Synthesis of 24-methyl-26-hydroxysteroid side-chains: models for stereochemical assignments in polyhydroxylated marine steroids

Abstract

Stereoisomers of Δ^22E and saturated 24-methyl-26-hydroxy steroids have been synthesized via a Claisen rearrangement as model compounds of established absolute configuration for stereochemical assignments at C-24 and C-25 of marine 24-methyl-26-hydroxy steroids. Analysis of NMR spectral data of synthetic compounds and of their MTPA esters proved the suitability of NMR spectroscopy for the assignment of configurations at C-24 and C-25 of unknown 24-methyl-26-hydroxy steroids. The absolute configurations at C-24 and C-25 of two naturally occurring marine steroids from a starfish and an ophiuroid have been established.