Facially ControlledC-Methylation of Oxolanyl and Cyclopentyl Acetate Enolates: Application to the Total Synthesis of (+)-Nephromopsinic Acid
作者:Johann Mulzer、Ulrich Steffen、Harry J. Martin、Ludwig Zorn
DOI:10.1002/ejoc.200400653
日期:2005.3
The stereoselectivity of the C-methylation of oxolanyl and cyclopentyl acetate enolates 5a–22a was investigated. The configuration of the C-methyl diastereomers was elucidated by a combination of crystal structure analysis, NMR spectroscopy and chemical correlations. Generally, the methylation proceeded re*-selectively, although with very different degrees of selectivity. The most important stereodirecting
研究了氧杂戊环和乙酸环戊酯烯醇化物 5a-22a 的 C-甲基化的立体选择性。C-甲基非对映异构体的构型通过晶体结构分析、核磁共振光谱和化学相关性的组合来阐明。通常,甲基化是重新选择性地进行的,尽管选择性程度非常不同。最重要的立体定向效应是由 5-苯乙基取代基产生的立体定向效应,并且这种立体定向效应因 3-OR 基团的立体定向效应而显着增强。与先前的文献证据相反,内环氧戊二烯基氧不发挥作用。这些发现被应用于 (+)-肾胞芘酸的高度立体选择性合成 (94)。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)