Asymmetric Synthesis of 2-Keto-1,3-diols and Protected 1,2,3-Triols Bearing Two Quaternary Stereocenters
作者:Dieter Enders、Irene Breuer、Gerhard Raabe
DOI:10.1055/s-2005-918425
日期:——
The asymmetric synthesis of 1,3-dihydroxy-2-ketones bearing two quaternary stereocenters in α- and α′-position starting from 2,2-dimethyl-1,3-dioxan-5-one-SAMP-hydrazone is described. The protocol involves four consecutive α/α′-alkylations, the last one being carried out in the presence of DMPU as additive. After acidic cleavage of both the chiral auxiliary and the acetal function in a two-phase system, the title compounds are obtained with high stereoselectivity (de ≥ 91-97%, ee ≥ 96%) and in moderate to very good overall yields (14-61%). In addition, 1,2-quaternary 1,3-protected 1,2,3-triols were obtained by nucleophilic 1,2-addition to the carbonyl group as single stereoisomeres (de, ee ≥ 96%) in excellent yields.
本论文介绍了以 2,2-二甲基-1,3-二氧杂环-5-酮-SAMP-腙为起点,不对称合成在δ-和δ±′-位上具有两个季立体中心的 1,3-二羟基-2-酮的方法。该方案包括四个连续的δ±/δ±′-烷基化反应,最后一个反应是在添加剂 DMPU 的情况下进行的。在两相体系中对手性助剂和缩醛功能进行酸性裂解后,得到的标题化合物具有很高的立体选择性(de ≥ 91-97%,ee ≥ 96%),总产率从中等到非常好(14-61%)。此外,通过亲核 1,2- 添加到羰基上得到了 1,2-季 1,3-保护的 1,2,3-三醇单立体异构体(de,ee ≥ 96%),收率极高。