Preparation of 20R and 20S Acetylamino-30-norlupane Derivatives

Abstract

A series of epimeric pairs of 20R and 20S acetylamino derivatives VIII-XI have been prepared by reduction and subsequent acetylation of the oximes I, III, IV and VI. Their absolute configuration at C-20 (20R and 20S for the series a and b, respectively) has been suggested on the basis of their physical and spectral properties. The correctness of this assignment was confirmed by the synthesis of the acetylamino derivatives Xa and Xb from the acids XIIa and XIIb, respectively, with known configuration at C-20.