A METHOD OF CONTROLLING THE EMPIMERIC DISTRIBUTION IN THE PREPARATION OF 16,17-ACETALS OR KETALS OF PREGNANE DERIVATIVES

摘要

A method of controlling the epimeric distribution in the preparation of 16,17-acetals of pregnane derivatives characterized in reaction of a corresponding 16,17-acetonide with an aldehyde or ketone in a) hydrocarbon solvent wherein the solubility of the pregnane derivative is less than 1 mg/l or in a halogenated hydrocarbon solvent together with a hydrohalogen acid or an organic sulphonic acid as catalyst and in the presence of small grains of an inert material in the reaction medium or b) a halogenated hydrocarbon solvent together with a hydrohalogen acid an organic sulphonic acid as catalyst and in the presence of an epimeric distribution modifier.