Synthesis of Novel Tröger's Base-Derived Helical Scaffolds

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Master of Chemical Sciences Capstone Projects Department of Chemistry

5-2017

Synthesis of Novel Tröger’s Base-Derived Helical Scaffolds

Rahul Goel University of Pennsylvania, [email protected]

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Goel, Rahul, "Synthesis of Novel Tröger’s Base-Derived Helical Scaffolds" (2017). Master of Chemical Sciences Capstone Projects. 5. https://repository.upenn.edu/mcs_capstones/5

This paper is posted at ScholarlyCommons. https://repository.upenn.edu/mcs_capstones/5 For more information, please contact [email protected]. Synthesis of Novel Tröger’s Base-Derived Helical Scaffolds

Abstract Tröger’s base (TB) is a chiral V-shaped molecule in which the aromatic rings are nearly perpendicular. The overarching goal of this project is to utilize the unique chirality and inherent shape of the Tröger’s base monomer to design, synthesize and study dimeric, tetrameric and octameric TB oligomers, which will form helical structures. We describe here the methodology for the synthesis of novel Tröger’s base diester monomer 13, which is highly soluble in most organic solvents compared to TB systems with methylene bridges. Chiral HPLC resolution of TB monomer 18, using a semiprep chiral AD-H column, gave access to pure enantiomers of the TB monomer. The (-)-enantiomer of 18 was used to synthesize the novel syn diester TB dimer 20, via double Buchwald-Hartwig coupling based phenazine formation. Energy minimization modeling of the syn dimer 20 using Web MO shows a potential binding cleft, which can ultimately be applied for the synthesis of desired tetrameric and octameric scaffolds. The chiral HPLC resolution of TB monomer 18 is expensive, time-consuming and has low scalability. This problem was solved by the synthesis of a menthone-based chiral auxiliary 27, which allows easy access to the enantiopure monomers of TB. The chirality of 27 was utilized to form the diastereomers of menthone TB 33, which were readily separable by column chromatography. These diastereomers were then hydrolyzed to give pure enantiomers of diol TB monomer 34.

Keywords Tröger’s Base, TB, oligomers, Helical, Helical scaffolds, dimer, monomer, tetramer, octamer, menthone, chiral, auxiliary, Chiral resolution of Tröger’s Base

Disciplines Chemistry

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This capstone report is available at ScholarlyCommons: https://repository.upenn.edu/mcs_capstones/5

AN ABSTRACT OF THE CAPSTONE REPORT OF

Rahul Goel for the degree of Master of Chemical Sciences

Title: Synthesis of Novel Tröger’s Base-Derived Helical Scaffolds

Project conducted at: Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104, United States of America Supervisor: Jeffrey D. Winkler Dates of Project: May 6, 2016 to May 1, 2017

Abstract approved:

Professor Jeffrey D. Winkler

Tröger’s base (TB) is a chiral V-shaped molecule in which the aromatic rings are nearly perpendicular. The overarching goal of this project is to utilize the unique chirality and inherent shape of the Tröger’s base monomer to design, synthesize and study dimeric, tetrameric and octameric TB oligomers, which will form helical structures. We describe here the methodology for the synthesis of novel Tröger’s base diester monomer 13, which is highly soluble in most organic solvents compared to TB systems with methylene bridges. Chiral HPLC resolution of TB monomer 18, using a semiprep chiral AD-H column, gave access to pure enantiomers of the TB monomer. The (-)-enantiomer of 18 was used to synthesize the novel syn diester TB dimer 20, via double Buchwald-Hartwig coupling based phenazine formation. Energy minimization modeling of the syn dimer 20 using Web MO shows a potential binding cleft, which can ultimately be applied for the synthesis of desired tetrameric and octameric scaffolds. The chiral HPLC resolution of TB monomer 18 is expensive, time-consuming and has low scalability. This problem was solved by the synthesis of a menthone-based chiral auxiliary 27, which allows easy access to the enantiopure monomers of TB. The chirality of 27 was utilized to form the diastereomers of menthone TB 33, which were readily separable by column chromatography. These diastereomers were then hydrolyzed to give pure enantiomers of diol TB monomer 34.

Synthesis of Novel Tröger’s Base-Derived Helical Scaffolds by Rahul Goel

A CAPSTONE REPORT

submitted to the

University of Pennsylvania

in partial fulfillment of the requirements for the degree of

Master of Chemical Sciences

Presented (May 1, 2017) Commencement (May 2017)

Dedicated to my parents, Rajeev and Kavita Goel

iv ACKNOWLEDGEMENTS

I would first like to thank Professor Jeffrey D. Winkler for all the support and guidance that he has provided me over the last two years. His expert advice and encouragement has not only helped me evolve as a better chemist, but also as a better person. I will be forever grateful to Professor Winkler for giving me the opportunity to be a part of his research group, and learn the necessary skills that will help me during my entire career.

I would also like to thank Dr. Ana-Rita Mayol for her continued support during my time at the University of Pennsylvania. From writing my capstone proposal to writing my final capstone report, Dr. Mayol has helped me during each step of the Master’s program. I would also like to thank Professor Donna Huryn for her valuable guidance, comments and feedback during the last two years.

Next, I would like to thank the members of the Winkler group- Dr. Rosa Cookson. Dr. Michelle Estrada, Dr. Buddha Khatri, Dr. Sara Goldstein, Mike Nicastri, Katie Crocker and Tyler Higgins for being great mentors and friends. Without their patience and instruction, I would not have been able to come this far. I would also like to thank all my MCS friends, who made graduate school a memorable experience.

Last but not the least, I would like to thank my parents, Rajeev and Kavita Goel, for their guidance, support, love and wisdom over the last 25 years. They have always been the constant source of my inspiration during everything that I have ever been a part of. None of this would have been possible without them being there to encourage and motivate me at every step of my journey. I would also like to thank my brother Sahil for always cheering me up during stressful times and being a constant pillar of support throughout.

v TABLE OF CONTENTS

Abstract…………………………...………………………………………………...... i

Title page…………………………………………………………………...……………ii

Approval page………………...………………………………………………………...iii

Dedication……………………....…………………………………………………….…iv

Acknowledgements……………....……………………..…………....………………..v

Table of contents…………………...…………………………………………………..vi

List of figures……………………...... …………………………………………………vii

List of schemes……………...………………………………………………………...viii

List of tables……………………...……………………………………………………..ix

List of appendices……………………...…………………………………………….…x

Introduction………………………………...…………………………………………....1

Materials and methods………………………...……………………………………....7

Results and Discussion……………………………...……………………………….17

Synthesis of TB helical scaffolds……………...…………………………..…17

Preliminary binding studies with Hydroquinone…………………………….23

Menthone-based chiral auxiliary for better separation of enantiomers……………………………………………………………….……25

Conclusion…………………………...………………………………………………...29

References……………...………………...…………………………………………...30

Appendices………………..……………..……...……………………………………..32

LIST OF FIGURES

Figure 1. Tröger’s base………………………………………………………….….....1

Figure 2. Existing helical systems by Hamilton, Boger and Arora………………...2

Figure 3. TB monomer 1, extended pseudo-dimers syn 2 and 3, and anti 4…………..…………………………………………………………...…3

Figure 4. The ABA problem associated with conventional TB synthesis…………3

Figure 5. Double Buchwald- Hartwig coupling based synthesis of phenazine 5………………………..………………………………………...4

Figure 6. Energy minimized space-filling models (MM2) of the TB monomer 1...... 4

Figure 7. Energy minimized space-filling models of A) 6’, syn diastereomer of the TB dimer 6; C) 7’, anti diastereomer of the TB dimer 7……..………...……………………………………………...4

Figure 8. Energy minimized space filling models of A) 8’, side view of TB Tetramer 8; B) 8’’, top view of 8; C) 9’, side view of TB octamer 9; D) 9’’, top view of 9…....……………….……………………...5

Figure 9. TB monomer 10 and the syn TB phenazine dimer 6…………………....6

Figure 10. Energy minimized Web MO model of the TB dimer 14……..………..18

Figure 11. Energy minimized Web MO models of A) 15’, top view of diester TB tetramer 15; B) 15’’, side view of 15…………………...... 19

Figure 12. Energy minimized Web MO models of A) 16’, top view of diester TB octamer 16 and B) 16’’, side view of 16…………….….….20

Figure 13. 1H NMR peak shifts for syn dimer (graph 1,2,3 and 4) and hydroquinone (graph 5), with the increasing concentration of hydroquinone in 2:1 THF-d8/D2O………………………………………..24

vii LIST OF SCHEMES

Scheme 1. Proposed synthesis showing the formation of more soluble monomer, which will be used to synthesize the syn TB oligomers……………...... …7

Scheme 2. Synthesis of methylene TB 11, diazocine 12 and Diester TB monomer 13..……………...…………………………………………18

Scheme 3. Synthesis of Diester TB monomer 17 and 18, and chiral resolution of diester TB monomer 18……...…………………………..21

Scheme 4. Synthesis of bromoaniline Diester TB 19 and bis-Boc diester TB dimer 20………...……………………………………………22

Scheme 5. Synthesis of mono-Boc TB dimer 21, bromoaniline TB dimer 22 and proposed tetramer 23……………………………...……23

Scheme 6. Proposed synthesis of menthone-based chiral auxiliary 27………………………………………………………………..25

Scheme 7. Ketalization of menthone 24, to form trans menthone ketal 25, and undesired cis menthone ketal 28………...…………….26

Scheme 8. Synthesis of menthone-based chiral auxiliary 27…………………….27

Scheme 9. Synthesis of menthone TB monomer 27 and diol TB monomer 34………………………………...………………………..28

viii LIST OF TABLES

Table 1. Stability study of diester TB 13 compared to methylene TB 11…..……18

Table 2. Lewis Acid Screen for diastereoselectivity in the formation of menthone TB 33………………………...……………………………….28

ix LIST OF APPENDICES

1H NMR spectrum of diazocine 12..………………………………………………….32

13C NMR spectrum of diazocine 12...... 33

1H NMR spectrum of dibromo diester TB monomer 13…..………………………..34

13C NMR spectrum of dibromo diester TB monomer 13……..…………………….35

1H NMR spectrum of bis-Boc diester TB monomer 17………………...…………..36

13C NMR spectrum of bis-Boc diester TB monomer 17……………………………37

1H NMR spectrum of mono-Boc diester TB monomer 18……………...………….38

13C NMR spectrum of mono-Boc diester TB monomer 18...... 39

1H NMR spectrum of bromoaniline diester TB monomer 19………………………40

13C NMR spectrum of bromoaniline diester TB monomer 19...... 41

1H NMR spectrum of bis-Boc diester TB dimer 20...... 42

13C NMR spectrum of bis-Boc diester TB dimer 20………………………………...43

1H NMR spectrum of mono-Boc diester TB dimer 21………...……………………44

13C NMR spectrum of mono-Boc diester TB dimer 21……………………………..45

1H NMR spectrum of bromoaniline diester TB dimer 22…………………………..46

13C NMR spectrum of bromoaniline diester TB dimer 22……...…………………..47

1H NMR spectrum of bis(trimethylsilyloxy) ether propanone 30…………………..48

13C NMR spectrum of bis(trimethylsilyloxy) ether propanone 30…………………49

1H NMR spectrum of bis(trimethylsilyloxy) vinyl ether 31………………………….50

13C NMR spectrum of bis(trimethylsilyloxy) vinyl ether 31…………………………51

1H NMR spectrum of methylene spiroketal 32……………………………………...52

13C NMR spectrum of methylene spiroketal 32...... 53

1H NMR spectrum of spiroketone 27………………………………………………...54

13C NMR spectrum of spiroketone 27………………………………………………..55

1H NMR spectrum of (+)-menthone TB monomer 33………………………………56

13C NMR spectrum of (+)- menthone TB monomer 33…………………………….57

1H NMR spectrum of (-)-menthone TB monomer 33……………………………….58

13C NMR spectrum of (-)-menthone TB monomer 33…………………………...…59

1H NMR spectrum of diol TB monomer 34………………………………………….60

13C NMR spectrum of diol TB monomer 34…………………………………………61

Fully assigned 1H NMR spectrum of bis-Boc diester TB dimer 20...... 62

Fully assigned 13C NMR spectrum of bis-Boc diester TB dimer 20………….…...63

HPLC chromatographs- Chiral AD-H resolution of mono-Boc TB 18……...... …64

DynaFit Script- Preliminary binding studies between bis-Boc dimer 20 and hydroquinone…………...... ………………………………...... …66

INTRODUCTION

Helical structures represent an important structural motif in nature, and have been of great interest to chemists. The overarching goal of this project is directed towards the design, synthesis and exploring applications of novel Tröger’s base- derived helical systems. Tröger’s base (TB) was first synthesized by Carl Julius Ludwig Tröger in 1887 as an unexpected product of mixing p-toluidine and dimethoxymethane in aqueous HCl. However, the correct chemical structure was determined in 1935 by Spielman as 2,8-dimethyl-6H,12H-5,11-methano dibenzo[b,f][1,5]diazocine, almost 50 years after the discovery of the molecule (Figure 1).1

N H3C

N CH3

Figure 1. Tröger’s base

Tröger’s base consists of two aromatic rings fused to a bicyclic aliphatic unit, where the aromatic rings are nearly perpendicular, giving TB its rigid V-shape. TB is a chiral C2-symmetric molecule and does not contain any traditional carbon stereocenters. The unusual inherent chirality in the system is derived from the shape of the molecule. The methylene bridge in TB inhibits pyramidal inversion of the two bridgehead nitrogen atoms, making them configurationally stable stereocenters. TB is one of the first compounds to be isolated, where nitrogen stereogenic centers were observed.

