EP0875516A2 — Process for the preparation of 16,17 acetals of pregnane derivatives with control of the epimeric distribution at the C-22 position

USPTO Abstract

Described herein is a process for the preparation of an acetal of formula (I) in which R 1 is an alkyl, R 2 is H or an acyl, X is β-OH and Y is H, comprising the acetalization with control of the epimeric distribution at the C-22 position, for treatment with R 1 CHO in aqueous HBr or HI of a compound of formula (II) in which R 2 has the meaning specified above, R 3 and R 4 are both H, or, taken together, are -C(R 5 )(R 6 )-, where R 5 and R 6 , which may be the same or different from one another, are alkyl groups, and X and Y are chosen from among the following: A) X and Y, taken together, are an additional bond between C-9 and C-11; B) X is β-OH, and Y is H or an α-halogen; C) X is β-OR 7 where R 7 is an acyl, and Y is H or an α-halogen; and D) X and Y, taken together, are -O-.