17-alpha-20 keto steroids of the (19-nor) pregnane - series

摘要

They are prepared by the action of the concentrated strong acid on the corresponding 20-acyloxy-17 alpha, 20-epoxysteroid. The transposition is suitably effected a solvent inert to the strong acid e.g. CH2Cl2, CCl4, C6H6 or in a carboxylic acid or anhydride, at temperatures between 0 degree C. and the b.pt. of the solvent, pref. at room temp. Strong acids which may be used include e.g. p-toluene sulphonic acid, styrene sulphone based ion exchange resins, and Lewis acids, as well as the usual organic and inorganic acids.