A convenient synthetic method for the marine antibiotic (−)-malyngolide and its stereoisomers was accomplished from a chiral α-alkoxyketone (4), which was readily available as a chiron. Chiral quaternary carbon synthons (5a) and (5b) as the key intermediates were constructed by the chelation controlled addition of Grignard reagent to 4.The diastereomeric mixture of 5a and 5b was readily transformed into a separable mixture of lactones (7a) and (7b), each of which could be easily separated by silica-gel column chromatography. (−)-Malyngolide and its three steroisomers were obtained in optically pure form without the need for optical resolution.
一种简便的海洋抗生素(−)-马灵果内酯及其立体异构体的合成方法得以实现,该方法从易于获得的手性α-烷氧基酮(4)作为起始物出发。通过
格氏试剂对4的螯合控制加成,构建了手性四级碳合成子(5a)和(5b)作为关键中间体。5a和5b的非对映异构体混合物可方便地转化为可分离的内酯混合物(7a)和(7b),二者均可通过
硅胶柱层析轻松分离。(−)-马灵果内酯及其三种立体异构体以光学纯形式获得,无需进行光学拆分。