First Total Synthesis of the Novel Brominated Polyacetylenic Diol (+) – Diplyne D and Progress Towards the Total Synthesis of (+) - Diplyne E

A thesis submitted to the Miami University Honors Program in partial fulfillment of the requirements for University Honors with Distinction

Amanda Lea Jones

May, 2005 Oxford, Ohio

ii Abstract

First Total Synthesis of the Novel Brominated Polyacetylenic Diol (+) – Diplyne D and Progress Towards the Total Synthesis of (+) - Diplyne E

by Amanda Lea Jones

This thesis describes the methodology and experimental work towards the total

synthesis of two novel brominated polyacetylenic diols, diplynes D and E (4-5), isolated from the Philippines sponge Diplastrella sp. The work contained herein represents the first reported synthesis of (+) - diplyne D. These two compounds, along with others isolated from Diplastrella (1-3), inhibited HIV-1 integrase. The synthetic route for diplyne D involved a Cadiot-Chodkiewicz coupling reaction to assemble the right hand portion of the molecule and two Sonogashira coupling reactions to create the diyne and vinyl bromide framework. The stereogenic center was derived from D-mannitol. Once diplyne D had been completed, the focus was shifted to diplyne E. The goal was to create diplyne E through a more convergent synthesis, namely the Sonogashira coupling of the

bromine containing enyne to the remaining part of the molecule, which should be easily

prepared due to its similarity to diplyne D. While the right hand portion of the molecule

has been successfully completed, attempts at the preparation of the enyne fragment have

been unsuccessful to date. It is hoped that further research will lead to preparation of the

desired product, in which case diplyne E should rapidly follow.

iii

First Total Synthesis of the Novel Brominated Polyacetylenic Diol (+) – Diplyne D and Progress Towards the Total Synthesis of (+) - Diplyne E

By Amanda Lea Jones

Approved by:

______, Advisor Dr. Benjamin W. Gung

______, Reader Dr. Michael W. Crowder

______, Reader Mr. Craig R. Gibeau

Accepted by:

______, Director University Honors Program

iv Acknowledgments

I would like to thank my advisor, Dr. Benjamin Gung, for his knowledge, guidance, and support throughout the duration of this project as well as my entire

undergraduate research career at Miami University. In addition, I would like to thank

each member of the Gung research group I have come to know over the last two years for

their help and patience. Thanks also to the Arnold and Mabel Beckman Foundation for

financially supporting this project. Last but not least, thanks to all of my family and

friends for always believing in me.

v Table of Contents Page List of Abbreviations vii List of Figures viii List of Schemes ix List of Structures x Chapter 1: Introduction 1 Chapter 2: The Total Synthesis of (+) – Diplyne D 2.1 Introduction 7 2.2 Results and Discussion 8 2.3 Conclusion 10 2.4 Experimental 11 Chapter 3: Progress Towards the Total Synthesis of (+) - Diplyne E 3.1 Introduction 19 3.2 Results and Discussion 21 3.3 Experimental 25 Chapter 4: References 31 Chapter 5: Spectra for Selected Compounds 34

vi List of Abbreviations

DMSO dimethyl sulfoxide

Et ethyl

HRMS high resolution mass spectrometry i-Pr isopropyl

IR infrared

Me methyl

NaHMDS sodium bis(trimethylsilyl)amide

NBS N - bromosuccinimide

NMR nuclear magnetic resonance

ppm parts per million

rt room temperature

sat. saturated

TBAF tetrabutylammonium fluoride

TBDPS tert-butyldiphenylsilyl

TEA triethylamine

THF tetrahydrofuran

TIPS triisopropylsilyl

TMS trimethylsilyl

UV ultraviolet

vii List of Figures

Figure 1 (-) – Minquartynoic acid

Figure 2 Diplynes A-E isolated from Diplastrella sp.

Figure 3 A brominated polyacetylenic acid isolated from

Xestospongia muta

Figure 4 Retrosynthetic analysis of diplyne D 4

Figure 5 Retrosynthetic analysis of (+) – diplyne E 5

Figure 6 Sonogashira coupling reactions of vinyl halides with

silyl acetylenes

viii List of Schemes

Scheme 1 Synthesis of (+) – diplyne D

Scheme 2 Synthesis of advanced intermediate 19

Scheme 3 Synthetic attempts toward enyne 20

ix List of Structures

Br 1 OH OH

Diplyne A

Br OH 2 OH

Diplyne B

Br OH 3 OH

Diplyne C

Br OH 4 OH

Diplyne D

x Br OH 5 OH

Diplyne E

O Br O 6

4-Bromoethynyl-2,2-dimethyl-[1,3]dioxolane

O O 7

4-Deca-1,3,9-triynyl-2,2-dimethyl-[1,3]dioxolane

O O O 8 O

Cadiot Chodkiewicz coupling of 6 to both ends of 1,7-octadiyne

Br O O 9

4-(10-Bromo-deca-1,3,9-triynyl)-dimethyl-[1,3]dioxolane

xi TIPS O O 10

[12-(2,2-Dimethyl-[1,3]dioxolan-4-yl)-dodeca-1,3,9,11-tetraynyl]-triisopropyl-silane

