Synthetic studies on spirovetivane phytoalexins. V. A stereoselective total synthesis of (.+-.)-oxylubimin.
作者:Chuzo IWATA、Yoshiji TAKEMOTO、Hitoshi KUBOTA、Takeshi KURODA、Takeshi IMANISHI
DOI:10.1248/cpb.38.361
日期:——
(±)-Oxylubimin (4), the most highly oxygenated spirovetivane phytoalexin, was synthesized stereoselectively from a key intermediate, (2RS, 5RS, 9SR, 10RS)-9-hydroxy-6, 10-dimethyl-2-pivaloyloxyspiro[4.5]dec-6-en-8-one (3). Its methoxymethyl ether (8) was reduced with NaBH4 and CeCl3·7H2O to give predominantly the desired alcohol (9a) (9a/9b=6.4). The alcohol (9a) was successfully transformed into oxylubimin (4) via several steps, involving introduction of a bis(ethoxycarbonyl)methyl group at the C2, catalytic hydrogenation of the C6-C7 double bond, and pyridinium chlorochromate oxidation of the hydroxymethyl group at C6.
(±)-Oxylubimin(4)是含氧量最高的螺维烷植物毒素,由关键中间体(2RS, 5RS, 9SR, 10RS)-9-羟基-6, 10-二甲基-2-新戊酰氧基螺[4.5]癸-6-烯-8-酮(3)立体选择性合成。其甲氧基甲基醚(8)用 NaBH4 和 CeCl3-7H2O 还原,主要得到所需的醇 (9a)(9a/9b=6.4)。醇 (9a) 经过几个步骤成功地转化成了草乌甲素 (4),其中包括在 C2 处引入双(乙氧基羰基)甲基,催化 C6-C7 双键的氢化,以及氯铬酸吡啶鎓氧化 C6 处的羟甲基。