The two C 8 epimers of 3β-Acetoxylanost-9(11)-en-7-one

Abstract

Chromium trioxide-acetic acid oxidation of 3β-acetoxylanost-8-ene (1) at approximately 50� yields 3β-acetoxylanosta-7,9(11)-diene (2), 3β- acetoxylanost-8-ene-7,11-dione (3), 3β-acetoxylanost-8-en-7-one (4), and 3β-acetoxy-8β-lanost-9(11)-en-7-one (5). The α,β-unsaturated ketone (4) is not an intermediate in the formation of (3), the oxidation sequence being (1) → (2) → (5) → (3). ��� Mild 30% hydrogen peroxide-acetic acid oxidation of (1) at 20� affords (2) in almost quantitative yield while further reaction under the same conditions gives 3β-acetoxy-8α-lanost-9(11)-en-7-one (6).