TIPS OH 11 OH

14-Triisopropylsilanyl-tetradeca-3,5,11,13-tetrayne-1,2-diol

OH OH 12

Tetradeca-3,5,11,13-tetrayne-1,2-diol

H Br 13

1-Bromo-but-1-ene-3-yne

14 H

1-Iodo-oct-1-ene-7-yne

HO 15

6-Heptyn-1-ol

xii HO

O O 16

9-(2,2-dimethyl-[1,3]dioxolan-4-yl)-nona-6,8-diyne-1-ol

O O 17

9-(2,2-dimethyl-[1,3]dioxolan-4-yl)-nona-6,8-diynal

O 18 O

4-(10-Iodo-dec-9-ene-1,3-diynyl)-2,2-dimethyl-[1,3]-dioxolane

OH OH 19

12-Iodo-dodec-11-ene-3,5-diyne-1,2-diol

TIPS Br 20

(4-Bromo-but-3-ene-1-ynyl)-trisopropylsilane

xiii TIPS TIPS 21

1,4-Bis-trisopropylsilanyli-buta-1,3-diyne

xiv

Chapter 1

Introduction

1 The total synthesis of natural products is a branch of synthetic organic chemistry that stems from the desire to prepare biologically active molecules that have been isolated from natural sources. The quest for new treatments and cures for debilitating or fatal diseases has promoted the rapid expansion of this field. In addition, it is becoming ever more important to have a means by which natural products can be prepared efficiently and economically, since most natural sources, such as plants or marine sponges, are limited resources and may produce only small amounts of each compound.

One particular group of compounds that has been receiving increased interest over the past few years are polyacetylenes. One example of such is (-) – minquartynoic acid, an anti-cancer, anti-HIV natural product synthesized recently1 (see Figure 1).

Figure 1

CO2H (-) – Minquartynoic acid

Not only do these types of molecules occur often in nature, but many show potent biological activity and provide challenging architectures that attract the interest of organic chemists. The desire to synthesize targets that satisfy these properties was the main basis for this research and led to interest in five novel brominated polyacetylenic diols, diplynes A-E (1-5), shown in Figure 2.

2 Figure 2

Br 1 OH OH

Br OH 2 OH

Br OH 3 OH

Br OH 4 OH

Br OH 5 OH

Diplynes A-E isolated from Diplastrella sp.

Each of these compounds was isolated from the Philippines sponge Diplastrella sp. and showed HIV-1 integrase inhibitory activity in bioassay-guided fractionation.2 The HIV

virus, as is well known, leads to AIDS and is becoming more prevalent in today’s society.

HIV-1 integrase is an enzyme responsible for integrating viral DNA into the DNA of a

healthy cell, thereby causing the healthy cell to now create viral proteins.3 The discovery of effective treatments is biomedically important, and the potential anti-HIV properties of these brominated polyacetylenic diols is therefore a main reason for synthesizing this group of natural products.

3 In addition to the polyacetylenic portions, there are other structural features of the

diplyne compounds worth noting. Each has a characteristic diol end group and one stereogenic center at C2. Due to the small amount of each compound isolated, the absolute configuration of this stereocenter was not determined in the initial report.2

However, (+) - diplyne A was recently synthesized and found to have an (S)

configuration.4 This led to the conclusion that the naturally occurring (-) - diplyne A must

have an (R) configuration at C2.4 Due to the structural similarity between 1-5, the structures of the other naturally occurring diplynes have been tentatively assigned (R) as well.4

Another characteristic of compounds 1-5 is the vinyl bromide group. More and

more brominated compounds are reported each year as coming from marine sources,2 and

many of these compounds exhibit favorable biological activities. For example,

brominated polyacetylenic acids isolated from Xestospongia muta5 (Figure 3) have been shown to inhibit HIV protease.5

Figure 3

COOH Brominated polyacetylenic acid isolated from Xestospongia muta

This compound shown in Figure 3 has striking similarities to the diplyne family of

compounds. However, 1-5 are the first brominated polyacetylenic diols that have been

reported.2

4 This thesis describes the methodology and experimental work concerning the first total synthesis of (+) - diplyne D 4 and synthetic attempts toward a member of the same family of compounds, (+) - diplyne E 5. These two compounds, along with others isolated from Diplastrella (1-3), showed activity in the HIV-1 integrase inhibition assay.

Due to the prevalence of the HIV virus in today’s society, there is high demand for effective treatment, which gives a basis for pursuing these two compounds.

Chapter 2

The Total Synthesis of (+) - Diplyne D

6 2.1 Introduction

Diplyne D 4 is a member of a family of five novel brominated polyacetylenic diols isolated from the marine sponge Diplastrella sp., which showed HIV-1 integrase inhibitory activity when subjected to a bioassay-guided fractionation.2 Based on previous

work done by other members of my research group1, 6-7 involving the synthesis of

polyacetylenes, a retrosynthetic analysis was developed (see Figure 4).

Figure 4

Sonogashiracoupling

Cadiot-Chodkiewicz coupling

Br OH

OH 4

Retrosynthetic analysis of diplyne D 4

The right hand portion of the molecule containing the stereogenic center is

derived from D-mannitol and then linked to the commercially available 1,7-octadiyne

through a Cadiot-Chodkiewicz coupling reaction.8 The left hand bromine containing

enyne fragment was to be accomplished using two subsequent Sonogashira coupling

reactions.9 The first would extend the carbon backbone by one acetylene unit while the

second would add the vinyl bromide portion by means of a commercially available

cis/trans-1,2 dibromoethylene mixture. With this strategy, an effort was made to

synthesize diplyne D 4.

7 2.2 Results and Discussion

The linear synthesis of diplyne D 4 is outlined in Scheme 1 below.

