乙酸酐 、
3β,16α,20β-trihydroxypregn-5-en-18-al 20,18-hemiacetal 在
吡啶 作用下,
生成 Acetic acid (3R,3aS,4R,5aS,5bR,9S,11aR,11bS,13aR)-4,9-diacetoxy-3,11a-dimethyl-3a,4,5,5a,5b,6,8,9,10,11,11a,11b,12,13-tetradecahydro-3H-2-oxa-pentaleno[1,6a-a]phenanthren-1-yl ester