43 イノコステロンの立体構造,合成および分離

概要

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Inokosterone, a phytoecdysone isolated from Achyranthes fauriei (Amaranthaceae), has been partially acetylated to give the 2,26-diacetate (2) which has been converted into methyl 5-acetoxy-4-methylpentanoate (9) and 2β-acetoxy-3β,14α-dihydroxy-5β-pregn-7-ene-6,20-dione (3). Chemical and physico-chemical studies have shown the configurations at C-20 and C-22 to be R. Inokosterone has thus been concluded to be a mixture of C-25 epimers of (20R,-22R)-2β,3β,14α,20,22,26-hexahydroxy-5β-cholest-7-en-6-one (1). After the synthesis of the model compound, a C-25 epimeric mixture of (20R,22R)-3β,20,22,26-tetrahydroxy-5α-cholestane (16), inokosterone has been synthesized via (20R)-2β,3β,14α,20-tetrahydroxy-20-formyl-5β-pregn-7-en-6-one (18) by Grignard reaction with 4-(tetrahydropyran-2-yloxy)-3-methylbutynylmagnesium bromide (12) followed by hydrogenation and hydrolysis. The use of an NMR shift reagent with the inokosterone acetates (4, 21) and the optical activity measurement of α-methylglutaric acid (6) derived from inokosterone have established that inokosterone is a 1: 2 mixture of the C-25 R and S epimers. Inokosterone was then submitted to high speed liquid chromatography using a Permaphase ODS column to separate the two epimers, inokosterone A and B, which were very similar in the physico-chemical and biological properties to each other. The proportion of both epimers was found to vary depending upon the plant materials.
1976-09-20