Conversion of Steroidal Vicinal Diols to the Corresponding Olefinic Compounds

The wide applicability of two-step conversion of a vicinal diol group to carbon-carbon double bond developed by Corey and Winter was examined for various steroids with vicinal diol (s). By refluxing with triethyl phosphite, cyclic thionocarbonates derived from the vicinal diol steroids were converted to the corresponding olefinic steroids in high yields. Using this two-step conversion as a key step, brassinosteroid-related compounds, (22R, 23R, 24S) - and (22S, 23S, 24S) -2α, 3α, 22, 23-diepoxy-B-homo-7-oxa-5α-stigmastan-6-ones produced more efficiently than reported to date.