The thermal elimination of β-ketosulfoxide (2) afforded the α, β-unsaturated γ-ketoester (3) as a Michael acceptor (analogous to the key intermediate in Smith's estrone synthesis), which was condensed with 2-methylcyclopentane-1, 3-dione to give the adduct (4) having all carbon units of the aromatic steroidal skeleton. The Michael adduct was then cyclized in the presence of methanesulfonic acid to yield the novel estrapentaene (6) with a methoxycarbonyl group at the C-12 position. The estrapentaene (6) was converted to 12β- and 12α-methoxycarbonylestrones (25 and 26) and their estradiol derivatives (27 and 28) by selective reductions followed by demethylation.
β-酮亚砜(2)的热消除反应生成了α, β-不饱和γ-
酮酯(3),作为迈克尔受体(类似于史密斯的
雌酮合成中的关键中间体),与2-
甲基环戊烷-1, 3-二酮缩合生成了含有芳香类
固醇骨架的附加物(4)。然后,迈克尔附加物在
甲烷磺酸的存在下环化,生成了具有C-12位置甲氧基羧基的新型雌烷五烯(6)。雌烷五烯(6)经过选择性还原和去甲基化,转化为12β-和12α-甲氧基羧基
雌酮(25和26)及其
雌二醇衍
生物(27和28)。