We hope to utilize the unique chirality and inherent shape of Tröger’s base to make helical structures, by synthesizing oligomers of TB. The objective of this capstone project is to synthesize novel Tröger’s base-derived helical systems. These novel TB helical scaffolds offer significant advantages over existing synthetic helical structures. The helical systems developed by Hamilton2, Boger3, Arora4, and others feature biaryl or pseudo-peptidic backbones, each of which is conformationally flexible (Figure 2). Most of these helical systems are achiral. On the other hand, our novel TB helical scaffolds utilize a readily available chiral building block whose three dimensional structure is precisely defined. This property makes the TB systems more rigid and removes the conformational flexibility of previously described systems.1

O RHN Ph HO

O NH O

O NH

O NH OH HOOC O

Boger Hamilton

R O BocN O R N O N O R N R

Arora

Figure 2. Existing helical systems by Hamilton, Boger and Arora.2,3,4

The unique structural features of TB scaffolds can have several possible applications. Firstly, the rigidity and well-defined structure of TB can be of great use for molecular recognition, compared to other systems where only one or a few of the many possible conformations could be used. Extensive literature precedent for the functionalization of the TB monomer shows that we can potentially introduce suitable functional groups on structurally well-defined TB scaffolds for recognition of and binding to desired targets and surfaces.5 It can also help in the introduction of functionalities that can be used to optimize biophysical properties like solubility. Secondly, the potential molecular recognition utility of these novel spatially addressable scaffolds can possibly be utilized to disrupt protein-protein interactions, a ubiquitous signaling motif in biological systems.6 We hope that these novel TB helices, with defined chirality and dimensionality, can exploit specific recognition interactions and act as novel peptide mimics to inhibit protein-protein interactions (PPIs). Lastly, the chirality of these unique helical scaffolds can prove useful in organometallic chemistry for the design of chiral catalysts. The synthesis of these spatially addressable helical systems will solve a long-standing problem in chemistry, by providing an efficient method for the controlled synthesis of chemical structures with functional groups at well-defined distances in three-dimensional space.

We devised a strategy for experimental design by evaluating the current problems associated with the synthesis of TB systems. TB 1 can be readily synthesized from aniline and formaldehyde in acidic medium.7 However, the extension of this strategy to selectively synthesize extended pseudo-dimer

systems such as 2 is difficult (Figure 3). It has been established by the work done by Kral and coworkers that the reaction of 1,4-diaminobenzene with formaldehyde and aniline leads to formation of a mixture of syn products 2 and 3 and the anti product 4 in low yields (10-15%).8

N N N

N N N 1 2

N N N N

N N N N 4 3 Figure 3. TB monomer 1 and extended pseudo-dimers syn 2, syn 3, and anti 4.8

Another problem associated with this method of synthesis is the uncontrollability of the reaction, also called the ABA problem (Figure 4). Reaction of aniline A and 1,4-diaminobenzene B with paraformaldehyde in acidic medium gives the desired product AB and the undesired products AA and BB. Further reaction of AB with A leads to the formation the desired product ABA. However, AB also reacts with B to give the undesired product ABB, which can further undergo a reaction with A or B to form pseudo-trimers. Hence, this reaction strategy is neither stereoselective nor chemoselective, and produces several undesired side products.

NH2 N N N NH2 NH2 + + (CH2O)n N H2N N A N TFA AA AB BB +

NH2

NH NH2 H2N 2 B H2N A B

(CH2O)n, TFA (CH2O)n, TFA

N N N N NH2

N N N N ABA ABB Figure 4. The ABA problem associated with conventional TB synthesis.8

Consequently, one of the biggest synthetic challenges is seeking effective strategies to connect two aromatic rings. The phenazine synthesis developed by

the Winkler group (Figure 5) can provide a solution, where the double Buchwald- Hartwig coupling of 2-bromoaniline with itself leads to the formation of phenazine 5.9

Pd(OAc) , 2 N NH2 ligand, solvent Br N 5 Figure 5. Double Buchwald-Hartwig coupling based synthesis of phenazine 5.9

We hypothesize that connecting TB aromatic rings by this novel phenazine synthesis can prove valuable in synthesizing TB oligomers. In order to test our hypothesis and visualize how Tröger’s base monomer (Figure 6) and its phenazine-based oligomers (dimer, tetramer and octamer) assemble in three- dimensional space in their lowest energy conformation, energy minimization on the structures was performed using Web MO.

Figure 6. Energy minimized space-filling models of the TB monomer 1.

A) B)

6’ 7’

N N N N N N

6 7

Figure 7. Energy minimized space-filling models of A) 6’, syn diastereomer of the TB dimer 6; C) 7’, anti diastereomer of the TB dimer 7.

A) B)

8’ 8’’

N N N N N

N N N N N 2 8

C) D)

9’ 9’’

N N N N N

N N N N N 6 9 Figure 8. Energy minimized space filling models of A) 8’, side view of TB Tetramer 8; B) 8’’, top view of 8; C) 9’, side view of TB octamer 9; D) 9’’, top view of 9.

As mentioned above, the dimer can exist as either the syn or the anti diastereomer (Figure 7). In the syn configuration, the methylene bridges on TB monomers are in the same direction- either both are facing up or both are facing down. However, the methylene bridges are in opposite directions in case of the anti diastereomer. It is interesting that the syn diastereomer 6 of the Tröger’s base dimer has a well-defined potential binding cleft, which is missing in the anti diastereomer 7. We are particularly interested in the syn configuration, since oligomerization of the syn diastereomer can form the desired helical structures. Further energy minimized Web MO modeling (Gaussian- PM3) of the tetrameric TB compound 8 and the octameric TB compound 9 using the syn configuration for all methylene bridges in the system revealed the desired helicity of the tetrameric and octameric structures (Figure 8).

Unpublished work done in the Winkler group has shown that connecting two TB subunits 10 of the same chirality via phenazine formation leads to the formation of only the syn product 6 of the same chirality (Figure 9). We will use this novel double Buchwald-Hartwig phenazine synthesis for the formation of the syn oligomers of TB.9

Br N N N NH2 N

N N N N 10 6 Figure 9. TB monomer 10 and the syn TB phenazine dimer 6

However, previous attempts in the Winkler group to synthesize the dimer 6 and the tetramer 8 have proved to be more difficult than originally anticipated due to solubility issues, resulting in low yields. TB monomer 11 has very low solubility in most of the organic solvents, except CH2Cl2 and DMSO. In order to address the issue of insolubility, we plan to replace the hydrogens on the methylene bridge of TB 11 with esters, based on the work on C-shaped strips for molecular recognition done by Schneebeli.10 We envision that replacing hydrogens with esters would not only increase the solubility of the system, but these esters can act as functional handles for the introduction of both hydrophobic and hydrophilic groups and can give access to several other functional groups like acid, amides, alcohols, ketones (by forming Weinreb amides) and can also undergo trans- esterification if there is a need to increase or decrease the length of ester alkyl chain during late stage synthesis. For the purposes of our synthesis, we will use ethyl esters. A generic scheme for the proposed synthesis is shown below (Scheme 1), where we will synthesize a more soluble TB monomer using 4- bromoaniline, followed by the synthesis of syn TB oligomers.

Scheme 1. Proposed synthesis showing the formation of a more soluble monomer, which will be used to synthesize the syn TB oligomers

R R1 1

N R NH2 2

+ (CH2O)n Br R2 N More soluble monomer

R R1 1

N R3 R R1 1 N N N N R R1 1 N N N N

R3 N n=0, 2, 4

syn TB Oligomers

MATERIALS AND METHODS

General. Solvents used for extraction and purification were HPLC grade from Fisher. Unless otherwise indicated, all reactions were run under an inert atmosphere of argon. Anhydrous tetrahydrofuran, ethyl ether, dichloromethane, and toluene were obtained via passage through an activated alumina column. Merck pre-coated silica gel plates (250 mm, 60 F254) were used for analytical TLC. Spots were visualized using 254 nm ultraviolet light, with either phosphomolybdic acid (PMA) or potassium permanganate stains as visualizing agents. Chromatographic purifications were performed on Sorbent Technologies silica gel (particle size 32-63 microns). 1H and 13C NMR spectra were recorded at 500 MHz and 126 MHz in CDCl3, C6D6, or CD3OD on a Bruker AVII-500 or DRX-500 spectrometer. Chemical shifts are reported relative to internal 1 13 1 13 chloroform (δ 7.26 for H, δ 77.16 for C), C6D6 (δ 7.16 for H, δ 128.06 for C), 1 13 or CD3OD (δ 3.31 for H, δ 49.0 for C). Infrared spectra were recorded on a NaCl plate using a Perkin-Elmer 1600 series Fourier transform spectrometer. High-resolution mass spectra were obtained by Dr. Chuck Ross, at the University of Pennsylvania Mass Spectrometry Center on an Autospec high-resolution double-focusing electrospray ionization/chemical ionization spectrometer with either DEC 11/73 or OPUS software data system. Specific

rotation (αd) for chiral compounds was measured using a Jasco P-2000 digital polarimeter. Melting points were obtained on a Thomas Hoover capillary melting point apparatus and are uncorrected.

N Br

Br N (±)-2,8-dibromo-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine 11: To a round bottom flask with a stir bar was added TFA (475 mL), which was then cooled to -15°C, followed by the addition of a solid mixture of 4-bromoaniline (40.8 g, 240 mmol) and paraformaldehyde (14.25 g, 480 mmol) portion wise over the course of an hour via a solid addition funnel. The reaction mixture was then allowed to warm to 23°C and stirred for 3 days. The TFA was quenched by carefully adding saturated ammonium hydroxide at 0°C until the pH turned basic (~12), followed by an extraction of aqueous layer using dichloromethane (4 x 250 mL). The combined organic layers were washed with brine, dried over MgSO4 and concentrated in vacuo. The crude product was dissolved in 200 mL of 1:4 ethyl acetate/hexanes and stirred vigorously at room temperature for 12 hours. The precipitate was collected via vacuum filtration using a Büchner funnel, and washed with an additional 150 mL of cold 1:4 ethyl acetate/hexanes to give the product (35 g, 92.08 mmol, 78%) as a light yellow solid. M.P.164-166°C; 1H NMR (500 MHz, Chloroform-d): 7.27 (dd, 2 H, J = 8.6 Hz, J = 2.1 Hz) 7.04 (d, 2 H, J = 2.1 Hz), 6.99 (d, 2 H, J = 8.6 Hz), 4.63 (d, 2 H, J = 16.8 Hz), 4.24 (s, 2 H) d = 13 4.09 (d, 2 H, J = 16.8 Hz); C NMR (126 MHz, CDCl3): 147.1, 130.8, 129.9, + + 127.1, 117.0, 67.1, 58.6; HRMS: (ES ) calculated for C15H13Br2N2 [M+H] : 378.9445, found: 378.9435. Characterization data matches the literature values.7

HN Br

Br N H 2,8-dibromo-5,6,11,12-tetrahydrodibenzo[b,f][1,5]diazocine 12: Trifluoro- acetic anhydride (54 mL) was added via dropping funnel to a solution of 2,8- dibromo-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine 11 (16 g, 42.3 mmol) in CH2Cl2 (110 mL) at 0°C. The solution was warmed to 23°C and stirred for 1 h when it was cooled back down to 0°C. The reaction was quenched slowly with water (100 mL) and then neutralized to pH 7 with saturated aqueous NaHCO3. The aqueous phase was extracted with CH2Cl2 (4 x 200 mL) and the combined organic layers were washed with brine (300 mL), dried over MgSO4 and concentrated in vacuo. The residue was dissolved in a solution of sodium hydroxide (8.5 g, 212 mmol) in EtOH (430 mL), and the mixture was stirred for 16 h at 23°C. The reaction was concentrated in vacuo, and CH2Cl2 (300 mL) and water (500 mL) were added. The aqueous phase was extracted with CH2Cl2 (3 x 200 mL). The combined organic layers were dried over MgSO4 and concentrated in vacuo. Purification by column chromatography (20:80 hexanes/CH2Cl2 to 100% CH2Cl2) gave product 12 (7.5 g, 20.7 mmol, 49%) as a yellow solid.