Scheme 1

O O Br + O 43% 7 O 6 O O CuCl, EtNH2 O . MeOH, NH2OH HCl 16% 8 O

NBS, AgNO3 Br TIPS H 7 O acetone O 94% 9 Pd(II), CuI i-Pr2NH

TIPS O 65% HF.pyridine 10 O THF, 0 oC rt + TIPS TIPS 92% 20% 21

TIPS OH TBAF 11 OH THF 97%

Br Br Br OH Br 4 OH CuI, Pd(0), TEA 12 56%

Starting from the commercially available 1,7-octadiyne, a Cadiot-Choidkiewicz coupling was performed using bromoalkyne 6, which is obtained from a known synthesis that begins with the protected form of D-mannitol and provides the stereocenter.7 The desired

cross-coupling product 7 is afforded in 43% yield.8 Also recovered in this reaction was

8 16% of compound 8, which is merely the coupling of 6 to both ends of the starting

material. Terminal acetylene 7 was then subject to bromination using NBS and AgNO3 in

acetone which gave bromoalkyne 9 in 94% yield.11 A Sonogashira coupling reaction with triisopropylsilyl(TIPS) acetylene catalyzed by Pd(II) and CuI led to the TIPS protected diyne 10 in 65% yield.9 Also isolated in this reaction was 20% of the Glaser

homocoupling product of the TIPS acetylene. The next intention was to remove the TIPS

group using HF.pyridine complex, leaving a terminal diyne to which 1,2-dibromoethylene could be coupled. However, no terminal diyne was isolated; instead, 92% of diol 11 with the TIPS group still intact. Thus, instead of removing the TIPS group, the HF.pyridine complex removed the acetonide protecting group. Since this protecting group needed to be removed eventually in order to provide the final product and since subsequent reactions should not affect the two hydroxyl groups, the synthesis was not hindered by this unexpected result. Due to the fact that 10 was unresponsive to desilation by

HF.pyridine, diol 11 was subjected to basic conditions, namely TBAF in THF. The TIPS group was removed in nearly quantitative yield giving terminal diyne 12, which is a solid, most likely due to the diol functionality. It was interesting to discover that terminal diyne

12 was surprisingly stable in contrast to previous reports mentioning the instability of terminal diynes.12, 13 Lastly, another Sonogashira coupling reaction was performed using

a commercially available mixture of cis/trans-1,2-dibromoethylene in the presence of

Pd(0) and CuI9 to give the synthetic diplyne D 4 in 56% yield as a pale yellow solid with

o a melting point of 103-105 C and [α]D = +7.2, thus confirming that the compound made

was (+) - diplyne D.

9 2.3 Conclusion

The synthesis of (+) – diplyne D was achieved in a linear fashion involving 6

steps and beginning with the commercially available 1,7-octadiyne. The overall yield is

13%, and the synthesis described in Scheme 1 represents the first total synthesis of (+) –

diplyne D, which has an absolute configuration of (S) at C2. There was no assignment of

configuration for the naturally occurring diplyne D 4.2 However, recent synthesis of (+) -

diplyne A has led to the establishment of the C2 stereocenter in naturally occurring (-)

diplyne A 1 as (R).4 Due to the structural similarities between 1 and 4, it can be assumed

that the absolute configuration of diplyne D 4 is also (R). Thus, the synthesis described in

Scheme 1 is more accurately a synthesis of the enantiomer of the naturally occurring compound.

10 2.4 Experimental

All reactions were carried out under nitrogen with magnetic stirring unless otherwise noted. Commercially available starting materials were purchased and used without further purification. Column chromatography was performed using silica gel 40-

63 µm. Reactions were monitored by thin layer chromatography and UV light. NMR spectra were recorded on Bruker 200, 300, or 500 MHz spectrometers. Chemical shifts

(δ) are shown in ppm using trimethylsilane (TMS) as the internal reference, and have the following notation: s = singlet, d = doublet, t = triplet, q = quartet, dd = doublet of doublets, dt = doublet of triplets, ddd = doublet of doublets of doublets, m = multiplet. IR spectra were recorded on a Perkin Elmer Spectrum 2000 FTIR. UV spectra were obtained using a Beckman DU 530 UV/visible spectrophotometer. Optical rotations were measured using Rudolph Autopol III. HRMS spectra were received from the Ohio State

University.

11 O O Br + O 7 O 6 O O CuCl, EtNH2 O . MeOH, NH2OH HCl 8 O

4-Deca-1,3,9-triynyl-2,2-dimethyl-[1,3]dioxolane 7

To a round bottom flask equipped with a stirring bar under an atmosphere of nitrogen was added a solution of NH2OH⋅HCl (32.7 mg, 0.47 mmol) in H2O (0.40 ml),

MeOH (9.5 ml), a 70% aqueous solution of EtNH2 (9.5 ml), and CuCl (46.6 mg, 0.47

mmol). Then 1,7-octadiyne (1.0 g, 9.42 mmol) was added in one portion. Next, a

solution of compound 6 (1.92 g, 9.42 mmol) in MeOH (2 ml) was added over the course

of 0.5 h using a syringe pump. The resulting mixture was stirred for an additional 0.5 h at

room temperature. A solution of KCN (1.76 g) and NH4Cl (7.32 g) in H2O (25 ml) was

then added with vigorous stirring. The resulting mixture was extracted three times with

Et2O and the organic layers dried with MgSO4. The solution was filtered and the solvent

removed under reduced pressure. The crude mixture was purified over a silica gel column

to afford a pale yellow oil (0.94g, 43%), and a second fraction (530mg, 16%).

