Synthesis of (24R)- and (24S)-5,28-Stigmastadien-3β-ol and Determination of the Stereochemistry of Their 24-Hydroxy Analogues, the Saringosterols

Article abstract of DOI:10.1021/jo00174a011

Both epimers at C-24 of 5,28-stigmastadien-3β-ol (24-vinylcholesterol) were synthesized from 5,24(28)-ergostadien-3β-ol, and their configuration at C-24 was determined by conversion into clionasterol and sitosterol. 24-Vinylcholesterol has not yet been found in nature, but it is a possible intermediate in the biosynthesis of 24-propylcholesterol and 24-propylidenecholesterol.A structurally related compound, 5,28-stigmastadiene-3β,24ξ-diol (saringosterol), first isolated from a brown seaweed, was shown to be a mixture of epimers at C-24.They were seperated and their configuration was determined by correlation with fucosterol and isofucosterol 24(28)-epoxides of known stereochemistry.