In order to determine the precursor role of neutral steroids in the formation of estetrol in man the titled compound was prepared as a substrate by two different routes. First, 17, 17-ethylenedioxy-5α-androst-15-ene-3β, 5-diol (I), readily available by the known method, was employed as a starting material. Transformation into the 15α, 16α-glycol structure was attained by osmium tetroxide oxidation toward the Δ15 double bond. Dehydration with thionyl chloride provided a mixture of the Δ4 and Δ5-3β, 15α, 16α, 17β-tetraols (V), which was in turn led to the 15, 16-acetonide (VI). Oppenaner oxidation followed by removal of the dioxolane group afforded the Δ4-3-ketosteroid (VIIIa). Alternatively, 3β, 5β-dihydroxyandrost-15-en-17-one ethylene ketal (XIV), derivable from dehydroepiandrosterone in several steps, was similarly converted into androst-4-ene-3β, 15α, 16α, 17β-tetraol (XXa). Selective oxidation of the hydroxylic group at C-3 with N-bromoacetamide provided the desired compound (VIIIa). The latter synthetic route has proved to be more favorable in respect to overall yield.
为了确定中性类
固醇在人体内形成
雌三醇过程中的前体作用,我们通过两种不同的方法制备了标题化合物作为底物。首先,采用已知方法容易获得的 17,17-亚乙二氧基-5α-雄甾-15-烯-3β,5
-二醇(I)作为起始原料。通过
四氧化锇向 Δ15 双键氧化,转化成 15α、16α-
乙二醇结构。用亚
硫酰氯脱
水后,得到了 Δ4和Δ5-3β、15α、16α、17β-四醇的混合物(V),进而得到了 15、16-
丙酮(VI)。通过奥本纳氧化,然后去除二
氧戊环基团,可得到Δ4-3-酮
甾醇(VIIIa)。另外,3β,5β-二羟基雄甾-15-烯-17-酮亚乙基
缩酮(XIV)可通过几个步骤从脱氢
表雄酮衍生出来,同样可转化为雄甾-4-烯-3β,15α,16α,17β-四醇(XXa)。用 N-
溴乙酰胺对 C-3 处的羟基进行选择性氧化,可得到所需的化合物(VIIIa)。事实证明,后一种合成路线在总收率方面更为有利。