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.
一系列20R和20S乙酰胺衍
生物VIII-XI的对映体已通过氧
肟化合物I、III、IV和VI的还原和随后的乙酰化制备。它们在C-20处的绝对构型(分别为系列a和b的20R和20S)已根据它们的物理和光谱特性进行了推测。通过从具有已知C-20构型的酸XIIa和XIIb分别合成乙酰胺衍
生物Xa和Xb,证实了这种分配的正确性。