Structure elucidation of (22E,24R,25R)-24-methyl-5α-cholest-22-ene-3β,4β,5,6α,8,14,15α,25,26-nonaol and (22E,24S)-24-methyl–5α-cholest-22-ene-3β,4β,5,6α,8,14,15α,25,28-nonaol, minor marine polyhydroxysteroids isolated from the starfish Archaster typicus

Abstract

The structures of two minor polyhydroxysteroids isolated from the starfish Archaster typicus were determined as (22E,24R,25R)-24-methyl-5α-cholest-22-ene-3β,4β,5,6α,8,14,15α,25,26-nonaol (4) and (22E,24S)-24-methyl-5α-cholest-22-ene-3β,4β,5,6α,8,14,15α,25,28-nonaol (5).

The stereochemistry at the C-24 and C-25 positions in compound (4) was determined by asymmetric synthesis of 2,3-dimethylpentane-1,2-diols as models and comparison of the spectral data of their 1(+)-MTPA esters with those of the 26-(+)-MTPA ester of the 22,23-dihydro derivative of the natural material. Similarly the stereochemistry at the C-24 position in compound (5) was proposed by comparison of the spectral data with those of a model compound.