1 Compound 7: [α]D = +34.70 (MeOH, C = 0.21), H NMR (300MHz, CDCl3): δ

1.35 (3H, s), 1.46 (3H, s), 1.63 (4H, m), 1.93 (1H, t, J = 2.5 Hz), 2.19 (2H, m), 2.30 (2H,

m), 3.91 (1H, dd, J = 6.2, 8.0 Hz), 4.12 (1H, dd, J = 6.4, 7.9 Hz), 4.73 (1H, t, J = 6.2 Hz),

13 C NMR (75MHz, CDCl3): δ 18.28, 19.19, 26.31, 26.51, 27.37, 27.74, 65.14, 66.23,

69.08, 70.11, 71.09, 73.41, 81.79, 84.19, 111.00. Compound 8: [α]D = +47.75 (MeOH,

1 C = 0.49), H NMR (200MHz, CDCl3): δ 1.35 (6H, s), 1.46 (6H, s), 1.62 (4H, m), 2.29

12 (4H, m), 3.92 (2H, dd, J = 6.1, 8.1 Hz), 4.13 (2H, dd, J = 6.4, 8.1 Hz), 4.73 (1H, t, J = 6.3

13 Hz), C NMR (50MHz, CDCl3): δ 19.18, 26.34, 27.39, 65.30, 66.24, 70.13, 71.05,

73.51, 81.56, 111.05.

NBS, AgNO3 Br O O acetone 7 O O 9

4-(10-Bromo-deca-1,3,9-triynyl)-dimethyl-[1,3]dioxolane 9

To a suspension of NBS (812 mg, 4.56 mmol) and compound 7 (897 mg, 3.89 mmol) in acetone (39 ml) at room temperature was added AgNO3 (66.1 mg, 0.39 mmol).

The mixture was stirred at room temperature for 1 h and was then diluted with H2O (75 ml). The aqueous layer was extracted three times with Et2O and the combined organic

layers were dried with MgSO4, filtered, and the solvent removed under reduced pressure.

The crude mixture was purified over a silica gel column to afford the desired product as a

yellow oil (1.08 g, 94%).

1 [α]D = +27.60 (MeOH, C = 2.98), H NMR (300MHz, CDCl3): δ 1.35 (3H, s),

1.46(3H, s), 1.61 (4H, m), 2.21 (2H, m), 2.28 (2H, m), 3.92 (1H, dd, J = 6.2, 7.3 Hz),

13 4.13 (1H, dd, J = 6.7, 7.8 Hz), 4.73 (1H, t, J = 6.1 Hz), C NMR (75MHz, CDCl3): δ

19.19, 19.56, 26.31, 26.51, 27.40, 27.59, 38.67, 65.20, 66.23, 70.12, 71.07, 73.46, 79.97,

81.71, 111.02. HRMS: Calcd for C15H17BrO2 + Na, 331.0310, found M + Na: 331.0309.

13 TIPS O Br TIPS H O 10 O O Pd(II), CuI 9 + TIPS TIPS i-Pr2NH 21

[12-(2,2-Dimethyl-[1,3]dioxolan-4-yl)-dodeca-1,3,9,11-tetraynyl]-triisopropyl-silane

To a solution of compound 9 (1.08 g, 3.49 mmol), TIPS acetylene (956 mg, 5.24 mmol), Pd(PPh3)2Cl2 (245 mg, 0.35 mmol), and CuI (67 mg, 0.35 mmol) in THF (21 ml)

at room temperature was added I-Pr2NH (1.0 ml, 7.15 mmol) with stirring. The reaction

was allowed to proceed for 2 h before quenching with saturated NH4Cl solution and

diluting with Et2O. The organic layer was washed one time with saturated NaCl, dried

over MgSO4, and filtered. The solvent was removed under reduced pressure and the

crude mixture purified over a silica gel column to afford the major product as an orange

oil (936 mg, 65%), and a second fraction as a yellow solid (m.p. 64-66 °C, 249 mg,

20%).

1 Compound 10: [α]D = +31.80 (CHCl3, C = 0.19), H NMR (300MHz, CDCl3): δ

1.06 ( 21H, m), 1.35 (3H, s), 1.47 (3H, s), 1.63 (4H, m), 2.29 (4H, m), 3.92 (1H, dd, J =

6.1, 8.1 Hz), 4.13 (1H, dd, J = 6.4, 8.0 Hz), 4.73 (1H, t, 6.2 Hz), 13C NMR (75MHz,

CDCl3): δ 11.68, 18.94, 19.18 (2), 26.31, 26.50, 27.46 (2), 65.27, 66.23, 66.74, 70.11,

71.05, 73.50, 77.60, 78.24, 80.81, 81.58, 111.02. HRMS: Calcd for C26H38O2Si + Na,

1 433.2539, found M + Na: 433.2545. Compound 21: H NMR (500MHz, CDCl3): δ 1.07

13 (42H, m), C NMR (125MHz, CDCl3): δ 11.32, 18.56, 81.59, 90.20.

14 TIPS TIPS O HF.pyridine OH o 10 O THF, 0 C rt 11 OH

14-Triisopropylsilanyl-tetradeca-3,5,11,13-tetrayne-1,2-diol 11

To a solution of compound 10 (936 mg, 2.28 mmol) in THF (23 ml) at 0 °C was added HF⋅pyridine complex (2.51 ml). The resulting solution was warmed to room temperature and stirred for an additional 18 h. Then, the mixture was diluted with Et2O

and washed one time with saturated NaHCO3 solution and one time with saturated NaCl

solution. The organic layer was then dried over MgSO4, filtered, and the solvent removed

under reduced pressure. The crude mixture was purified over a silica gel column giving a

yellow oil (777 mg, 92%).