Instead of column chromatography, product 8 can also be recrystallized from 1 CHCl3. M.P. 213-214°C (CH2Cl2); H NMR (500 MHz, Chloroform-d) δ 7.15 – 7.03 (m, 4H), 6.46 (d, J = 8.1 Hz, 2H), 4.44 (s, 4H), 4.20 (s, 2H); 13C NMR (126 MHz, CDCl3) δ 146.80, 133.99, 131.23, 127.05, 119.65, 110.64, 49.80; HRMS: + + (ES ) calculated for C14H13Br2N2 [M+H] : 366.9445, found: 366.9428; FTIR (thin film): 3404, 1594, 1490, 1314, 1266, 1180, 1119 cm-1. Characterization data matches the literature values.11

EtOOC COOEt

N Br

Br N (±)-Diethyl-2,8-dibromo-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine- 13,13-dicarboxylate 13: To a flame-dried round bottom flask equipped with a stir bar and a reflux condenser was added a solution of diazocine 12 (3.5 g, 9.57 mmol), diethyl ketomalonate (1.6 mL, 10.5 mmol) and pyridinium p- toluenesulfonate (240 mg, 0.957 mmol) in toluene (200 mL), and the reaction mixture was stirred at 110 °C for 4 hours under argon. The reaction was then cooled down to 23°C and concentrated in vacuo. Purification by column chromatography (2:1 hexanes/EtOAc) gave dibromo TB derivative 13 (4.3 g, 8.24 mmol, 86%) as a white solid. Instead of column chromatography, product 9 can also be recrystallized from MeOH. M.P. 209°C (hexanes/EtOAc); 1H NMR (500 MHz, Chloroform-d) δ 7.32 (dd, J = 8.6, 2.1 Hz, 2H), 7.20 (d, J = 8.6 Hz, 2H), 6.99 (d, J = 2.0 Hz, 2H), 4.65 (d, J = 17.7 Hz, 2H), 4.36 – 4.29 (m, 2H), 4.25 – 13 4.15 (m, 4H), 1.17 (t, J = 7.1 Hz, 6H); C NMR (126 MHz, CDCl3) δ 165.12, 146.57, 131.40, 129.30, 128.44, 127.31, 117.92, 83.01, 63.33, 56.19, 13.97; + + HRMS: (ES ) calculated for C21H21Br2N2O4 [M+H] : 522.9868, found: 522.9854; FTIR (thin film): 2980, 1754, 1475, 1267, 1201, 1119, 1019 cm-1.

EtOOC COOEt

H N N Boc Boc N N H (±)-Diethyl-2,8-bis((tert-butoxycarbonyl)amino)-6H,12H-5,11-methanodibenzo[b,f][1,5] diazocine-13,13-dicarboxylate 17: TB 13 (1.8 g, 3.49 mmol), tert- butyl carbamate (1.2 g, 10.5 mmol), Cs2CO3 (4.5 g, 14.0 mmol), Pd(OAc)2 (78 mg, 0.349 mmol) and Xantphos (400 mg, 0.698 mmol) were added to a flame- dried two-necked round bottom flask equipped with a stirrer and a reflux condenser. The flask was evacuated and back-filled with argon 3 times. Degassed dioxane (18 mL) was added to the solids and the reaction mixture was stirred for 7 h at 100°C under argon. The reaction was then cooled to 23°C, filtered through a pad of celite®, and flushed through with EtOAc. The solution was concentrated in vacuo and purification by column chromatography (2:1 to

1:1 to 1:2 hexanes/EtOAc) gave product 17 (1.4 g, 2.30 mmol, 65%) as an amorphous white solid. Instead of column chromatography, product 13 can also 1 be recrystallized from CH2Cl2/hexanes. H NMR (500 MHz, Chloroform-d) δ 7.22 (d, J = 8.7 Hz, 2H), 7.10 (s, 2H), 6.96 (dd, J = 8.7, 2.4 Hz, 2H), 6.32 (s, 2H), 4.68 (d, J = 17.6 Hz, 2H), 4.34 – 4.25 (m, 2H), 4.23 – 4.13 (m, 4H), 1.46 (s, 18H), 1.15 13 (t, J = 7.1 Hz, 6H); C NMR (126 MHz, CDCl3) δ 165.60, 152.83, 142.78, 135.07, 127.20, 126.05, 118.67, 115.90, 83.49, 80.65, 63.00, 56.66, 28.42, 13.98; + + HRMS: (ES ) calculated for C31H41N4O8 [M+H] : 597.2924, found: 597.2954; FTIR (thin film): 3348, 2978, 1726, 1530, 1159 cm-1.

EtOOC COOEt

N NH2 Boc N N H (±)-Diethyl-2-amino-8-((tert-butoxycarbonyl)amino)-6H,12H-5,11-methanodibenzo[b,f] [1,5]diazocine-13,13-dicarboxylate 18: To a round bottom flask was added 17 (200 mg, 0.336 mmol), and stirred in a mixture of TFA/CHCl3 (1:10 v/v, 15 mL) at 0°C for 3 h. TFA was quenched by carefully adding aqueous 1M NaOH (100 mL). The aqueous phase was extracted with CHCl3 (3 x 100 mL) and the combined organic layers were washed with brine (100 mL), dried over MgSO4 and concentrated in vacuo. Purification by column chromatography (2:1 EtOAc/hexanes to 100% EtOAc) gave recovered starting material (SM) 17 (120 mg, 0.201 mmol, 60%) and the product 18 (59 mg, 0.119 mmol, 35%) as a white solid. M.P. 135-138°C (hexanes/EtOAc); 1H NMR (500 MHz, Chloroform-d) δ 7.17 (d, J = 8.7 Hz, 1H), 7.05 (d, J = 8.6 Hz, 1H), 7.02 (s, 1H), 6.94 (dd, J = 8.7, 2.4 Hz, 1H), 6.48 (dd, J = 8.6, 2.5 Hz, 1H), 6.41 (s, 1H), 6.08 (d, J = 2.4 Hz, 1H), 4.61 (dd, J = 17.5, 5.0 Hz, 2H), 4.30 – 4.22 (m, 2H), 4.16 – 4.02 (m, 4H), 3.43 (s, 13 2H), 1.42 (s, 9H), 1.09 (t, J = 7.1 Hz, 6H); C NMR (126 MHz, CDCl3) δ 165.64, 165.60, 152.75, 143.27, 142.82, 138.71, 134.84, 127.26, 126.93, 126.32, 125.81, 118.50, 115.90, 115.64, 111.66, 83.42, 80.39, 62.76, 62.71, 56.42, 28.27, 13.81, + + 13.80; HRMS: (ES ) calculated for C26H33N4O6 [M+H] : 497.2400, found: + + 497.2394; (ES ) calculated for C26H32N4O6Na [M+Na] : 519.2220, found: 519.2227; FTIR (thin film): 3370, 2979, 1752, 1528, 1498 cm-1; Specific rotation 22 after chiral AD-H HPLC separation: (-)-enantiomer: [α]D = -213.4° (c = 1.0, 22 CHCl3), (+)-enantiomer: [α]D = +239.3° (c = 1.0, CHCl3).

EtOOC COOEt Br N NH2 Boc N N H (-)-Ethyl 2-amino-1-bromo-8-((tert-butoxycarbonyl)amino)-13-((ethylperoxy)- λ2-methyl)-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-13-carboxylate 19: To a stirred solution of mono-Boc Tröger’s base 18 (300 mg, 0.6 mmol) in MeCN (4.5 mL) at -20°C in a round bottom flask was added a solution of freshly recrystallized N-bromosuccinimide (17.8 mg, 0.6 mmol) in MeCN (3 mL) dropwise via a syringe pump over a period of 1 hour. The reaction was quenched with water (10 mL) and then diluted with 20 mL EtOAc. The aqueous layer was extracted using EtOAc (3 x 25 mL) and CH2Cl2 (3 x 25 mL). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated in vacuo. Purification by column chromatography (9:1 CH2Cl2/EtOAc to 1:1 CH2Cl2/EtOAc) gave product 19 (300 mg, 0.52 mmol, 86%) as an off-white solid. 1H NMR (500 MHz, Chloroform-d) δ 7.27 (d, J = 8.7 Hz, 1H), 7.13 (d, J = 8.6 Hz, 2H), 6.98 (dd, J = 8.7, 2.5 Hz, 1H), 6.67 (d, J = 8.6 Hz, 1H), 6.34 (s, 1H), 4.68 (d, J = 17.6 Hz, 1H), 4.48 (d, J = 17.9 Hz, 1H), 4.33 – 4.26 (m, 2H), 4.23 – 4.12 (m, 4H), 3.84 (s, 2H), 1.46 (s, 9H), 1.14 (td, J = 7.1, 2.4 Hz, 6H); 13C NMR (126 MHz, CDCl3) δ 165.49, 152.85, 142.88, 141.33, 139.75, 135.16, 127.23, 126.75, 126.24, 125.41, 118.79, 115.98, 115.41, 108.32, 83.28, 80.69, 63.05, 58.26, + + 56.60, 28.41, 13.98, 13.96; HRMS: (ES ) calculated for C26H32BrN4O6 [M+H] : 575.1505, found: 575.1501; FTIR (thin film): 3372, 2978, 1753, 1620, 1526, -1 22 1479, 1159 cm ; [α]D = -261.75° (c = 1.0, CHCl3).

EtOOC COOEt H N N EtOOC COOEt Boc N N N N

Boc N N H (-)-Tetraethyl-2,13-bis((tert-butoxycarbonyl)amino)-6,17-dihydro-11H,22H- 5,21:10,16-dimethanobenzo[6,7][1,5]diazocino[3,2-a]benzo[6,7][1,5]diazocino[3,2-h]phenazine-23,23,24,24-tetracarboxylate 20: To a flame-dried round bottom flask equipped with a stir bar was added Cs2CO3 (1.26 g, 3.87 mmol), and flame dried under vacuum and back-filled with argon 3 times. TB 19 (450 mg, 0.78 mmol), Pd(OAc)2 (18 mg, 0.08 mmol) and RuPhos (73 mg, 0.154 mmol) were then added and the flask was evacuated and back-filled with argon 4 times. Degassed toluene (9 mL) was added to the solid mixture and the reaction was stirred for 2 h at 110°C under argon. The reaction was then cooled to 23°C, ® filtered through a pad of celite , and flushed through with CH2Cl2 and EtOAc. The filtrate was concentrated in vacuo and purification by column chromatography

(99.5:0.5 chloroform/MeOH or 80:20 CH2Cl2/EtOAc) gave product 20 (290 mg, 0.29 mmol, 75%) as a waxy fluorescent yellow solid. 1H NMR (500 MHz, Chloroform-d) δ 7.96 (d, J = 9.3 Hz, 2H), 7.71 (d, J = 9.4 Hz, 2H), 7.37 (d, J = 8.7 Hz, 2H), 7.17 (s, 2H), 6.91 (dd, J = 8.7, 2.2 Hz, 2H), 6.29 (s, 2H), 5.00 (q, J = 18.6 Hz, 4H), 4.76 (d, J = 17.6 Hz, 2H), 4.44 (d, J = 17.7 Hz, 2H), 4.36 – 4.12 (m, 8H), 1.42 (s, 18H), 1.19 (t, J = 7.1 Hz, 6H), 1.09 (t, J = 7.1 Hz, 6H); 13C NMR (126 MHz, CDCl3) δ 165.43, 165.29, 152.76, 147.99, 142.81, 140.91, 135.18, 129.89, 129.23, 126.53, 126.45, 123.30, 118.75, 115.89, 83.65, 80.64, 63.19, 63.16, 54.93, 54.04, 28.37, 14.01, 13.98; HRMS: (ES+) calculated for + C52H59N8O12 [M+H] : 987.4252, found: 987.4222; FTIR (thin film): 3379, 2978, -1 23 1757, 1524, 1158 cm ; [α]D = -56.06° (c = 1.0, CHCl3).

