| 摘要 |
The novel compounds 3b -hydroxy-11-keto-5,17(20)[cis] - pregnadien - 21 - oic acid methyl ester, 3b - hydroxy - 5a ,6a - epoxy - 11 - keto - 17(20)[cis] - pregnen - 21 - oic acid methyl ester and 3b ,5a - dihydroxy - 6b - fluoro - 11 - keto - 17(20)[cis] - pregnen - 21 - oic acid methyl ester, and other C2- 8 alkyl esters are prepared by reacting 3b -hydroxy-5-pregnene-11,20-dione or the corresponding isopregnene or mixtures thereof with a dialkyl oxalate and an alkali metal base to produce the corresponding 21-alkyloxyoxalyl alkali metal enolates, converting these with bromine, chlorine or iodine in the presence of a base into the corresponding 21,21-dihalo-21-alkoxyoxalyl compounds, hydrolysing these with an alkali metal alkoxide and an alkanol to give the required D 5-compounds, epoxidizing these to give the required epoxides, and reacting these with hydrogen fluoride to give the required 6b -fluoro-compounds. These may then be oxidized to the corresponding 3-ketones. 5b ,6b -epoxides are by-products of the epoxidation reaction, and these are removed by conventional methods. Examples are given, an intermediate in the halogenation stage being a 5,6-dibromo compound which is reconverted to the required D 5-compound by reduction with zinc and acetic acid.
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