Synthesis of polyhydroxysterols (III): synthesis and structural elucidation of 24-methylenecholest-4-en-3β,6α-diol

Abstract

Using stigmasterol as the starting material, 24-methylenecholest-4-en-3β,6α-diol ( 2) was synthesized in eight steps in 13% overall yield. The introduction of the sterol side-chain was carried out using (3-methyl-2-oxobutyl)-triphenylarsonium bromide ( 11) and K 2CO 3 in a solid–liquid phase-transfer Wittig reaction. Construction of the steroidal nucleus was finished by oxidation of 24-methylenecholest-5-en-3β-ol ( 9) with pyridinium chlorochromate (PCC) in dichloromethane at ambient temperature and by reduction of 24-methylenecholest-4-en-3,6-dione ( 10) with NaBH 4 in the presence of CeCl 3·7H 2O.