EtOOC COOEt

N NH2 EtOOC COOEt N N N N

Boc N N H (-)-Tetraethyl-2-amino-13-((tert-butoxycarbonyl)amino)-6,17-dihydro- 11H,22H-5,21:10,16-dimethanobenzo[6,7][1,5]diazocino[3,2-a]benzo [6,7][1,5]diazocino[3,2-h]phenazine-23,23,24,24-tetracarboxylate 21: To a round bottom flask was added TB 20 (250 mg, 0.25 mmol), and stirred in a mixture of TFA/CHCl3 (1:10 v/v, 27.5 mL) at 0°C for 3 h. TFA was quenched by carefully adding aqueous 1M NaOH (200 mL). The aqueous phase was extracted with CHCl3 (3 x 100 mL) and EtOAc (3 x 100 mL), and the combined organic layers were concentrated in vacuo. The residue was diluted with EtOAc (100 mL), washed with brine (100 mL), dried over Na2SO4 and concentrated in vacuo. Purification by column chromatography (1:1:1 EtOAc/hexanes/CH2Cl2 for RSM; 2:1 EtOAC/CH2Cl2 for product) gave recovered SM 20 (140 mg, 0.141 mmol, 56%) and the product 21 (71 mg, 0.08 mmol, 32%) as a waxy fluorescent yellow solid. 1H NMR (500 MHz, Chloroform-d) δ 7.96 (dd, J = 9.3, 2.5 Hz, 2H), 7.72 (dd, J = 9.4, 5.6 Hz, 2H), 7.37 (d, J = 8.7 Hz, 1H), 7.27 (d, J = 8.7 Hz, 1H), 7.17 (s, 1H), 6.92 (dd, J = 8.7, 2.3 Hz, 1H), 6.53 (dd, J = 8.6, 2.4 Hz, 1H), 6.28 (s, 1H), 6.15 (d, J = 2.3 Hz, 1H), 5.08 – 4.86 (m, 5H), 4.75 (dd, J = 17.4, 14.3 Hz, 2H), 4.44 (d, J = 17.7 Hz, 1H), 4.37 – 4.14 (m, 8H), 3.43 (s, 2H), 1.42 (s, 9H), 1.21 – 13 1.17 (m, 6H), 1.09 (td, J = 7.1, 3.8 Hz, 6H); C NMR (126 MHz, CDCl3) δ 165.61, 165.42, 165.41, 165.27, 152.76, 148.17, 147.91, 143.54, 142.78, 140.99, 140.87, 140.83, 138.95, 135.16, 129.97, 129.81, 129.23, 129.05, 126.96, 126.50, 126.43, 126.40, 123.57, 123.24, 118.75, 115.89, 111.73, 83.77, 83.62, 80.61, 63.17, 63.13, 63.06, 63.06, 54.89, 54.82, 54.02, 53.93, 28.36, 13.99, 13.95; HRMS: + + (ES ) calculated for C47H51N8O10 [M+H] : 887.3728, found: 887.3729; FTIR (thin -1 22 film): 3367, 2978, 2920,1755, 1622, 1497, 1157, 1098 cm ; [α]D = -222.57° (c = 1.0, CHCl3).

EtOOC COOEt Br N NH2 EtOOC COOEt N N N N

Boc N N H (-)-Tetraethyl-2-amino-1-bromo-13-((tert-butoxycarbonyl)amino)-6,17- dihydro-11H,22H-5,21:10,16-dimethanobenzo[6,7][1,5]diazocino[3,2- a]benzo[6,7][1,5]diazocino[3,2-h] phenazine-23,23,24,24-tetracarboxylate 22: To a stirred solution of mono-Boc Tröger’s base dimer 21 (50 mg, 0.056 mmol) in MeCN (1 mL) at -20°C in a round bottom flask was added a solution of freshly recrystallized N-bromosuccinimide (10 mg, 0.056 mmol) in MeCN (0.5 mL) dropwise via a syringe pump over a period of 1 hour. The reaction was quenched with water (5 mL) and then diluted with 10 mL EtOAc. The aqueous layer was extracted using EtOAc (3 x 10 mL) and CH2Cl2 (3 x 10 mL). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated in vacuo. Purification by column chromatography (9:1 CH2Cl2/EtOAc) gave product 22 (45 mg, 0.046 mmol, 83%) as a waxy yellow solid. 1H NMR (500 MHz, Chloroform-d) δ 7.99 (t, J = 8.6 Hz, 2H), 7.75 (t, J = 8.7 Hz, 2H), 7.63 (s, 1H), 7.38 (d, J = 8.7 Hz, 1H), 7.20 (s, 1H), 6.93 (d, J = 10.9 Hz, 1H), 6.33 (s, 1H), 5.10 – 4.90 (m, 4H), 4.77 (d, J = 17.7 Hz, 1H), 4.52 – 4.40 (m, 3H), 4.37 – 4.15 (m, 8H), 1.42 (s, 9H), 1.21 (dt, J = 14.0, 7.1 Hz, 6H), 1.10 (td, J 13 = 7.1, 3.6 Hz, 6H); C NMR (126 MHz, CDCl3) δ 165.39, 165.27, 165.15, 164.87, 152.81, 148.09, 147.78, 142.76, 141.04, 140.95, 140.92, 140.76, 139.76, 139.57, 135.17, 130.07, 129.77, 129.54, 129.22, 128.97, 126.53, 126.47, 125.85, 123.30, 123.10, 115.95, 108.22, 107.73, 83.62, 83.28, 80.74, 63.44, 63.37, 63.25, 63.22, 56.53, 54.91, 54.24, 54.03, 28.37, 14.03, 14.00; HRMS: (ES+) calculated for + C47H50BrN8O10 [M+H] : 965.2833, found: 965.2818; FTIR (thin film): 3379, 2922, -1 22 2858,1757, 1460, 1158, 1100 cm ; [α]D = -65.07° (c = 1.0, CHCl3).

O TMSO OTMS

2,2,8,8-tetramethyl-3,7-dioxa-2,8-disilanonan-5-one 30: To a stirred solution of dihydroxy acetone dimer (20 g, 111.0 mmol) and triethylamine (65.1 mL, 466.5 mmol) in dichloromethane (200 mL) at 0°C was added trimethylsilyl chloride (56.4 mL, 444 mmol) dropwise via a syringe pump over a period of 2 hours. The reaction mixture was then warmed to 23°C was stirred for 4 hours. The white precipitate in the reaction mixture was filtered off, and the filtrate was washed with saturated NaHCO3 solution (100 mL). The aqueous layer was extracted with petroleum ether (3 x 50 mL) and concentrated in vacuo. Purification by distillation (56-58°C/2.0 mmHg) gave product 30 (37g, 0.158 mmol, 71% yield) as a colorless liquid. 1H NMR (500 MHz, Chloroform-d) δ 4.36 (s, 4H), 0.13 (s, 18H); 13 + C NMR (126 MHz, CDCl3) δ 208.57, 67.19, -0.50; HRMS: (ES ) calculated for

+ C9H22O3Si2Na [M+Na] : 257.1005, found: 257.1011; FTIR (thin film): 2958, 2900, 1741, 1252, 1100 cm-1

TMSO OTMS 2,2,8,8-tetramethyl-5-methylene-3,7-dioxa-2,8-disilanonane 31: To a flame- dried round bottom flask were added methyltriphenylphosphonium bromide (45.8 g, 128.1 mmol) and sodium hydride (3.08 g, 128.1 mmol) in anhydrous tetrahydrofuran (200 mL), and the mixture was stirred at 70°C for 2 h under argon. The reaction mixture was cooled to 10°C, followed by dropwise addition of a solution of 30 (30 g, 128.1 mmol) in dry tetrahydrofuran (50 mL) over a period of 30 minutes. The reaction mixture was warmed to 23°C and stirred for 12 h. The red precipitate was filtered through a celite pad via vacuum filtration and washed with cold petroleum ether. The filtrate was concentrated in vacuo, and purification by distillation (42-45°C /2.0 mmHg) gave product 31 (14 g, 60.2 mmol, 47%) as a colorless liquid. 1H NMR (500 MHz, Chloroform-d) δ 5.10 – 5.07 13 (m, 2H), 4.13 (t, J = 1.2 Hz, 4H), 0.12 (s, 18H); C NMR (126 MHz, CDCl3) δ + 147.62, 110.21, 63.48, -0.33; HRMS: (ES ) calculated for C10H24O2Si2Na [M+Na]+: 255.1213, found: 255.1212; FTIR (thin film): 2958, 2899, 2863,1252, 1081 cm-1

O O

(7S,10R)-7-isopropyl-10-methyl-3-methylene-1,5-dioxaspiro[5.5]undecane 32: To a stirred solution of bis(trimethylsilyl) ether 31 (2.52 g, 10.85 mmol) and l- menthone (01.79 mL, 10.34 mmol) in CH2Cl2 (7 mL) at -78°C was added freshly distilled TMSOTf (0.15 mL, 0.827 mmol) dropwise over 5 minutes, and the resulting solution was stirred at -78°C for 24 h under Argon. The reaction was quenched by the successive additions of pyridine (2.3 mL) and 0.5% NaOH in methanol (15 mL), and the reaction mixture was stirred at room temperature for 1 h. Water (10 mL) was added to the reaction and the aqueous layer was extracted with petroleum ether (3 x 25 mL). The combined organic layers were washed with water (2 x 25 mL) and brine, dried over Na2SO4, and concentrated in vacuo to give clean product 32 as yellow oil (2.32 g, 10.34 mmol, quantitative yield) (Column chromatography in 2% diethyl ether/hexanes, if needed). 1H NMR (500 MHz, Benzene-d6) δ 4.54 (d, J = 8.6 Hz, 2H), 4.37 (d, J = 13.3 Hz, 1H), 4.14 (d, J = 13.5 Hz, 1H), 4.07 (d, J = 13.3 Hz, 1H), 3.98 (d, J = 13.5 Hz, 1H), 2.75 (hept d, J = 7.0, 2.2 Hz, 1H), 2.52 (ddd, J = 13.5, 3.4, 2.0 Hz, 1H), 1.69 – 1.50 (m, 4H), 1.38 (ddd, J = 12.6, 4.0, 2.3 Hz, 1H), 1.14 (d, J = 6.9 Hz, 3H), 1.05 (d, J = 7.1 Hz, 3H), 0.85 (d, J = 6.7 Hz, 3H), 0.80 (dd, J = 12.1, 4.2 Hz, 1H), 0.73 (t, J = 12.7 Hz, 13 1H); C NMR (126 MHz, C6D6) δ 141.31, 107.84, 100.51, 63.77, 63.44, 51.73, 38.26, 35.35, 29.49, 24.95, 24.19, 22.83, 22.46, 19.41; HRMS: (ES+) calculated + for C14H24O2Na [M+Na] : 247.1674, found: 247.1682; FTIR (thin film): 3074,

-1 23 2952, 2869, 2845, 1456, 1310, 1155, 1111 cm ; [α]D = -21.32° (c = 1.0, CHCl3).

O O

O (7S,10R)-7-isopropyl-10-methyl-1,5-dioxaspiro[5.5]undecan-3-one 27: A stirred solution of 32 (1.7 g, 7.58 mmol) in MeOH (150 mL) at -78°C was bubbled with O3 until the blue color persisted for more than 2 minutes. The excess O3 was then removed by allowing O2 to bubble through the solution for 20 minutes. Dimethyl sulfide (3.34 mL, 45.46 mmol) was added dropwise and the mixture was allowed to stir and to warm to 23°C over 3 h. The reaction mixture was concentrated in vacuo, and purification by column chromatography (2-5% Et2O/petroleum ether) gave product 27 (1.2 g, 5.3 mmol, 71%) as a pale yellow oil. 1H NMR (500 MHz, Chloroform-d) δ 4.35 (s, 2H), 4.29 – 4.18 (m, 2H), 2.37 (hept d, J = 6.9, 1.5 Hz, 1H), 2.21 (ddd, J = 13.7, 3.5, 2.0 Hz, 1H), 1.76 (m, 1H), 1.65 – 1.52 (m, 2H), 1.49 – 1.38 (m, 2H), 1.00 (dd, J = 13.7, 12.6 Hz, 1H), 0.93 (d, J = 7.0 Hz, 3H), 0.92 (d, J = 3.6 Hz, 3H), 0.91 (d, J = 3.8 Hz, 3H), 0.89 – 0.83 13 (m, 1H); C NMR (126 MHz, CDCl3) δ 207.46, 101.55, 68.74, 67.98, 51.42, 40.33, 34.73, 29.75, 24.66, 23.83, 22.53, 22.17, 18.74; HRMS: (ES+) calculated + for C13H23O3 [M+H] : 227.1647, found: 227.1643; FTIR (thin film): 2953, 2871, -1 23 1746, 1457, 1157, 1125, 1054 cm ; [α]D = -5.97° (c = 1.05, CHCl3).

