A thirteen-step synthesis of 3β,5,19-trihydroxy-5β, 14α-card-20(22)-enolide (I, title compound) from 3β-acetoxy-5-pregnen-20-one (V) is described. A characteristic feature of this approach is the introduction of the 5β-hydroxyl group by hypobromous acid addition to the 5,6-unsaturated-19-acetoxy derivative XV which proceeds with 6(O)π n participation of the acetoxy group (XV(r)XVI(r)XVII).
这是一个从3β-乙酰
氧基-5-孕烷-20-
酮(V)合成3β,5,19-
三羟基-5β,14α-环
氧-20(22)-
烯内
酯(I,标题化合物)的十三步合成过程。这种方法的一个特点是通过
次溴酸加成到5,6-不饱和-19-乙酰
氧基衍
生物XV引入5β-羟基,该过程中的乙酰
氧基(XV(r)XVI(r)XVII)参与了6(O)πn。