Abstract
Several 7-ketones of lanostane, 4, 4-dimethylcholestane and cholestane derivatives were subjected to catalytic hydrogenation on platinum, reduction with complex hydrides and reduction with sodium in tert-butanol, and the product ratios (7α-ol/7β-ol) were determined by gas chromatography or high-performance liquid chromatography. Catalytic hydrogenation of 3β-hydroxylanostan-7-one and3β-hydroxy-4, 4-dimethylcholestan-7-one yielded the 7β-alcohols as the major products, whereas their 3-acetates gave principally the7a-alcohols. Reduction of various 7-ketones with sodium in tert-butanol gave mainly the 7βequatorial alcohols, while the epimeric7α-ols were the major products on reduction with lithium tri-sect-butylborohydride. The stereoselectivity of reduction with sodium borohydride and lithium aluminum hydride was highly dependent on the neighboring double bond and 4, 4-dimethyl and/or 14α-methyl substituent (s).
