| 摘要 |
NEW MATERIAL:A compound of formula I (R is H, silyl, trityl, t-butyl, benzyl). EXAMPLE:6,6-Ethylenedioxy-3-tert.-butyldimethylsilyl-20s-formyl-5alpha -pregnane. USE:A synthetic intermediate of brassinolides, plant growth-accelerating hormones. It permits brassinolides to be synthesized in high efficiency. PREPARATION:After ketalization of the oxo group in the 6-position of the compound of formula II as a starting substance, the hydroxyl in the 3-position is protected with a silyl, t-butyl or trityl group in the resultant product of formula III. The protected compound of formula IV is oxidized with ozone and the ozonide is reductively decomposed by addition of dimethyl sulfide to give the compound of formula I.
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