Bufadienolides. 4. Reaction of 20-Oxo Steroids with Methoxymethylenetriphenylphosphorane

Reaction of 20-oxo-5-pregnenes 1a-1c with the ylide prepared from methoxymethyltriphenylphosphonium chloride was studied in. detail. Vinyl ether 2a was also obtained along with a comparable amount of 3β-acetoxy-26,27-bisnor-5,20 (22)cholestadiene (3a), employing the mixture of phosphoranes from methoxymethyltri-n-butylphosphonium chloride. Acid-catalyzed hydrolysis of vinyl ether 2 afforded aldehyde 4. Attempts to condense methoxymethylenetriphenylphosphorane with trans olefinic ketone Sa, cis olefinic ketone 6a, or saturated ketone 7a led to extensive side reactions attributable to the methyl ester group. Use of the carboxylic acid (7b) or the t-butyl ester (7b) or amide (7d) eliminated side reactions but satisfactory involvement of the 20 ketone was not realized.