| 摘要 |
The invention comprises the 11,18-lactones of 11b - hydroxy - 16a -methyl-5b -pregnan-18b -oic acid of the formula: <FORM:0903808/IV (b)/1> where R represents a hydrogen atom or an acyl radical and processes for the preparation thereof in which a 3a -acyloxy-16a -methyl-5b -pregna-11,20-dione is reduced to give 3a -acyloxy - 16a - methyl - 20-hydroxy-5b -pregnan-11-one, which is reacted with lead tetracetate to yield a 3a -acyloxy-16a -methyl-18,20-epoxy-5b -pregnan-11-one and this latter compound is oxidised and saponified to yield 3a ,20-dihydroxy-16a -methyl-18,20-epoxy - 5b - pregna-11,18-dione which is then reduced and treated with acid to form the 11,18-lactone of 3a , 11b , 20b -trihydroxy-16a -methyl - 5b - pregnan - 18b -oic acid. The latter compound may be esterified to obtain the corresponding 11,18-lactone of 3a ,20b - diacyloxy-11b -hydroxy-16a -methyl-5b -pregnan-18b -oic acid. The reductive steps may be effected with lithium aluminium hydride and the oxidation step with chromic acid. |
