A refined method for determining the absolute configuration of the 3-hydroxy-3-methylglutaryl group

A refined method for the determination of the absolute configuration of the 3-hydroxy-3-methylglutaryl group in natural products was developed. An interchange between the order of reduction with lithium borohydride and amidation with a chiral amine described in the previous procedure resulted in a high yield of the desired derivative. The refined method is applicable to various natural products with the 3-hydroxy-3-methylglutaryl group, even if their available amounts are 0.1 mg. The absolute configuration of the group in the lanostane-type triterpene acid, which had been isolated in a small amount, was established as S.

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(3R)-5-O-Acetyl-1-[(S)-phenylethyl]mevalonamideC16H23NO4Ee = 100%[α]D18=-59.0 (c 3.75, CHCl3)Source of chirality: natural productAbsolute configuration: (3R)