49 ブレフェルディンAの合成

概要

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Brefeldin A (1), a fungal metabolite, was stereoselectively synthesized as described below. The starting keto dicarboxylic acid (5) which is a degradation product of 1, was prepared from citric acid by the known method and was converted into the aldehyde (11), which had proper steric configurations for further transformation. Reaction of 11 with vinyl magnesium bromide gave the allyl alcohol (15), which was then submitted to claisen rearrangement to give the mixture of two aldehydes (17 and 18). In the next Wittig condensation with α-methoxyethylidenetriphenyl-phosphorane, only the trans-aldehyde (17) reacted to give the desired enol ether (19) as a sole product. Hydrolysis of 19 gave the methylketone (20), which was converted into the Corey's key intermediate (22) by successive reduction, protection, hydrolysis and reprotection. The carboxylic acid obtained from 22 by hydrolysis, was converted into the ylid (24) and was further condenced with ethyl glyoxylate. The enone (25) thus obtained was transformed into the hydroxy acid (2b). For the lactonization of 2b, a method previously developed by our group was used. The lactone (27) thus obtained had already been converted into 1 by Corey and Wollenberg.
天然有機化合物討論会の論文
1979-09-20