作者:Mohamad R. Agharahimi、Norman A. LeBel
DOI:10.1021/jo00111a052
日期:1995.3
(-)-Monoterpenylmagnolol (3) was synthesized in eight steps from (+)-3,9-dibromocamphor (4) and the bis(methoxymethyl) ether (22) of 3-(4-hydroxyphenyl)-1-propanol. Fragmentation of an endo-3-aryl-9-bromocamphor (27) provided the correct absolute stereochemistry. In this total synthesis, dissolving metal conditions were developed to reduce enol phosphate and isopropenyl functions without concomitant reduction of an attached phenol. Palladium(O)-catalyzed cross-coupling of an arylzinc chloride with 4-allyl-2-iodophenyl methoxymethyl ether (34) provided the desired tricyclic 1,2,3,5-tetrasubstituted biaryl 41 in fair yield without optimization and with little isomerization of the allyl group. Magnolol (1) was also synthesized by aryl coupling of 34 and the methoxymethyl ether of 4-allyl-2-lithiophenol via the zinc chloride method as above, as well as from 5,5'-dibromo-2,2'-dimethoxybiphenyl (37) by allylation with allyltributylstannane followed by ether cleavage.
(-)-单萜烯基黄素醇 (3) 由 (+)-3,9-二溴化樟脑 (4) 和 3-(4-羟基苯基)-1-丙醇的双(羟甲基)醚 (22) 经过八步合成。 内-3-取代苯基-9-溴化樟脑 (27) 的断裂提供了正确的绝对构型。 在此全合成中,开发了可溶金属还原条件,用于分别还原烯醇磷酸盐和异丙烯基功能,而不会同时还原连接的酚羟基。 通过钯 (0) 催化的芳基氯化锌与 4-烯丙基-2-碘苯基羟甲基醚 (34) 的交叉偶联,得到了预期的三环 1,2,3,5-四取代联苯 41,产率尚可,未经优化且烯丙基异构化很少。 另外,还通过锌氯化物法将 34 和 4-烯丙基-2-锂代苯酚的羟甲基醚进行偶联,以及由 5,5’-二溴-2,2’-二甲氧基联苯 (37) 通过与烯丙基三丁基锡进行烯丙基化反应后再进行醚键裂解,合成了黄素醇 (1)。