O O

Br N

N Br (±)-(2S,5R)-2'',8''-dibromo-2-isopropyl-5-methyl-6''H,12''H-dispiro[cyclo- hexane-1,2'-[1,3]dioxane-5',13''-[5,11]methanodibenzo[b,f][1,5]diazocine] 33: To a flame-dried flask were added diazocine 12 (2.44 g, 6.627 mmol), spiroketone 27 (1.5 g, 6.627 mmol) and AlCl3 (88.4 g, 0.66 mmol) in CH2Cl2 (12.5 mL), and the reaction mixture was stirred at 23°C for 12 h under argon. The reaction was quenched with pH=7 phosphate buffer (20 mL), and the aqueous phase was extracted with CH2Cl2 (3 x 25 mL). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated in vacuo. Purification by column chromatography (5% Et2O/petroleum ether) gave two diastereomers of product 33 ((-)-diastereomer: 1.22 g, 2.11 mmol, 32%; (+)-diastereomer: 1.44 g, 2.49 mmol, 38%) as white solids. (-)-diastereomer: 1H NMR (500 MHz, Chloroform-d) δ 7.28 (td, J = 8.4, 2.2 Hz, 2H), 7.05 (d, J = 8.6 Hz, 1H), 7.02 (d, J

= 2.2 Hz, 1H), 6.97 (d, J = 2.2 Hz, 1H), 6.93 (d, J = 8.6 Hz, 1H), 4.74 (d, J = 17.5 Hz, 1H), 4.36 (d, J = 17.4 Hz, 1H), 4.14 (d, J = 17.5 Hz, 1H), 3.96 (d, J = 17.5 Hz, 1H), 3.90 – 3.83 (m, 3H), 3.80 (dd, J = 11.3, 1.8 Hz, 1H), 2.69 (d, J=17.5 Hz, 1H), 2.65 – 2.57 (m, 1H), 1.71 (d, J = 11.9 Hz, 1H), 1.58 –1.25 (m, 4H), 0.97 (d, J = 1.6 Hz, 3H), 0.96 (d, J = 1.2 Hz, 3H), 0.90 (d, J = 6.6 Hz, 3H), 0.86 (m, 1H), 0.69 13 (t, J = 13.0 Hz, 1H); C NMR (126 MHz, CDCl3) δ 146.76, 146.49, 131.26, 131.10, 130.34, 129.51, 129.37, 129.01, 128.64, 127.78, 117.38, 116.84, 100.60, 66.51, 63.27, 62.91, 54.31, 54.17, 51.07, 36.51, 35.04, 29.53, 24.87, 23.78, + + 22.37, 22.10, 18.96; HRMS: (ES ) calculated for C27H33Br2N2O2 [M+H] : 575.0909, found: 575.0912; FTIR (thin film): 2951, 2867, 1472, 1400, 1300, -1 23 1101 cm ; [α]D = -91.05° (c = 1.00, CHCl3).

(+)-diastereomer: 1H NMR (500 MHz, Chloroform-d) δ 7.28 (ddd, J = 16.9, 8.5, 1.6 Hz, 2H), 7.07 (d, J = 8.6 Hz, 1H), 7.02 (d, J = 2.2 Hz, 1H), 6.98 (d, J = 1.9 Hz, 1H), 6.93 (d, J = 8.6 Hz, 1H), 4.71 (d, J = 17.5 Hz, 1H), 4.37 (d, J = 17.4 Hz, 1H), 4.12 (d, J = 17.5 Hz, 1H), 4.06 (d, J = 11.3 Hz, 1H), 3.96 (d, J = 17.5 Hz, 1H), 3.86 (dd, J = 12.9, 3.7 Hz, 1H), 3.80 (dd, J = 11.3, 3.6 Hz, 1H), 3.67 (d, J = 12.9 Hz, 1H), 2.69 (d, J = 12.7 Hz, 1H), 2.64-2.50 (m, 1H), 1.71 (d, J = 12.5 Hz, 1H), 1.58 – 1.24 (m, 4H), 1.02 (d, J = 6.9 Hz, 3H), 0.93 (d, J = 7.1 Hz, 3H), 0.88 (d, J = 6.6 Hz, 3H), 0.83 (m, 1H), 0.70 (t, J = 13.1 Hz, 1H); 13C NMR (126 MHz, CDCl3) δ 146.78, 146.51, 131.26, 131.07, 130.35, 129.54, 129.27, 129.05, 128.72, 127.76, 117.34, 116.84, 100.77, 66.56, 63.23, 63.08, 54.34, 54.05, 50.98, 36.56, 35.02, 29.37, 24.82, 23.86, 22.42, 22.31, 19.27; HRMS: (ES+) + calculated for C27H33Br2N2O2 [M+H] : 575.0909, found: 575.0909; FTIR (thin -1 23 film): 2950, 2868, 1473, 1401, 1299, 1169, 1121, 1100 cm ; [α]D = 65.99° (c = 1.00, CHCl3).

OH OH

Br N

N Br (+)-(2,8-dibromo-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-13,13- diyl)dimethanol 34: To a round bottom flask were added the (+) diastereomer of 33 (200 mg, 0.347 mmol) and p-TsOH (24 mg, 0.069 mmol) in a mixture of MeOH/CH2Cl2 (10:1 v/v, 5 mL), and the reaction mixture was stirred at 23°C for 16 h. The reaction was quenched using saturated NaHCO3 (10 mL), and the aqueous phase was extracted with CH2Cl2 (3 x 20 mL). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated in vacuo, Purification by column chromatography (2.5% MeOH/CH2Cl2) gave product 34 (122 mg, 0.277 mmol, 80% ) as a white solid.1H NMR (500 MHz, Chloroform-d) δ 7.30 (dd, J = 8.6, 2.2 Hz, 2H), 7.05 – 7.01 (m, 4H), 4.57 (d, J = 17.5 Hz, 2H), 4.05 (d, J = 17.5 Hz, 2H), 3.91 (d, J = 11.6 Hz, 2H), 3.83 (d, J = 11.6 Hz, 2H), 13 2.70 (s, 2H); C NMR (126 MHz, CDCl3) δ 146.45, 131.29, 130.19, 129.44, + 128.00, 117.58, 73.77, 63.61, 54.80; HRMS: (ES ) calculated for C17H17Br2N2O2

[M+H]+: 438.9657, found: 438.9653; FTIR (thin film): 3375, 2922, 1474, 1199, -1 22 1168, 1120, 1077 cm ; [α]D = 86.12° (c = 1.00, CHCl3). For diol product using (- 22 )-33: [α]D = -93.51° (c = 1.00, CHCl3).

Measurement of association constant between bis-Boc dimer 20 and hydroquinone: A solution of bis-Boc dimer 20 (2 mg, 0.002 mmol) was prepared in a mixture of 2:1 THF-d8: D2O (0.6 mL, v/v). Another solution was made by dissolving five equivalents of hydroquinone (1.1 mg, 0.10 mmol) in 200 µL of 2:1 THF-d8: D2O. The hydroquinone solution was then titrated into the bis-Boc dimer solution (50 µL of hydroquinone each time), and 1H-NMR spectra were recorded. To fit the association constant (Ka) of the complex, a 1:1 binding stoichiometry was assumed. For the fitting of the association constants, the concentrations of both the bis-Boc dimer 20 and hydroquinone were listed, together with the corresponding 1H NMR chemical shifts of representative protons. The data was then entered into the software package DynaFit, which was used to determine the association constant and the corresponding standard error by fitting to all representative 1 H NMR resonances at the same time. The keyword “titration” was used while performing DynaFit calculations, which accurately accounts for the dilution effects of titration experiments.

RESULTS AND DISCUSSION

SYNTHESIS OF TB HELICAL SCAFFOLDS

The first step in the synthesis of the TB monomer 13 was the reaction of 4- bromoaniline and formaldehyde under acidic conditions to form dibromo TB monomer 11 in 75% yield.7 In order to remove the methylene bridge, TB 11 was reacted with TFAA in DCM followed by treatment with base (NaOH) to give diazocine 12 in 53% yield.11 The yields of TB monomer 11 and diazocine 12 were similar to the reported literature yields. To install the diester bridge functionality, diazocine 12 was heated at reflux in toluene with diethyl ketomalonate and pyridinium tosylate to give the diester TB monomer 13 in 81% yield (Scheme 2).

TB monomer 13 was very soluble in a variety of organic solvents like DCM, chloroform, benzene, toluene, i-PrOH, EtOH, THF and ethyl acetate. A stability study was done by Dr. Rosa Cookson, a postdoc in the lab, comparing the stability of TB monomer 13 vs. TB monomer 11. Both the monomers were treated with different reagents known to result in opening of the TB bridge. These reagents can either result in the opening of the TB bridge to form diazocine 12, or may lead to decomposition of the starting material (SM) (Table 1).11 It was found that diester TB 13 is much more stable TB 11, which was consumed in 5 minutes with TFAA, and in 1 h with concentrated HCl and TFA. On the other hand, TB 13 did not show any ring opening and 100% SM was recovered from all the three conditions.

Scheme 2. Synthesis of methylene TB 117, diazocine 1211 and Diester TB monomer 13

1) TFAA, DCM N NH2 (CH2O)n Br 25°C, 2h TFA 2) NaOH, EtOH Br Br -15°C → 25°C, 36h N 25°C, 16h 75% 53% 11

EtOOC COOEt HN Br Diethylketomalonate, PPTS N Br

Br N Toluene, H 110°C, 4h Br N 81% 12 13

Table 1. Stability study of diester TB 13 compared to methylene TB 11a

Reaction conditions

TB TFAA, CH2Cl2, 23°C Conc. HCl, NaNO2, TFA, NaNO2, H2O, H2O, 23°C 0°C

11 100% consumption No SM after 1 hour No SM after 1 hour after 5 min 13 100% recovered SM, 100% recovered SM, 100% recovered SM, 12 hours 12 hours 12 hours aAll of the reaction conditions use highly acidic mediums, which are known to either open the TB bridge of methylene TB compounds or lead to decomposition of the starting material.

EtOOC COOEt

N EtOOC COOEt N N N N

N 14

Figure 10. Energy minimized Web MO model of the TB dimer 14.

EtOOC COOEt

EtOOC COOEt N N N N EtOOC COOEt N N N N

N 2 15

15’

15’’

Figure 11. Energy minimized Web MO models of A) 15’, top view of diester TB tetramer 15; B) 15’’, side view of 15.

Once it was established that diester TB had improved stability and solubility properties, we modeled the diester dimer 14 (Figure 10). It was seen that the TB dimer 14 still forms a chiral binding cleft. We also modeled the diester TB

tetramer 15 (Figure 11) and octamer 16 (Figure 12) in Web MO (Gaussian-PM3) to confirm if these oligomers still retain their helical shape. It was seen that the TB tetramer 15 and the octamer 16 maintain their helicity in the presence of the diester bridge.

EtOOC COOEt

COOEt EtOOC N N N N EtOOC COOEt N N N N

N 6 16

16’

16’’

Figure 12. Energy minimized Web MO models of A) 16’, top view of diester TB octamer 16 and B) 16’’, side view of 16.

The next step in the synthesis involved replacing the bromine of TB 13 with the diamine functionality. This was achieved by a Buchwald-Hartwig coupling between TB 13 and tert-butyl carbamate, using Pd(OAc)2 as the palladium source and Xantphos as the ligand in toluene. The Buchwald-Hartwig coupling gave bis-Boc diester TB 17 in 65% yield (Scheme 3). Bis-Boc diester TB 17 then was treated with trifluoroacetic acid in CHCl3 at 0°C for 3 h to perform a selective deprotection of the Boc group 12 and synthesize the mono-Boc TB 18. The observed product to recovered SM ratio was consistently 1:2 (30% product, 65% recovered SM). Multiple cycles were done in order to get a reasonable amount of mono-Boc TB 18 (75% overall yield after 4 cycles). If the reaction is stirred for more than 3 h, the other N-Boc group also gets removed and formation of diamine product is seen.