1 [α]D = +7.30 (MeOH, C = 0.36), UV (MeOH): 217, 240, 253, 268 nm, H NMR

(300MHz, CDCl3): δ 1.05 (21H, m), 1.63 (4H, m), 2.28 (4H, m), 3.65 (1H, dd, J = 6.5,

11.5 Hz), 3.73 (1H, dd, J = 3.6, 11.5 Hz), 4.46 (1H, dd, 3.8, 6.4 Hz), 13C NMR (75 MHz,

CDCl3): δ 11.67, 18.94, 19.16 (2), 27.45, 27.47, 63.98, 65.09, 66.68, 66.74, 71.42, 73.77,

78.24, 80.83, 81.67, 90.28. HRMS: Calcd for C23H34O2Si + Na: 393.2226, found M +

Na: 393.2223.

TIPS OH TBAF OH 11 OH THF OH 12

Tetradeca-3,5,11,13-tetrayne-1,2-diol 12

To a solution of compound 11 (150 mg, 0.38 mmol) in THF (5 ml) was added

TBAF (1 M, 0.58 ml, 0.58 mmol) and the resulting mixture was stirred for 1.5 h at room

15 temperature. Next, ice water (20 ml) followed by HCl (2 ml) was added and the aqueous

layer was extracted two times with Et2O. The combined organic layers were then washed

once with H2O, dried over MgSO4, filtered, and the solvent removed under reduced

pressure. The crude mixture was purified over a silica gel column to afford a pale brown

solid (m.p. 77-79 °C, 79 mg, 97%).

-1 [α]D = +21.04 (CHCl3, C = 0.20), IR υ cm : 3276, 2937, 2871, 2299, 2223, 1454,

1 1279, 1082, H NMR (300MHz, CDCl3): δ 1.64 (4H, m), 1.96 (1H, t, J = 1.1 Hz), 2.29

(4H, m), 3.67 (1H, dd, J = 6.1, 11.4 Hz), 3.74 (1H, dd, J = 4.0, 11.4 Hz), 4.48 (1H, dd, J =

4.0, 6.1 Hz), 13C NMR (50MHz, MeOH): δ 18.06, 18.29, 27.31, 27.40, 63.51, 64.91,

65.08, 65.67, 66.05, 68.03, 69.66, 75.03, 76.99, 80.22. HRMS: Calcd for C14H14O2 + Na,

237.0891, found M + Na: 237.0885.

Br Br Br OH Br Diplyne D 4 OH CuI, Pd(0), TEA 12

(+) - Diplyne D (4)

To a round bottom flask equipped with a stirring bar and under nitrogen was added triethylamine (3 ml), Pd(PPh3)4 (6.8 mg, 0.006 mmol), CuI (2.2 mg, 0.012 mmol),

a mixture of cis and trans dibromoethylene (73 mg, 0.39 mmol), and compound 12 (21 mg). The resulting solution was stirred at room temperature for 6.5 h. The mixture was then diluted with CHCl3 (5mL) and filtered through a pad of Florisil using CHCl3. The solvents were removed under reduced pressure and the crude mixture purified over a

16 silica gel column to afford the product as a pale yellow solid (m.p. 103-105 °C, 16.7 mg,

56%, 5:1/ E:Z by NMR).

-1 [α]D = +7.18 (MeOH, C = 0.10), UV (MeOH): 290, 273, 258, 221 nm, IR υ cm :

1 3055, 2987, 2927, 2341, 1266, 896, 739, H NMR (300MHz, MeOH-d4): δ 1.62 (4H, m),

2.34 (4H, m), 3.53 (1H, dd, J = 6.6, 11.1 Hz), 3.57 (1H, dd, J = 5.1, 11.1 Hz), 4.33 (1H,

dd, J = 5.3, 6.4 Hz), 6.32 (1H, dt, J = 1.0, 14.0 Hz), 7.00 (1H, d, J = 14.6 Hz), 13C NMR

(125 MHz, MeOH-d4): 19.22, 19.57, 28.27, 28.38, 64.51, 65.89, 65.99, 67.06, 70.59,

72.12, 76.07, 77.13, 81.11, 86.24, 117.74, 123.03. HRMS: Calcd for C16H15BrO2 + Na,

341.0153, found M + Na: 341.0178.

Chapter 3

Progress Towards the Total Synthesis of (+) - Diplyne E

18 3.1 Introduction

Diplyne E 5 is a novel brominated polyacetylenic diol that was recently isolated

from the Philippines sponge Diplastrella sp.2 This compound has many similarities to

diplyne D 4 discussed in chapter 2, including anti-HIV properties as well as a structural

resemblance. Due to the structural similarities between the two, it was believed that the

synthesis of (+) - diplyne E 5 could proceed in a manner related to that of 4. However, it

was also hoped that some aspects of the synthesis could be modified to provide the natural product in a more efficient manner.

It was this train of thought that led to the retrosynthetic analysis shown in Figure

Figure 5

H Br 15 I + Br OH 16 H 5 OH + O Br 8 O

Retrosynthetic analysis of (+) - diplyne E 5

This plan represents a more convergent approach towards the synthesis of the target, which is of use because convergent syntheses are in general more efficient than their linear counterparts.

