 eVi^ Minimum peak in Final Diff. Map Empirical Formula C52H44N6O2

Formula Weight 784.93

Crystal Color, Habit red, plate

Crystal Dimensions 0.25x0.10x0.02 mm

Crystal System Triclinic

Lattice Type Primitive

Lattice Parameters a = 9.8840(8) Â b= 12.5369(9) A c= 18.067(2) Â a =92.419(3)» /3 = 94.911(3)" 7=97.552(4)"

V = 2208.0(3)

Space group P-1 (#2)

Z value 2

Dcalc 1.481 g/cm^

Fooo 828.00

H(MoKa) 0.73 cm"'

Dififractometer Bruker X8 APEX

Radiation MoKa(X = 0.71073 Â) graphite monochromated

Data Images 1125 exposures @ 60.0 seconds Detector Position 37.99 mm 45.0" Temperature -100.0+ 0.1OC No. of Reflections Measured Total: 21224 Unique: 5506 (R^t^ 0.091)

Corrections Lorentz-polarization Absorption (T^in = 0.828, Tmax= 0.999)

Structure Solution Direct Methods (SIR97)

Refinement Full-matrix least-squares on F^

Function Minimized Ew(Fo^ - Fc^

Least Squares Weights w = 1/(0^ (Fo^) + (0.1776 • P)^+O.OOOP)

Anomalous Dispersion All non-hydrogen atoms

No. Observations (I>0.00(7(I)) 5506

No. Variables 468

Reflection/Parameter Ratio 11.76

Residuals (refined on F^, all data): RI; wR2 0.199; 0.331

Goodness of Fit Indicator 1.7

Max Shift/Error in Final Cycle 0.00

No. Observations (I>2.00ff(I)) 2525

Residuals (refined on F): RI; wR2 0.108; 0.292

Maximum peak in Final Diff. Map 1.16 eVi'

Minimum peak in Final Diff. Map -0.47 e/À^ REFERENCES

1. Bonnett, R., In The Porphyrins, Dolphin, D., Ed. Academic Press: New York, 1978;

Vol. l,pp 1.

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