Scheme 3. Synthesis of Diester TB monomer 17 and 18, and chiral resolution of diester TB monomer 18

EtOOC COOEt EtOOC COOEt Xantphos, H2NBoc, Cs CO , Pd(OAc) H N Br 2 3 2 N N Boc 1,4-dioxane Boc Br N 100°C, 6h N N 65% H 13 17

EtOOC COOEt TFA/CHCl3 (1:10) N Semiprep Chiral AD-H NH2 (+) and (-) 0°C, 3h 60:40:0.1 enantiomers 30% product Boc Hexanes/i-PrOH/DEA N N 65% RSM H 99% 18

As mentioned in the introduction, enantiomerically pure monomer was required to synthesize the syn TB oligomers via the double Buchwald-Hartwig phenazine synthesis. Hence, the chiral resolution of one of TB monomer 13, 17 or 18 was crucial. It is well known in literature that racemic TB derivatives with the methylene bridge can be easily resolved by forming diastereomeric salts with (+)- dibenzoyl-D-tartaric acid ((+)-DBTA).13 Based on this, we tried to resolve the diester TB 13, 17 and 18 using (+)-DBTA in several solvents like dichloroethane, CH2Cl2, THF, CH3CN, acetone, toluene and Et2O. However, all the attempts to resolve the racemic diester TB derivatives were unsuccessful. Other chiral Lewis acids like (1S)-(+)-camphorsulfonic acid14, (R)-BINOL15 and binaphthalenediyl hydrogen phosphate16 were also investigated. While some of these chiral Lewis acids led to the formation of precipitate, no chiral resolution was observed through analytical chiral HPLC. (The chiral resolution work described above was done by Dr. Rosa Cookson). Since none of the above experiments yielded any

successful resolution, we decided to separate the mono-Boc diester TB 18 by HPLC using chiral AD-H column. The conditions used for the semiprep column were 60:40:0.1 hexanes/isopropyl alcohol/diethyl amine at a flow rate of 15 mL/min for 17 minutes, with a loading of 40 mg (400 µL of a 100 mg/mL solution) in each run. For the analytical column, the flow rate was 1ml/min with a loading of 20 µL of a 1 mg/mL solution. Once we had enantiopure mono-Boc (-)-diester TB 18, it was treated with N-bromo succinimide in MeCN at -20°C to give (-)-bromo aniline TB 19 in 85% yield. Bromoaniline TB 19 was then used to perform the double Buchwald Hartwig coupling to synthesize the dimer via the formation of a 9 phenazine ring. Bromo aniline TB 19 was treated with RuPhos, Pd(OAc)2 and Cs2CO3 in anhydrous degassed toluene at reflux to form the diester bis-Boc TB dimer 20 in 75% yield (Scheme 4).

Scheme 4. Synthesis of bromoaniline Diester TB 19 and bis-Boc diester TB dimer 20 (Note: TB oligomers 18, 19 and 20 are drawn as one enantiomer for clarity. However, the stereochemistry is unknown)

COOEt EtOOC COOEt EtOOC Br NBS N N NH2 NH2 MeCN Boc Boc -20°C, 1h N N N N H 85% H (-) (-) 18 19

EtOOC COOEt RuPhos, H N N Cs2CO3, Pd(OAc)2 EtOOC COOEt Boc Toluene N 110 C, 2h N ° N 75% N Boc N N H (-) 20

After synthesizing the syn dimer 20, we decided to proceed towards the synthesis of the tetramer (Scheme 5). Bis-Boc TB dimer 20 was treated with trifluoroacetic acid in CHCl3 at 0°C for 3 hours to selectively deprotect one of the Boc groups and synthesize the mono-Boc TB dimer 21. We also observed a consistent product to recovered SM ratio of about 1:2. Multiple cycles were done in order to get a reasonable yield of mono-Boc TB dimer 21. Mono-Boc dimer 21 was then reacted with N-bromo succinimide in MeCN at -20°C to give (-)-bromo aniline TB dimer 22. Several attempts were made to achieve the double

Buchwald-Hartwig coupling using RuPhos, Pd(OAc)2 and Cs2CO3 in toluene at 110°C to form the tetramer 23. But, no product formation was seen and only SM was seen. The reaction was even attempted at elevated temperatures (150°C- 180°C). However, no product formation was seen and all the SM decomposed in 3 hours (150°C). This result may be a consequence of the conformation of the dimer 22, which is inhibiting the formation of the phenazine ring.

Scheme 5. Synthesis of mono-Boc TB dimer 21, bromoaniline TB dimer 22 and proposed tetramer 23

EtOOC COOEt EtOOC COOEt H N N N EtOOC COOEt Boc NH2 EtOOC COOEt N TFA/ CHCl3 N N N N (1:10) N N N Boc 0°C, 3h N N 30% Product, Boc H (-) N N 60% RSM H (-) 20 21

EtOOC COOEt Br N NH Buchwald- Hartwig NBS 2 EtOOC COOEt Coupling MeCN N N -20°C, 1h N 75% N Boc N N H (-) 22

EtOOC COOEt

H N N Boc EtOOC COOEt N N N N EtOOC COOEt N N N N

Boc N N H 2 23

PRELIMINARY BINDING STUDIES WITH HYDROQUINONE

In order to determine if it was possible to bind a substrate in the binding cleft of the syn bis-Boc dimer 20, preliminary binding studies were attempted, using hydroquinone as the binding substrate. The goal was to determine if an association constant (Ka) could be determined for possible interactions between

the binding cleft of the bis-Boc dimer 20 and hydroquinone, through π-π stacking or hydrogen bonding. The study was done by titrating hydroquinone into a

1 2

3 4

Figure 13. 1H NMR peak shifts for syn dimer (graph 1,2,3 and 4) and hydroquinone (graph 5), with the increasing concentration of hydroquinone in 2:1 THF-d8/D2O.

solution of dimer 20, and analyzing the observed changes in the 1H NMR chemical shifts of both the syn dimer 20 and hydroquinone, with the increasing concentration of hydroquinone (Figure 12). This data was then analyzed using -1 Dynafit and the binding constant Ka was found to be 43±15M .

MENTHONE-BASED CHIRAL AUXILIARY FOR BETTER SEPARATION OF ENANTIOMERS

One of the biggest challenges in the synthesis of Tröger’s base dimer 20 was the chiral resolution of the monomer 18. Though we were able to separate the two enantiomers successfully using a chiral AD-H semiprep column, we sought the easiest and the most efficient way to do it. Chiral columns are very expensive and everyone might not have access to them. Moreover, the maximum loading for each run is only 40-50 mg of substrate, and hence it takes multiple runs to separate even a gram of the material. This makes the process solvent intensive, since each run requires around 300-400 mL of solvent.

Scheme 6. Proposed synthesis of menthone-based chiral auxiliary 27

1) Trizma. HCl CH(OMe)3 p-TsOH

p-TsOH 2) NEt3 O O O

24 25

NaIO4, KH2PO4 O O O O H2O

H2N OH O 27 26

In an effort to overcome this problem, we devised a synthesis using a menthone- based chiral auxiliary. We reasoned that the chirality of the auxiliary could be utilized to selectively form only one diastereomer of TB 33 by asymmetric induction. Even if no asymmetric induction is observed, it would still result in the formation of a pair of diastereomers, which would be readily separable by column chromatography. The design of the chiral auxiliary was based on work done by Martin Demuth and coworkers in the 1980s, where they used menthone-based dioxacyclohexenones to perform selective [2+2] photocycloadditons with olefins.17

We proposed a synthesis (Scheme 6) based on literature precedent.18 According to the proposed synthesis, l-menthone 24 is reacted with trimethyl orthoformate and MeOH in the presence of p-TsOH to form the menthone dimethoxy ketal 25, followed by reaction with tris(hydroxymethyl)aminomethane hydrochloride and NEt3 to form spiro compound 26, which on oxidation with NaIO4 would give access to menthone chiral auxiliary 27. Treatment of l-menthone 24 with ketalization conditions led to the formation of a mixture of desired trans-ketal 25 and undesired cis-ketal 28 in a 1:1 ratio. The undesired cis-menthone ketal 28 arose from epimerization of l-menthone at the α-position (Scheme 7). The formation of epimers was confirmed by comparing the NMR spectrum with the literature data. 19 Reaction conditions were changed to 23°C to prevent the epimerization. However, the reaction was very slow and still showed the formation of the undesired product. Separation of the epimers was tried via distillation (50-53°C, 2 mmHg), but did not yield any successful results.

Scheme 7. Ketalization of menthone 24, to form trans-menthone ketal 25, and undesired cis-menthone ketal 28

CH(OMe)3 + p-TsOH, MeOH O reflux, 16h O O O O

24 25 28 1:1 mixture of epimers

One of the well-known ways in the literature to prevent epimerization of ketones is the Noyori acetalization of ketones with TMS protected bis-ethers. 20 We decided to synthesize our menthone chiral auxiliary 27 using this route. The first step towards the synthesis of menthone chiral auxiliary was the reaction of dihydroxy acetone dimer 29 with TMSCl in presence of base NEt3 to form bis(trimethylsilyloxy) ether 30 (Scheme 8). A Wittig reaction of 30 with methyltriphenyl phosphonium bromide formed the bis(trimethylsilyloxy) vinyl ether 31. The next step was the Noyori acetalization of menthone with vinyl ether 31, in presence on TMSOTf.21 The reaction gave methylene spiroketal 32 in quantitative yield when it is stirred at -78°C for 24 hours. It is to be noted that formation of menthone epimers was seen along with unreacted SM and product when the reaction warmed to 23°C after stirring -78°C for 10 hours. In order to form product without epimerization, it is necessary to let the reaction go to completion with no SM remaining for 24 h at -78°C. Finally, ozonolysis of methylene spiroketal 32 gave the desired menthone chiral auxiliary 27 in 72% yield.22

Scheme 8. Synthesis of menthone-based chiral auxiliary 2721,22

OH TMSCl, NEt O OH 3 PPh3CH3 Br O

HO CH Cl TMSO OTMS O 2 2 NaH, THF OH 25°C, 2h 10°C, 3h

29 72% 30 56%

O , DMS O 3 TMSO OTMS O O TMSOTf MeOH -78°C, 30 min CH2Cl2 31 -78°C, 24h 72% quantitative 32

O O

O 27

Once we made menthone chiral auxiliary 27, the next step was to make the Tröger’s base diastereomers. Menthone auxiliary 27 was reacted with diazocine 12 using AlCl3 as the Lewis acid to form menthone Tröger’s base 33 (Scheme 9). The NMR of crude TB 33 showed interesting results, and the diastereomer formation was seen in a 1.3: 1 ratio. TLC of TB 33 showed the diastereomers of product as two separate spots, and were easily separated using column chromatography (5% Et2O/petroleum ether, Rf of diastereomers = 0.3 and 0.4 in 10% Et2O/petroleum ether). We also decided to screen different Lewis acid to further explore if one of the diastereomers could be formed preferentially over the other. The reactions were stirred for 24 h at 23°C using 10 mol% catalyst loading (Table 2). 1H NMR showed that the reaction did not go to completion using TiCl2(OiPr)2, molecular sieves, no catalyst and Al(OiPr)3. The diastereomeric ratio for these reactions stayed in the range of 1:1.3 to 1:1.4. With TiCl4, TiCl2(S- BINOL), AlCl3 and TiCl2(OiPr)2, the reaction went to completion. Chiral catalyst TiCl2(S-BINOL) showed promising results with a diastereomeric ratio of 1:3. However, TiCl2(S-BINOL) is not commercially available and is difficult to 23,24 synthesize. The results varied with each batch of TiCl2(S-BINOL) and were not reproducible.

