Synthesis and properties of methyl 5-(1R,2S)-(2-octadecylcycloprop-1-yl)pentanoate and other ω-19 chiral cyclopropane fatty acids and esters related to mycobacterial mycolic acids

Coxon, G.D. and Al Dulayymi, J.R. and Morehouse, C. and Brennan, P.J. and Besra, G.S. and Baird, M.S. and Minnikin, D.E. (2004) Synthesis and properties of methyl 5-(1R,2S)-(2-octadecylcycloprop-1-yl)pentanoate and other ω-19 chiral cyclopropane fatty acids and esters related to mycobacterial mycolic acids. Chemistry and Physics of Lipids, 127 (1). pp. 35-46. ISSN 0009-3084

Abstract

A 23–26-carbon chain length range of ω-19 (1′R,2′S) cyclopropane fatty acids, related to mycobacterial mycolic acids, has been prepared. The key cyclopropyl intermediate, (1′R,2′S)-(Z)-1-formyl-2-octadecylcyclopropane, underwent Wittig chemistry with various reagents to provide vinylic precursors, which were selectively reduced to the corresponding saturated ω-19 cyclopropane fatty acids or esters. The 24-carbon ω-19 cyclopropane ester was made by chain elongation of the 23-carbon ester. Saturated and unsaturated chiral cyclopropane acids and esters were assayed, using wall extracts of Mycobacterium smegmatis; the incorporation of -acetate was used to measure inhibition or stimulation of mycolic acid synthesis. Minor inhibition (2–3%) was shown by the 23- and 24-carbon saturated esters; all the other compounds were stimulants. The most effective (38–55%) stimulators of mycolate synthesis were the unsaturated esters with 23- and 26-carbons and the saturated and unsaturated 25-carbon acids.

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