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Information to Users INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the orignal or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be fi-om any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zeeb Road, Ann Artor MI 48106-1346 USA 313/761-4700 800/521-0600 AN APPROACH TO STRYCHNOS ALKALOIDS VIA INTRAMOLECULAR 1,3-DIPOLAR CYCLOADDITION DISSERTATION Presented in Partial Fuifillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University By Ving Huang, M.S. The Ohio State University 1 9 9 8 Dissertation Committee: ApprovedApproved by by Dr. David J. Hart, Adviser Dr. Gideon A. Frankei Dr. Jon Parquette Adviser Department of Chemistry UMI Number: 9900846 UMI Microform 9900846 Copyright 1998, by UMI Company. All rights reserved. This microform edition Is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, Ml 48103 ABSTRACT This thesis examines an approach to the Strychnos alkaloids via an intramolecular 1,3- dipolar cycloaddition. The first chapter presents an overview of prior approaches to Strychnos alkaloids to place this work in context. The next chapter describes the development of a general method for the preparation of /V-trialkylsilylmethyl-2-cyano-1,2,3,6-tetrahydropyridines via reductive cyanation of /y-trialkyl- silylmethyl pyridinium salts. /V-Alkylation of substituted pyridines with (fe/t-butyldiphenyl- silyl)methanyl trifluoromethanesulfonate gave A/-[{ferf-butyldiphenylsilyl)methyl]pyridinium triflates. Reduction of these salts with NaBH« in the presence of NaCN gave the target tetrahydropyridines. Problems associated with the use of trimethylsilylmethyl iodides in this sequence are discussed. It was demonstrated that by carefully selecting ncn-nucleophiiic counterions (triflate instead of iodide) and indroducing steric hindrance at silicon (TBDPS instead of IM S), it is possible to retain silicon through the reaction sequence. It was demonstrated that N- trialkylsilylmethyl-2-cyano-1,2,3,6-tetrahydropyridines gave azomethine ylids upon treatment with AgF, and the azomethine ylid would undergo intermolecular cycloaddition to very reactive dipolarophiles, such as AAmethylmaleimide and frarjs-1,2-bis(phenylsulfonyl)ethylene. Intramolecular versions of this reductive cyanation-cycloaddition sequence were then investigated within the context of the aforementioned approach to Strychnos alkaloids. N-[[tert- Butyldiphenylsilyl)methyl]-5-[(2)-ethylidene]-4-(2-oxo-3-phenyl-3-butenyl)-2-pjperidinecarbo- nit rile was prepared in six steps and 10% overall yield from a-methyl-3-pyridinemethanol. Upon treatment with AgF, this ylid precursor gave no cycloaddition product, but instead gave a perhydroisoquinoline. Formation of this product was attributed to generation of an enamine from the azomethine ylid, followed by an intramolecular Michael addition to the a,p-unsaturated ketone. It was proposed that trapping of the azomethine ylid was inefficient due to an unfavorable conformational equilibrium. Several studies directed toward the synthesis of /V-[(rert-butyldiphenylsilyl)methyl]-5-[(£)- ethylidene]-4-(2-oxo-3-phenyl-3-butenyl)-2-piperidinecarbonitrile were conducted, with the hope that A’’^-strain would overcome the aformentioned conformational problem. N-[(tert- Butyldiphenylsilyl)methyl]-5-[(£)-ethylidene]-4-(2-hydroxy-3-phenyl-3-butenyl)-2-piperidine- carbonitrile was prepared in 6 steps and 9% yield from 5,6-dihydro-2H-pyran-2-one using a cuprate conjugate addition in the key step. The oxidation of 1-[(ferr-butyldiphenylsilyl)methyl]-5- [(£)-ethylidene]-4-(2-hydroxy-3-phenyl-3-butenyl)-2-piperidinecarbonitrile to /V-[(ferr-butyl- diphenylsilyl)methyl]-5-[(£)-ethylidene]-4-(2-oxo-3-phenyl-3-butenyl)-2-piperidinecarbonitrile, however, could not be accomplished. Alternative approaches to N-[trialkylsilylmethyl]-5-[(E)- ethylidene]-4-(2-oxo-3-phenyl-3-butenyl)-2-thiopiperidone are proposed. lU To Rachel and Chen IV ACKNOWLEDGMENTS I am very fortunate to have Dr. Hart as my advisor. It is with him I started to be a chemist, although not a good one. I appreciate the opportunities of being showed how things are supposed to be done by the master, which I probably have to spend my whole life to strive for. I am also fortunate to know him as a human being during my toughest struggles through the program. It is always comforting to know somebody really cares. I hope that I am a better chemist and a more mature person now, and I owe that to Dr. Hart. The only regret is that I wish I actually listened to him more. I certainly hope I will be a better chemist and a better person in the years to come, because I always know I have his reputation at stake. Past and current members of the Hart group are deeply appreciated. Brian helped me a lot when I first started here. My current labmate Jane is appreciated for being such a good girlfriend to hear me out so many times, although I am so sorry to be “emotionally high- mantainace”. Also, Scott was always there when a helping hand is needed. Jim and Mike will be remembered for the interesting talks. I would also like to thank Chen, my husband, for his love and confidence in me which helped me endure my stay here in Columbus. I am also indebted to my mom and dad for helping me take care of my little daughter, Rachel, when Chen had to be away on his job. All the love and support from my parents were taken for granted for so long. And Rachel, as little as she is, is so amazingly supportive. Not a day goes by that I was not reminded of the miracle I have in front of me, in my little girl’s eyes. The Highpiont Chinese Church is also greatly appreciated for providing me a home away from home and their prayers are well felt. V VITA October 21, 1965 ......................................................................Born, Shanghai, China 1984-1988................................................................................... 8 . S., Fudan Universitery, China. 1988-1990................................................................................... Research Assistant, Shanghai Institute of Organic Chemistry. 1992..............................................................................................M. S., West Virginia University, Morgantown, WV. 1992-1994................................................................................... Teaching Assistant, The Ohio State University, Columbus, Ohio. 1995-1998................................................................................... Reserach Assistant The Ohio State University, Columbus, Ohio. PUBLICATIONS Andemicheal, Y. W.; Huang, Y.; Wang, K. K Thermally Induced One-Step Construction of the Tetracyclic Steroidal Skeleton from Acyclic Enyne-allene”, J. Org. Chem. 1993, 58, 1651. Huang, Y.; Hart, D. J. “A 1,3-Dipolar Cycloaddition Approach towards Total Synthesis of Strychnos Alkaloids", 29th Central Regional Meeting of the American Chemical Society, Midland, Ml, May, 1997. Fields of Study Major Field: Chemistry VI TABLE OF CONTENTS ABSTRACT...................................................................................... :...................................... ii DEDICATION.......................................................................................................................... iv ACKNOWLEDGMENTS..........................................................................................................v VITA.......................................................................................................................................... Vi TABLE OF CONTENTS....................................................................................................... vii LIST OF FIGURES...................................................................................................................ix LIST OF SCHEMES.............................................................................................................. x LIST OF TABLES................................................................................................................ xiii CHAPTER PAGE 1. ISOLATION, STRUCTURE ELUCIDATION, BIOLOGICAL ACTIVITY AND SYNTHESIS OF SELECTED STflYCH/VOS ALKALOIDS.............. 1 I. Introduction................................................................................1 II. Occurrence and
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