A General Strategy for the Catalytic, Highly Enantio- and Diastereoselective Synthesis of Indolizidine-Based Alkaloids
作者:Falko Abels、Chris Lindemann、Christoph Schneider
DOI:10.1002/chem.201304086
日期:2014.2.10
Sixteen indolizidine‐based alkaloids (IBAs) that were isolated as poison constituents of the skin of frogs were synthesized in a highly flexible and stereoselective manner. As a key step, a three‐component, organocatalytic, highly enantio‐ and diastereoselective vinylogous Mukaiyama–Mannich reaction was employed furnishing optically highly enriched butyrolactams as central intermediates on a multigram
以高度灵活和立体选择性的方式合成了十六种基于吲哚并立定的生物碱(IBA),它们是青蛙皮肤的有毒成分。作为关键步骤,采用了三组分,有机催化,高度对映和非对映选择性的乙烯基Mukaiyama-Mannich反应,以克数形式提供了光学高度浓缩的丁内酰胺作为中心中间体。通过将烯醇侧链部分环化到吡咯烷环上来构建连接的六元环。桥头手性中心和相邻8位的绝对构型是在最初的乙烯基曼尼希反应中确定的,而3和5位取代基是在合成的后期通过有机金属加成引入的,并从底物上进行了完全的立体化学控制。通过这种策略,可将简单甚至更复杂的生物碱作为单一的立体异构体以较高的总收率获得。这些合成还有助于建立那些以前从未合成过的IBA的绝对和相对构型。