Scheme 9. Synthesis of menthone TB monomer 27 and diol TB 34

OH OH

O O p-TsOH

MeOH/CH Cl 2 2 Br N (10:1) Br N 23°C, 16h 94% N Br Br NH Br N (-)-34 (-)-33 HN Br 8

AlCl3, Dichloroethane 23°C, 12h O O

(-)-diastereomer- 36% OH OH O (+)-diastereomer- 47% 27 O O p-TsOH MeOH/CH Cl 2 2 N (10:1) Br Br N 23°C, 16h 80% N Br N Br (+)-34 (+)-33

Table 2. Lewis Acid Screen for diastereoselectivity in the formation of menthone TB 33a

Catalyst Diastereomeric ratio by Product: Starting Material (SM) 1H NMR

TiCl2(OiPr)2 1.4: 1 100% product, No SM

Ti(OiPr)4 1.4: 1 90% product, 10% SM

TiCl4 1.3: 1 100% product, No SM

TiCl2(S-BINOL) 3.0: 1 100% product, No SM No catalyst* 1.3: 1 30% product, 70% SM Mol. Sieves* 1.3: 1 40% product, 60% SM

AlCl3 1.3: 1 100% product, No SM

Al(OiPr)3 1.4: 1 40% product, 60% SM aAll the reactions were run using 10 mol% of the catalysts at 23°C for 24h. All the reactions (excluding *) were quenched with pH 7 phosphate buffer.

No further experiments were done to explore the diastereomeric ratio of product formation. However, the inherent induction in the ratio of 1:1.4 is still interesting and gives access clean diastereomers via column chromatography.

CONCLUSION AND FUTURE WORK

During this project, we were able to synthesize the diester TB monomer 13, which is highly soluble in most organic solvents like solvents like DCM, chloroform, benzene, toluene, i-PrOH, EtOH, THF and ethyl acetate, unlike the conventional methylene bridged TB 11. It was also established via a stability study that diester TB 13 is much more stable to acidic conditions in terms of bridge opening and decomposition, compare to methylene TB 11. The more soluble diester TB 13 led to easy synthesis of syn diester TB dimer 20 using double Buchwald-Hartwig coupling based phenazine formation. This syn TB dimer 20 has a potential binding cleft, as shown by energy minimization models in Web MO, and can be used to form the tetrameric and octameric helical scaffolds. Preliminary binding studies between syn dimer 20 and hydroquinone showed promising results, and the value of association constant (Ka) was found to be 43±15M-1 using DynaFit. Similar binding studies can be conducted to determine the association constants for the tetramer and the octamer, with different binding substrates. The synthesis of menthone-based chiral auxiliary 27 provides an effective way to separate the diastereomers using column chromatography and gain access enantiopure TB monomers. It was also interesting to see the inherent diastereomeric selectivity of 1.3:1 in the formation of menthone TB 33, which can be explored further to synthesize enantiomerically pure TB monomers via asymmetric induction.

The synthesis of TB-derived oligomeric structures provides a new template for the synthesis of non-peptide helical scaffolds, the dimensions of which can be controlled by judicious choice of the starting monomer. These spatially addressable well-defined TB helical structures will provide important advantages over the more conformationally flexible helix mimetics reported to date. Further studies remain to be done towards the synthesis of the tetrameric and octameric helical systems. After these helical compounds are synthesized, their applications in molecular recognition, inhibition of PPIs and design of chiral catalysts can be explored.

REFERENCES

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16. Wilen, S. H.; Qi, J. Z.; Williard, P. G. Resolution, asymmetric transformation, and configuration of Troeger's base. Application of Troeger's base as a chiral solvating agent. J. Org. Chem. 1991, 56 (2), 485-487. 17. Demuth, M.; Palomer, A.; Sluma, H.D.; Dey, A. K.; Krüger, C.; Tsay, Y. H. Asymmetric Photocycloadditions with Optically Pure, Spirocyclic Enones. Simple Synthesis of (+)- and (−)-Grandisol. Angew. Chem. Int. Ed. Engl. 1986, 25 (12), 1117–1119. 18. Craig, R. A.; Roizen, J. L.; Smith, R. C.; Jones, A. C.; Stoltz, B. M. Enantioselective Synthesis of a Hydroxymethyl-cis-1,3-cyclopentenediol Building Block. Org. Lett. 2012, 14 (22), 5716–5719. 19. Taskinen, E. Cyclohexanone Dimethyl Acetals: A 13C NMR, Thermodynamic, and Ab Initio Study. Struc. Chem. 1998, 9 (6), 411-418. 20. Noyori, R.; Murata, S.; Suzuki, M. Trimethysilyl triflate in organic synthesis. Tetrahedron 1981, 37 (23), 3899–3910. 21. Harada, T.; Hayashiya, T.; Wada, I.; Iwa-ake, N.; Oku, A. Enantioselective Functionalization of Prochiral Diols via Chiral Spiroketals: Preparation of Optically Pure 2-Substituted 1,3-Propanediol Derivatives and Asymmetric Synthesis of Chroman Ring and Side Chain of α –Tocopherol. J. Am. Chem. Soc. 1987, 109, 527-532. 22. Harada, T.; Nakajima, H.; Ohnishi, T.; Takeuchi, M.; Oku, A. A General Method for the Preparation of Enantiomerically Pure 2-Substituted Glycerol Derivatives by Utilizing l-Menthone as a Chiral Template. J. Org. Chem. 1992, 57, 720-724. 23. Mikami, K.; Terada, M.; Nakai, T. Catalytic asymmetric glyoxylate-ene reaction: a practical access to .alpha.-hydroxy esters in high enantiomeric purities. J. Am. Chem. Soc. 1990, 112, 3949-3954. 24. Posner, G. H.; Dai, H.; Bull, D. S.; Lee, J.K.; Eydoux, F.; Ishihara, Y.; Welsh, W.; Pryor, N.; Petr, S. Lewis Acid-Promoted, Stereocontrolled, Gram Scale, Diels−Alder Cycloadditions of Electronically Matched 2- Pyrones and Vinyl Ethers: The Critical Importance of Molecular Sieves and the Temperature of Titanium Coordination with the Pyrone. J. Org. Chem. 1996, 61 (2), 671–676.

31 APPENDICES rg-01-80_pure.2.ﬁd 7.260 CDCl3 7.105 7.089 7.084 6.466 6.450 4.444 4.200

NH Br

Br NH 32 4.00 2.00 4.00 2.00

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-80_carbon.2.ﬁd 146.798 133.986 131.229 127.050 119.645 110.644 77.160 CDCl3 49.804

NH Br

Br NH 33

160 150 140 130 120 110 100 0102030405060708090 f1 (ppm) rg-01-84_pure3.1.ﬁd 7.331 7.327 7.314 7.309 7.260 CDCl3 7.211 7.194 6.990 6.986 4.671 4.636 4.156 1.189 1.175 1.160

O O

3 OCH O CH3

N Br

Br N 34 2.00 2.00 2.00 2.00 2.02 4.02 6.00

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-86_pure_carbon.1.ﬁd 165.122 146.571 131.396 129.300 128.438 127.311 117.922 83.008 77.160 CDCl3 63.331 56.193 13.969

O O

3 OCH O CH3

N Br

Br N 35

0102030405060708090100110120130140150160170180 f1 (ppm) rg-01-87_pure1.1.ﬁd 7.260 CDCl3 7.231 7.213 7.101 6.970 6.965 6.952 6.947 6.322 4.697 4.662 1.459 1.161 1.146 1.132

O O

3 OCH O CH3

N NH Boc Boc NH N 36 2.00 2.01 2.01 2.00 2.00 2.03 4.00 18.01 6.00 -0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-87_pure1_carbon.1.ﬁd 165.603 152.829 142.775 135.067 127.196 126.051 118.666 115.905 83.491 80.650 77.160 CDCl3 62.999 56.658 28.422 13.980

O O

3 OCH O CH3

N NH Boc Boc NH N 37

0102030405060708090100110120130140150160170180 f1 (ppm) rg-01-89_pure3.5.ﬁd 7.260 CDCl3 7.174 7.157 7.061 7.044 7.020 6.951 6.947 6.934 6.929 6.491 6.487 6.474 6.469 6.412 6.078 6.073 4.636 4.626 4.601 4.591 3.425 1.422 1.105 1.091 1.077

O O

3 OCH O CH3

N NH2

Boc NH N 38 1.00 1.01 1.00 1.01 1.00 1.00 1.02 2.00 2.00 4.00 2.00 9.01 6.00

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-89_carbon1.5.ﬁd 165.642 165.599 152.745 143.268 142.816 138.705 134.836 127.258 126.926 126.315 125.808 118.504 115.897 115.642 111.664 83.417 80.393 77.160 CDCl3 62.759 62.709 56.418 28.270 13.805 13.802

O O

3 OCH O CH3

N NH2

Boc NH N 39

0102030405060708090100110120130140150160170180 f1 (ppm) 7.281 7.263 7.260 CDCl3 7.134 7.117 6.988 6.983 6.971 6.966 6.677 6.659 6.335 4.696 4.661 4.497 4.461 3.839 1.459 1.160 1.155 1.146 1.141 1.132 1.127

O O

3 OCH O CH3 Br N NH2

Boc NH N 40 1.00 2.00 1.00 1.00 1.00 1.00 1.01 2.00 4.01 2.00 9.02 6.00 -0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) 165.49 152.85 142.88 141.33 139.75 135.16 127.23 126.75 126.24 125.41 118.79 115.98 115.41 108.32 83.28 80.69 77.16 CDCl3 63.05 58.26 56.60 28.41 13.98 13.96

O O

3 OCH O CH3 Br N NH2

Boc NH N 41

-100102030405060708090100110120130140150160170180190200210 f1 (ppm) rg-01-104_pure1.1.ﬁd 7.974 7.955 7.722 7.703 7.375 7.357 7.260 CDCl3 7.169 6.922 6.918 6.905 6.900 6.286 5.050 5.012 4.978 4.941 4.774 4.738 4.454 4.419 1.415 1.206 1.192 1.178 1.106 1.092 1.078

OO Et Et O O

OO Et Et N NH O O Boc

42 N N N

Boc NH N (-) 2.00 2.00 2.01 2.00 2.01 2.00 4.00 2.00 2.00 8.00 18.01 6.00 6.00 -0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-104_pure1_carbon.1.ﬁd 165.427 165.290 152.762 147.988 142.806 140.914 135.183 129.893 129.229 126.526 126.452 123.304 118.752 115.892 83.648 80.638 77.160 CDCl3 63.193 63.164 54.926 54.041 28.370 14.011 13.981

OO Et Et O O

OO Et Et N NH O O Boc

43 N N N

Boc NH N (-)

0102030405060708090100110120130140150160170180 f1 (ppm) rg-01-105_pure1a.1.ﬁd 7.975 7.970 7.957 7.951 7.731 7.720 7.713 7.701 7.379 7.361 7.270 7.260 CDCl3 7.253 7.173 6.927 6.922 6.910 6.905 6.539 6.534 6.522 6.517 6.280 6.153 6.148 5.056 5.045 5.019 5.008 4.977 4.948 4.940 4.911 4.780 4.751 4.745 4.717 4.459 4.423 3.427 1.423 1.210 1.195 1.184 1.182 1.170 1.105 1.097 1.091 1.083 1.076 1.069

OO Et Et O O

OO N Et Et NH2 O O

44 N N N

Boc NH N (-) 2.00 2.00 1.00 1.01 1.01 1.00 1.00 1.01 1.00 5.00 2.00 1.00 8.01 2.00 9.02 6.00 6.00

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-105_pure1_carbon.1.ﬁd 165.607 165.419 165.409 165.272 152.755 148.166 147.913 143.536 142.782 140.994 140.875 140.832 138.950 135.163 129.970 129.809 129.226 129.049 126.958 126.500 126.433 126.396 123.567 123.238 118.749 115.887 111.735 83.768 83.624 80.612 77.160 CDCl3 63.168 63.132 63.064 63.056 54.891 54.817 54.025 53.929 28.356 13.988 13.954

OO Et Et O O

OO N Et Et NH2 O O

45 N N N

Boc NH N (-)

0102030405060708090100110120130140150160170180 f1 (ppm) rg-01-107_pure4.1.ﬁd 8.012 7.995 7.978 7.764 7.747 7.729 7.626 7.391 7.373 7.260 CDCl3 7.200 6.936 6.914 6.327 4.784 4.749 1.421 1.239 1.225 1.212 1.199 1.184 1.122 1.115 1.108 1.101 1.094 1.087

OO Et Et O O

OO Br N Et Et NH2 O O

N N 46 N N

Boc NH N (-) 2.01 2.00 1.00 1.01 1.01 1.00 1.01 4.01 1.01 3.00 8.02 9.01 6.02 6.01