In the synthetic route proposed above, bromoalkyne 6 will be coupled to the terminal alkyne 14 through a Cadiot-Chodkiewicz coupling reaction.8 This should

proceed smoothly since the synthesis of 6 is already known7 and an analogous reaction

19 was successful in the synthesis of (+) – diplyne D 4. It was thought that the bromine containing enyne fragment 13 could be prepared by means of a Pd(0) mediated

Sonogashira coupling reaction9 between the commercially available mixture of cis/trans

1,2-dibromoethylene and a silyl acetylene. Desilation of this intermediate would be expected to yield the terminal acetylene. Intermediate 13 could then be coupled to the vinyl iodide end of 14 to give (+) - diplyne E 5 after removal of the acetonide protecting group to expose the diol.

20 3.2 Results and Discussion

The synthesis of the adduct of bromoalkyne 6 and compound 14 was attempted

first since a similar reaction had already been optimized. The preparation of intermediate

19 is shown in Scheme 2.

Scheme 2

O O Br i) LiAlH4, Et2O 6 O + HO ii) H3O HO CuCl, Et2NH, 74% 15 . MeOH, NH2OH HCl 61%

HO O

O (COCl)2, DMSO O Et N O 3 O 16 74% 17

I CrCl2, CHI3 THF 17 O 18 O

I HF.pyridine, THF o 18 0 C rt OH 31% (two steps) 19 OH

The starting point was the commercially available 6-heptynoic acid, which was reduced with LiAlH4 in 74% yield to alcohol 15. Using Cadiot-Chodkiewicz conditions analogous

to those given in Scheme 2,8 bromoalkyne 6 was successfully coupled to the terminal

alkyne 15 to give diyne 16 in 61% yield and giving only about 5% of a side product

identified by NMR as the homocoupling product of 6. The hydroxyl function was then

21 oxidized under typical Swern oxidation conditions14 to give aldehyde 17 in 74% yield. A

Takai olefination was then performed using iodoform and Cr(II) in THF.15 TLC and

NMR confirmed the formation of vinyl iodide 18. However, this compound was unable

to be separated from excess CHI3 using silica gel flash chromatography. Therefore, the

acetonide protecting group was removed by using HF.pyridine as discussed in chapter 2,

thereby creating diol 19 which is considerably more polar than CHI3. The two species

were then easily separated, providing the intermediate 19 in an overall yield of 11%.

Focus was then shifted to enyne 13, the last piece needed to complete the total synthesis of (+) - diplyne E 5. The intended strategy involved coupling of TIPS acetylene to a mixture of cis/trans 1,2-dibromoethylene by means of a Sonogashira coupling reaction.9 This approach was expected to work based on literature that reported successful couplings of vinyl halides with silyl acetylenes.16-18 A few examples are

shown in Figure 6 below.

22 Figure 6

TMS I TMS H Pd(PPh ) , CuI, I 3 4 I TEA, 95%

i)TMS H

PdCl2, PPh3, CuI piperidine, 85 oC (H C) N Br (H3C)2N H 3 2 ii)TBAF, THF 73% (two steps)

TBDPS Cl H TBDPS

Pd(PPh3)4, CuI Cl Cl n-PrNH2, 91%

Sonogashira coupling reactions of vinyl halides with silyl acetylenes

However, after attempts with both Pd(0)/CuI and Pd(II)/CuI as co-catalysts, little to none of the intended product 20 has been isolated. Rather, a large amount of the Glaser coupling product 21 of the TIPS acetylene was recovered. See Scheme 3 below for a summary of these findings.

Scheme 3

Pd(PPh3)Cl2, CuI Br OR Br Pd(PPh ) , CuI + TIPS H 3 4 TIPS Br 20 Br Br

Br Br Pd(PPh3)Cl2, CuI + TIPS H TIPS TIPS i-Pr2NH 21 55% Br Br

23 Glaser coupling of terminal acetylenes occurs under conditions when Cu(II) is present as a catalyst.16 The desired Sonogashira coupling, on the other hand, occurs under Cu(I) catalytic conditions.9 Therefore, it is thought that the use of the oxidized form of the palladium catalyst along with a 2 : 1 ratio of CuI : Pd(PPh3)2Cl2 led to conditions which promoted the oxidation of Cu(I) to Cu(II). This explains the isolation of a large amount of the Glaser coupling product 21. It is hoped that further research will lead to conditions which favor the Sonogashira coupling reaction and produce key intermediate 20. The total synthesis of (+) – diplyne E 5 should then quickly follow.

24 3.3 Experimental

63 µm. Reactions were monitored by thin layer chromatography and UV light. NMR spectra were recorded on Bruker 200, 300, or 500 MHz spectrometers. Chemical shifts

Optical rotations were measured using Rudolph Autopol III.

25 O i) LiAlH4, Et2O + HO ii) H3O HO 15

6-Heptyn-1-ol 15

To a round bottom flask equipped with a stirring bar and under nitrogen was made

o a suspension of LiAlH4 (602 mg, 15.88 mmol) in anhydrous Et2O (50 ml) at 0 C. Then a solution of 6-heptynoic acid (1.0 g, 7.94 mmol) in dry Et2O (10 ml) was added dropwise

with vigorous stirring. The mixture was allowed to warm to rt and stir for an additional hour. Next, 1 M HCl (26 ml) was added dropwise and the reaction mixture was stirred for

an additional 0.5 h before being diluted with Et2O. The layers were separated and the

aqueous layer extracted three times with Et2O. The organic layers were combined, dried

over MgSO4, then filtered. The solvent was removed under reduced pressure and the

crude purified using a silica gel column to afford the product as a clear oil (658 mg,

74%).

