Steroid conjugates. Part IV. The influence of the cation in borohydride reduction of ketol sulphates

Abstract

Acetal formation is preferred to reduction when pyridinium salts of 3-keto-steroid sulphates are treated with sodium borohydride in anhydrous methanol, whereas alkali-metal salts are reduced in the normal way. This difference is explained by the acidity of the pyridinium ion, which is sufficient to promote acetalisation of unhindered ketones. Significant variations occur in the ratio of the epimeric alcohols formed in the presence of added cations.