A synthetic study of some triquinane natural products and microbial reduction of prochiral spirodiketones

Zhu, Yanyi (1993) A synthetic study of some triquinane natural products and microbial reduction of prochiral spirodiketones. 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 (14Mb)
  • [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

The first half of this thesis describes an approach to the synthesis of a group of triquinane sesquiterpenes, with (±) deoxypentalenic acid as the particular target. The synthesis started from readily available isophorone. The central quaternary center of the natural product was established in an early step by a double acylation reaction on a cyclohexene derivative. Cleavage of the double bond was followed by reclosure to a five-membered ring. The relative stereochemistry at a stereogenic methine was controlled by catalytic hydrogenation. An intramolecular aldol reaction was used to cyclize the third ring of the triquinane moiety. The remaining steps to (±)-deoxypentalenic acid were modeled in reactions leading to β-keto esters and in reductions of the ketone moiety of a β-keto ester. -- The second part of the thesis provides the results of chiral reductions of 1,3-cyclopentanedione derivatives using baker's yeast. The series of diketones that was examined included 7,9,9-trimethylspiro[4.5|dec-7-ene-1,4-dione. The yeast reduction of this compound to (4S,5R)-4-hydroxy-7,9,9-trimethylspiro[4.5]dec-7-en-l-one (123) proceeded with high facial selectivity and enantioselectivity, as determined by an analysis of the corresponding Mosher's ester [(+)-α-methoxy-α-trifluoromethylphenyl-acetate derivative]. The facial selectivity was compared with that of the chemical reduction using sodium borohydride. The absolute stereochemistry was established from CD spectra and an X-ray structure. The transformation of compound 123 into (4R,5S)-4-hydroxy-4,7,9,9-tetramethylspiro[4.5]dec-7-en-l-one, an optically active form of an intermediate in the triquinane synthesis, required four steps.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/4247
Item ID: 4247
Additional Information: Bibliography: leaves 110-116.
Department(s): Science, Faculty of > Chemistry
Date: 1993
Date Type: Submission
Library of Congress Subject Heading: Quinanes; Ketones; Sesquiterpenes

Actions (login required)

View Item View Item

Downloads

Downloads per month over the past year

View more statistics