作者:Ernst Urban、Guido Knühl、Günter Helmchen
DOI:10.1016/0040-4020(95)00834-u
日期:1995.11
(-)-Chokol A (10) was prepared in six steps (22% overall yield) via conjugate addition of a higher order cyanocuprate to the chiral 2-oxo-cyclopentenecarboxylate 2n After deprotection by transesterification the enantiomerically pure β-ketoester 5 was obtained which was transformed by α-methylation and subsequent decarbethoxylation to the cyclopentanone derivative 8. Addition of methylcerium dichloride
( - ) - Chokol A(10)在通过共轭加成高阶cyanocuprate的手性2-氧代cyclopentenecarboxylate六个步骤(22%总产率)中的溶液制备的2n通过酯交换反应脱保护后的对映体纯β酮酯5得到通过α-甲基化和随后的脱碳乙氧基化将其转化为环戊酮衍生物8。加入二氯化甲基铈产生9a,9b和9c的混合物(78:16:6),通过MPLC从其中分离出主要的非对映异构体9a。最终9a的甲硅烷基化获得了(-)-chokol A(10)。