1 H NMR (300MHz, CDCl3): δ 1.52 (6H, m), 1.91 (1H, t, J = 2.7 Hz), 2.15 (2H,

13 dt, J = 2.5, 6.6 Hz), 3.59 (1H, t, J = 6.4 Hz), C NMR (75 MHz, CDCl3): δ 18.74, 25.28,

28.59, 32.54, 63.03, 68.72, 84.83.

26 O Br HO 6 O HO O CuCl, Et2NH, 15 . MeOH, NH2OH HCl O 16

9-(2,2-dimethyl-[1,3]dioxolan-4-yl)-nona-6,8-diyne-1-ol 16

To a round bottom flask equipped with a stirring bar under an atmosphere of nitrogen was added a solution of NH2OH⋅HCl (6.4 mg, 0.09 mmol) in H2O (0.08 ml),

MeOH (2 ml), a 70% aqueous solution of EtNH2 (2 ml), and CuCl (9.1 mg, 0.09 mmol).

Then alkyne 15 (205 mg, 1.83 mmol) was added in one portion. Next, a solution of

compound 6 (412 mg, 2.02 mmol) in MeOH (1 ml) was added over the course of 0.5 h

using a syringe pump. The resulting mixture was stirred for an additional 1 h at rt. A

solution of KCN (0.35 g) and NH4Cl (1.46 g) in H2O (5 ml) was then added with

vigorous stirring. The resulting mixture was extracted three times with Et2O and the

organic layers dried with MgSO4. The solution was filtered and the solvent removed under reduced pressure. The crude mixture was purified over a silica gel column to afford a yellow oil (261 mg, 61%)

1 [α]D = +42.9 (MeOH, C = 1.1), H NMR (300MHz, CDCl3): δ 1.35 (3H, s), 1.46

(3H, s), 1.52 (6H, m), 2.78 (2H, t, J = 6.5 Hz), 3.62 (2H, t, J = 6.2 Hz), 3.91 (1H, dd, J =

6.2, 8.0 Hz), 4.12 (1H, dd, J = 6.4, 8.0 Hz), 4.73 (1H, t, J = 6.2 Hz), 13C NMR (75 MHz,

CDCl3): δ 19.64, 25.40, 26.31, 26.51, 28.26, 32.56, 63.11, 64.96, 66.25, 70.12, 71.16,

73.30, 82.18, 111.00.

27 HO O

O (COCl)2, DMSO O Et3N O O 16 17

9-(2,2-dimethyl-[1,3]dioxolan-4-yl)-nona-6,8-diynal 17

To a 3-necked round bottom flask equipped with a stirring bar and under nitrogen was added (COCl)2 (0.90 ml, 1.79 mmol) in freshly distilled CH2Cl2 (7 ml). This solution

was cooled to -78 oC and DMSO (0.14 ml, 1.96 mmol) was added dropwise over a period

of 5 min. After stirring for 10 min, a solution of 16 (384 mg, 1.63 mmol) in anhydrous

o CH2Cl2 (3 ml) was added dropwise. After an additional 15 min. at -78 C, TEA (1.42 ml,

10.11 mmol) was added dropwise and the reaction mixture was warmed to -10 oC. Then,

1 M HCl (5 ml) was added and the aqueous layer extracted twice with Et2O. The organic

layers were combined and washed once with H2O before being dried over MgSO4 and filtered. The solvent was removed under reduced pressure and the crude mixture purified over a silica gel column to afford an orange oil (283 mg, 74%).

1 [α]D = +33.7 (MeOH, C = 0.5), H NMR (300MHz, CDCl3): δ 1.35 (3H, s), 1.46

(3H, s), 1.56 (2H, m), 1.70 (2H, m), 2.27 (2H, t, J = 6.8 Hz), 2.44 (1H, dt, J = 1.6, 7.1

Hz), 3.91 (1H, dd, J = 6.1, 8.1 Hz), 4.12 (1H, dd, J = 6.4, 8.1 Hz), 4.73 (1H, t, J = 6.2

13 Hz), 9.72 (1H, d, J = 1.5 Hz), C NMR (75 MHz, CDCl3): δ 19.49, 21.55, 26.29, 26.51,

27.82, 43.62, 65.34, 66.22, 70.10, 71.01, 73.55, 81.47, 111.02, 202.31.

28 O I i)CrCl2, CHI3 THF O ii) HF.pyridine, THF OH o O 0 C rt OH 17 19

12-Iodo-dodec-11-ene-3,5-diyne-1,2-diol 19

To a round bottom flask equipped with a stirring bar under an atmosphere of nitrogen was made a suspension of CrCl2 (1.58 g, 12.84 mmol) in anhydrous THF (6 ml)

o at 0 C. Next, a solution of aldehyde 17 (500 mg, 2.14 mmol) and CHI3 (1.68 g, 4.27

mmol) in anhydrous THF (10 ml) was added dropwise. The reaction mixture was stirred

o at 0 C for 3 h before being diluted with H2O. The layers were separated and the aqueous

layer extracted four times with Et2O. The combined organic layers were dried with

Na2SO4, then filtered. The solvent was removed under reduced pressure and the crude

mixture purified over a silica gel column to remove any metal.

