Stereocontrolled Syntheses of (−)-Cubebol and (−)-10-Epicubebol Involving Intramolecular Cyclopropanation of α-Lithiated Epoxides
作者:David M. Hodgson、Saifullah Salik、David J. Fox
DOI:10.1021/jo9022974
日期:2010.4.2
syntheses of 7-epicubebol (33) and (from (+)-menthone) of naturally occurring (−)-10-epicubebol (39), confirming the original structural assignment. Computational studies support the origin of the inversion as being rate-determining formylation of cis-enolate 27 from a mixture of rapidly interconverting enolates. In the synthesis of 7-epicubebol (33), allylic tertiary C−H insertion is observed as a significant
(-)-薄荷酮(11)与LDA和HCO 2 CH 2 CF 3的甲酰化避免了在异丙基上的构型完整性的损失,从而获得了羟甲基薄荷酮12。锂2,2,6,6-四甲基哌啶诱导的衍生的不饱和末端环氧化物17(和氯代醇16)的分子内环丙烷化反应有效地生成了取代的三环[4.4.0.0 1,5 ] decan-4-ol 18,用于(-)-cubebol(1)的简明合成。相比之下,薄荷酮与NaOMe和HCO 2甲酰化过程中的异丙基转化通过类似的策略,Et导致了7-epicubebol(33)和(来自(+)-薄荷脑)天然存在的(-)-10-epicubebol(39)的合成,从而确认了原始的结构分配。计算研究支持反演的起源,因为它是由快速相互转化的烯醇混合物决定速率确定顺式-烯醇酸酯27的甲酰化的方法。在7-epicubebol(33)的合成中,在不饱和末端环氧化物22的分子内环丙烷化反应中,烯丙基叔CH的插入是一种重要的竞争反应。