Synthesis of 1α, 5α-cyclosteroids

Ren, Yi (1992) Synthesis of 1α, 5α-cyclosteroids. Masters thesis, Memorial University of Newfoundland.

[img] [English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version
Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.

Download (11MB)
  • [img] [English] PDF - Accepted Version
    Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
    (Original Version)

Abstract

Epoxidation of 4,4-dimethylcholesta-1,5-dien-3-one with m-chloroperbenzoic acid gave a mixture of the epimeric 5α, 6α-epoxy- and 5β, 6β-epoxy-4,4-dimethylcholest-1-en-3-one. Unexpectedly, the major product was found to be the 5β, 6β-epoxide, in contradiction to what had been reported by others. The unambiguous assignment of the structures of these epoxides was based upon ¹H NMR experiments and X-ray crystallographic analysis of the 5α, 6α-epoxide. In this thesis, the chemistry of the 5β, 6β-epoxide is described in the context of attempts at the synthesis of the corresponding 1α, 5α-cyclosteroids. -- The synthesis of a new 1α, 5α-cyclosteroid, 4, 4-dimethyl- 1α, 5α-cyclocholesta-3,7-dione, by lithium or ytterbium in liquid ammonia reduction of the bis-α, β-unsaturated ketone 4, 4-dimethylcholesta-1,5-diene-3,7-dione, is described. The chemistry of the reductive cyclization is discussed. The ¹H- NMR spectra of the mono- and dihydroxy derivatives of the 1α, 5α-cyclosteroid reveal an unusually high-field signal due to H-9. X-ray diffraction analysis of 7β-hydroxy-4, 4-dimethyl- 1α, 5α-cyclocholestan-3-one indicates that ring B of the steroid nucleus possesses a boat conformation, and that H-9 partially eclipses the cyclopropyl ring. An anisotropic ring current effect is postulated to account for the chemical shifts of H-9 in these cyclosteroids. The chemistry of these compounds are described. -- Various other attempts at the synthesis of 1a, 5a- cyclosteroids are also described.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/4256
Item ID: 4256
Additional Information: Bibliography: leaves 97-101. -- Alpha appears on t.p. as the Greek character.
Department(s): Science, Faculty of > Chemistry
Date: 1992
Date Type: Submission
Library of Congress Subject Heading: Steroids--Synthesis

Actions (login required)

View Item View Item

Downloads

Downloads per month over the past year

View more statistics