The crude mixture containing vinyl iodide 18 and CHI3 was dissolved in

anhydrous THF (16 ml), then cooled to 0 oC while stirring under an atmosphere of

nitrogen. To the reaction mixture was added HF.pyridine complex (1.6 ml) at 0 oC. The mixture was warmed to rt and allowed to stir 17 h before being diluted with Et2O. The

mixture was washed once each with NaHCO3 and brine. The organic layer was dried over

MgSO4, then filtered. The solvent was removed under reduced pressure and the crude

mixture purified over a silica gel column to afford a pale yellow solid (m.p. 56-57 oC,

162 mg, 32% for two steps).

1 [α]D = +8.9 (MeOH, C = 0.6), H NMR (300MHz, CDCl3): δ 1.50 (4H, m), 2.05

(2H, m), 2.27 (2H, t, J = 6.5 Hz), 2.59 (1H, s), 2.92 (1H, s), 3.65 (1H, dd, J = 6.5, 11.5

Hz), 3.73 (1H, dd, J = 3.4, 11.6 Hz), 4.46 (1H, t, J = 3.9 Hz), 5.99 (1H, dt, J = 1.4, 14.4

29 Hz), 6.46 (1H, dt, J = 7.1, 14.4 Hz), 13C NMR (75 MHz, CDCl3): δ 19.44, 27.64, 27.80,

35.82, 64.01, 64.95, 66.70, 71.51, 73.66, 75.44, 81.99, 146.27.

Chapter 4

References

31 (1) Gung, B. W.; Dickson, H. Org. Let.t, 2002, 4(15), 2517-2519.

(2) Lerch, M. L.; Harper, M. K.; Faulkner, D. J. J. Nat. Prod., 2003, 66, 667-670.

(3) http://adrik.bchs.uh.edu/integrase.html. Mar 4 1998. Accessed Apr 3 2005.

(4) Gung, B. W.; Gibeau, C.; Jones, A. Tetrahedron: Asymmetry, 2004, 15, 3973-

3977.

(5) Patil, A. K.; Kokke, W. C.; Cochran, S.; Francis, T. A.; Tomszek, T.; Westley,

J. W. J. Nat. Prod., 1992, 55(9), 1170-1177.

(6) Gung, B. W.; Kumi, G. J. Org. Chem., 2004, 69, 3488-3492.

(7) Gung, B. W.; Kumi, G. J. Org. Chem., 2003, 68, 5956-5960.

(8) Brandsma, L. Preparative Acetylenic Chemistry, 2nd ed.; Elsevier: New York,

1998; Vol. 34.

(9) Sonogashira, K.; Tohda, T.; Hagihara, N. Tetrahedron Lett., 1975, 4467-4470.

(10) Schmid, C. R.; Bryant, J. D.; Dowlatzedah, M.; Phillips, J. L.; Prather, D. E.;

Schantz, R. D.; Sear, N. L.; Vianco, C. S. J. Org. Chem., 1991, 56, 4056-

4058.

(11) Hofmeister, H.; Annen, K.; Laurent, H.; Wiechart, R. Angew. Chem. Intl. Ed.

English, 1984, 23, 727-729.

(12) Haley, M. M.; Bell, M. L.; Englsh, J. J.; Johnson, C. A.; Weakley, T. J. R. J.

Am. Chem. Soc., 1997, 119, 2956-2957.

(13) Heuft, M. A.; Collins, S. K; Yap, G. P. A.; Fallis, A. G. Org. Lett., 2001, 3,

2883-2886.

32 (14) Marshall, J. A.; Bartley, G. S.; Wallace, E. M. J. Org. Chem., 1996, 61, 5729-

5735.

(15) Takai, K.; Nitta, K.; Utimoto, K. J. Am. Chem. Soc., 1986, 108, 7408-7410.

(16) Tsuji, T.; Ohkita, M.; Ando, K. Suzuki, T. J. Org, Chem., 2000, 65, 4385-

4390.

(17) Nicoud, J. F.; Wong, M. S. Tetrahedron Lett., 1994, 35(33), 6113-6166.

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Chapter 5

Spectra for Selected Compounds

O O 7

4-Deca-1,3,9-triynyl-2,2-dimethyl-[1,3]dioxolane

Spectrum Page

1H NMR 36

13C NMR 37

Br O O 9

4-(10-Bromo-deca-1,3,9-triynyl)-dimethyl-[1,3]dioxolane

Spectrum Page

1H NMR 39

13C NMR 40

TIPS O O 10

[12-(2,2-Dimethyl-[1,3]dioxolan-4-yl)-dodeca-1,3,9,11-tetraynyl]-triisopropyl-silane

Spectrum Page

1H NMR 42

13C NMR 43

TIPS OH 11 OH

14-Triisopropylsilanyl-tetradeca-3,5,11,13-tetrayne-1,2-diol

Spectrum Page

1H NMR 45

13C NMR 46

OH OH 12

Tetradeca-3,5,11,13-tetrayne-1,2-diol

Spectrum Page

1H NMR 48

13C NMR 49

IR 50

Br OH 4 OH

(+) - Diplyne D

Spectrum Page

1H NMR 52

13C NMR 53

IR 54

UV 55

HO 15

6-Heptyn-1-ol

Spectrum Page

1H NMR 57

13C NMR 58

O O 16

9-(2,2-dimethyl-[1,3]dioxolan-4-yl)-nona-6,8-diyne-1-ol

Spectrum Page

1H NMR 60

13C NMR 61

O O 17

9-(2,2-dimethyl-[1,3]dioxolan-4-yl)-nona-6,8-diynal

Spectrum Page

1H NMR 63

13C NMR 64

OH OH 19

12-Iodo-dodec-11-ene-3,5-diyne-1,2-diol

Spectrum Page

1H NMR 66

13C NMR 67