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-107_pure4_carbon.1.ﬁd 165.389 165.268 165.152 164.873 152.814 148.094 147.781 142.765 141.040 140.954 140.924 140.757 139.756 139.568 135.174 130.067 129.771 129.535 129.222 128.971 126.530 126.467 125.853 123.302 123.105 115.951 108.216 107.726 83.619 83.283 80.736 77.160 CDCl3 63.441 63.371 63.254 63.224 56.532 54.910 54.240 54.030 28.369 14.032 13.999

OO Et Et O O

OO Br N Et Et NH2 O O

N N 47 N N

Boc NH N (-)

0102030405060708090100110120130140150160170180 f1 (ppm) rg-01-30_distilled_pure.1.ﬁd 7.260 CDCl3 4.355 0.132

3CH O O CH3 Si Si 3CH CH3 CH3 CH3 48 4.00 18.00 -0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-30_distilled_pure_carbon.1.ﬁd 208.571 77.160 CDCl3 67.194 -0.497

3CH O O CH3 Si Si 3CH CH3 CH3 CH3 49

-100102030405060708090100110120130140150160170180190200210 f1 (ppm) rg-01-31_pure.1.ﬁd 7.260 CDCl3 5.090 5.087 5.085 4.132 4.130 4.128 0.124

CH2

3CH O O CH3 Si Si 3CH CH3 CH3 CH3 50 2.00 4.00 18.02 -0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-31_pure_carbon.1.ﬁd 147.625 110.214 77.160 CDCl3 63.484 -0.335

CH2

3CH O O CH3 Si Si 3CH CH3 CH3 CH3 51

-100102030405060708090100110120130140150160170180190200210 f1 (ppm) rg-01-33_pure.1.ﬁd 7.160 C6D6 4.544 4.527 4.383 4.356 4.152 4.125 4.081 4.054 3.998 3.971 2.785 2.781 2.771 2.767 2.757 2.753 2.743 2.739 2.729 2.725 2.537 2.533 2.530 2.526 2.510 2.506 2.503 2.499 1.147 1.133 1.057 1.043 0.856 0.843 0.821 0.812 0.796 0.788 0.773 0.747 0.721

CH3

3CH OO CH3

52 2 2.01 1.00 1.01 1.01 1.00 0.98 1.00 4.02 1.03 3.03 3.03 3.05 1.00 1.03

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-33_pure_carbon.1.ﬁd 141.310 128.060 C6D6 107.839 100.513 63.771 63.445 51.727 38.262 35.346 29.490 24.948 24.191 22.825 22.459 19.414

CH3

3CH OO CH3

53 2

150 140 130 120 110 100 0102030405060708090 f1 (ppm) rg-01-71_very_pure.2.ﬁd 7.260 CDCl3 4.345 4.284 4.247 4.220 4.183 2.409 2.406 2.395 2.392 2.381 2.378 2.367 2.364 2.354 2.350 2.340 2.337 2.326 2.323 2.234 2.230 2.227 2.223 2.206 2.202 2.199 2.195 1.773 1.747 1.030 1.003 0.977 0.940 0.925 0.923 0.916 0.910 0.902 0.880 0.873 0.848 0.835

CH3

3CH OO CH3

54 O 2.00 1.00 1.02 1.01 1.00 1.02 2.03 2.00 1.01 3.02 3.03 3.01 1.00

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-71_very_pure_carbon.1.ﬁd 207.459 101.555 77.160 CDCl3 68.741 67.980 51.418 40.330 34.733 29.748 24.663 23.833 22.531 22.174 18.736

CH3

3CH OO CH3

55 O

0102030405060708090100110120130140150160170180190200210 f1 (ppm) rg-01-74_bottom_diast.1.ﬁd 7.313 7.308 7.295 7.291 7.279 7.274 7.260 CDCl3 7.260 7.258 7.076 7.059 7.020 7.016 6.985 6.981 6.936 6.919 4.728 4.693 4.385 4.350 4.142 4.107 4.076 4.053 3.979 3.944 3.879 3.872 3.853 3.846 3.815 3.808 3.793 3.785 3.684 3.658 2.706 2.681 2.602 2.598 2.588 2.584 2.574 2.571 2.560 2.557 2.546 2.543 1.726 1.701 1.031 1.017 0.939 0.925 0.885 0.871 0.852 0.844 0.814 0.724 0.698 0.672

CH3

3CH

CH3OO

56 Br N

N Br (+) 2.03 1.01 1.01 1.01 1.01 1.02 1.01 1.02 1.02 1.03 1.01 1.04 1.01 1.00 1.00 1.02 1.03 2.02 1.01 3.01 3.00 3.03 1.00 1.02

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-74_bottom_diast_carbon.1.ﬁd 146.780 146.506 131.257 131.067 130.353 129.543 129.274 129.045 128.725 127.757 117.336 116.844 100.768 77.160 CDCl3 66.555 63.227 63.080 54.337 54.054 50.981 36.556 35.024 29.372 24.824 23.858 22.421 22.306 19.270

CH3

3CH

CH3OO

57 Br N

N Br (+)

170 160 150 140 130 120 110 0102030405060708090100 f1 (ppm) rg-01-74_top1_diast.1.ﬁd 7.302 7.298 7.286 7.281 7.269 7.264 7.260 CDCl3 7.058 7.041 7.027 7.022 6.977 6.973 6.939 6.922 4.757 4.722 4.373 4.338 4.154 4.119 3.978 3.943 3.893 3.870 3.853 3.808 3.805 3.786 3.782 2.703 2.701 2.677 2.674 2.624 2.621 2.610 2.607 2.597 2.593 1.723 1.699 0.973 0.970 0.959 0.956 0.906 0.893 0.877 0.870 0.852 0.845 0.712 0.686 0.660

CH3

3CH

CH3OO

58 Br N

N Br (-) 2.01 1.01 1.00 1.00 1.01 1.00 1.00 1.01 1.01 3.02 1.00 1.00 1.01 1.01 2.00 1.02 1.00 3.02 3.01 3.01 1.00 1.01

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-74_top1_diast_carbon.1.ﬁd 146.765 146.495 131.261 131.096 130.341 129.510 129.375 129.007 128.638 127.782 117.379 116.838 100.596 77.160 CDCl3 66.507 63.267 62.909 54.305 54.175 51.071 36.508 35.037 29.527 24.873 23.784 22.372 22.103 18.956

CH3

3CH

CH3OO

59 Br N

N Br (-)

170 160 150 140 130 120 110 0102030405060708090100 f1 (ppm) rg-01-78_extra_pure.1.ﬁd 7.308 7.304 7.291 7.287 7.260 7.260 CDCl3 7.040 7.026 7.022 4.587 4.552 4.066 4.031 3.917 3.894 3.844 3.820 2.698

OH OH

Br N

Br 60 N

(+) and (-) 2.00 4.01 2.02 2.01 2.01 2.01 2.00

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0 f1 (ppm) rg-01-78_extra_pure_carbon.1.ﬁd 146.446 131.295 130.187 129.443 128.001 117.581 77.160 CDCl3 73.775 63.613 54.804

OH OH

Br N

Br 61 N

(+) and (-)

160 150 140 130 120 110 100 0102030405060708090 f1 (ppm) rg-01-104_pure1.1.ﬁd 7 . 9 4 7 . 9 5 7 . 2 7 . 0 3 7 . 3 5 7 . 3 5 7 . 2 6 0 C D l 3 7 . 1 6 9 6 . 9 2 6 . 9 1 8 6 . 9 0 5 6 . 9 0 6 . 2 8 5 . 0 5 . 0 1 2 4 . 9 7 8 4 . 9 1 4 . 7 4 . 7 3 8 4 . 5 4 . 1 9 1 . 4 5 1 . 2 0 6 1 . 9 2 1 . 7 8 1 . 0 6 1 . 0 9 2 1 . 0 7 8

O O HC HD HA HB

HE HF O O HE HF HE HF O O HA HB HC HD H H F E 5 . 0 5 . 0 1 2 4 . 9 7 8 4 . 9 1 4 . 7 4 . 7 3 8 4 . 5 4 . 1 9 O O H HF HE HF HE N H H HN HK I HO HM N H HN N J H HL N O N H HH, HG E HN O H HG N H , H 62 HQ N N HP HN HN HJ, HI B C H H HF N N HH N HN HN HP N HG HH HQ HN O HN HD HN O N N HL HA HN H HM HO H HJ HK HN N I 4 . 0 2 . 0 2 . 0 8 . 0 5.2 5.1 5.0 4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 H f1 (ppm) HQ K H L H HO H M P 2 . 0 2 . 0 2 . 0 1 2 . 0 2 . 0 1 2 . 0 4 . 0 2 . 0 2 . 0 8 . 0 1 8 . 0 6 . 0 6 . 0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 f1 (ppm)

rg-01-104_pure1_carbon.1.ﬁd 1 6 5 . 4 2 7 1 6 5 . 2 9 0 1 5 2 . 7 6 1 4 7 . 9 8 1 4 2 . 8 0 6 1 4 0 . 9 1 3 5 . 8 1 2 9 . 8 3 1 2 9 . 1 2 6 . 5 1 2 6 . 4 5 1 2 3 . 0 4 1 8 . 7 5 2 1 5 . 8 9 2 8 3 . 6 4 8 0 . 6 3 7 . 1 6 0 C D l 3 6 3 . 1 9 6 3 . 1 4 5 4 . 9 2 6 5 4 . 0 1 2 8 . 3 7 0 1 4 . 0 1 3 . 9 8

O O

C2 C20 C20 C2 C1 O C7 O C1 C5 O O

C2 C20 C20 C2 C O C O C C 1 7 1 N C H 5 C16 4 C8 N O C5 C17 C15 C13 C9 C19 C6

C18 C14 C12 C10 O C5 N C C 18 C3 N 11 N C C11 3 C18 N 63 C5 O C10 C12 C14 C18 C5 C6 C19 C9 C13 C15 C17 C5 O N C8 C16 H C4 N C1

C18 C7 C2 C20 C9 C11, C13 C19 C12 C14

C15 C16 C6 C8 C4 C3 C10 C17

160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 f1 (ppm)

HPLC Chromatographs Chiral AD-H resolution of mono-Boc TB monomer 18

Column- Chiral AD-H analytical Mobile Phase- 60:40:0.1 Hexanes/Isopropanol/Diethyl amine Flow rate- 1 mL/min Loading- 20 µL (1 mg/mL solution)

Chiral AD-H analytical resolution of racemic TB 18

(-)-enantiomer of TB 18

(+)-enantiomer of TB 18

Column- Chiral AD-H semiprep Mobile Phase- 60:40:0.1 Hexanes/Isopropanol/Diethyl amine Flow rate- 15 mL/min Loading- 400 µL (100 mg/mL solution)

Chiral AD-H semiprep resolution of racemic TB 18

DynaFit Script

Preliminary binding studies between bis-Boc dimer 20 and hydroquinone

[task]

data = equilibria task = fit

[mechanism]

H + G <==> H.G : Ka assoc

[constants]

Ka = 0.1 ?

[responses]

intensive

[settings]

{Output} BlackBackground = n

[data] variable G, H plot titration graph host.a set 1H.host.a | resp H = 7.92355 ? , H.G = 7.92505 ? graph host.b set 1H.host.b | resp H = 7.7472 ? , H.G = 7.7481 ? graph host.c set 1H.host.c | resp H = 7.14895 ? , H.G = 7.1493 ?

graph host.d set 1H.host.d | resp H = 7.059925 ? , H.G = 7.0595 ? graph guest.a set 1H.guest.a | resp G = 6.52914 ? , H.G = 6.53021 ?

[set:1H.host.a] G, mM H, mM ppm 0.000 3.377 7.92355 3.846 3.117 7.92410 7.143 2.895 7.92455 10.00 2.702 7.92495 12.50 2.533 7.92505

[set:1H.host.b] G, mM H, mM ppm 0.000 3.377 7.747200 3.846 3.117 7.747550 7.143 2.895 7.747800 10.00 2.702 7.747975 12.50 2.533 7.748100

[set:1H.host.c] G, mM H, mM ppm 0.000 3.377 7.14895 3.846 3.117 7.1491 7.143 2.895 7.1492 10.00 2.702 7.14925 12.50 2.533 7.1493

[set:1H.host.d] G, mM H, mM ppm 0.000 3.377 7.059925 3.846 3.117 7.059800 7.143 2.895 7.059650 10.00 2.702 7.059575 12.50 2.533 7.059500

[set:1H.guest.a] G, mM H, mM ppm 3.846 3.117 6.52914 7.143 2.895 6.52960 10.00 2.702 6.53000 12.50 2.533 6.53021

[end]