An asymmetric formal synthesis of the fungal metabolites ()-cryptosporiopsin and ()-3-deschloro crypto sporiopsin has been accomplished. The asymmetry was introduced via a diastereoselective [2+2]-cycloaddition between an enoxy-ester, bearing a bulky chiral auxiliary, and dichloroketene. Diastereomeric ratios of 10:1 were obtained from the reaction mixture, but this could be increased by simple crystallization. Completion of the synthesis was only accomplished after the serendipitous discovery of a base-catalyzed rearrangement to furnish the requisite 3-chloroenone moiety.Key words: diastereoselective [2+2]-cycloaddition, rearrangement, chiral auxiliary.
通过非对称正式合成,成功合成了真菌代谢物(-)-cryptosporiopsin和(-)-3-deschloro crypto sporiopsin。通过在带有笨重手性辅助剂的烯氧基酯和二氯甲酮之间进行对映选择性的[2+2]-环加成引入了不对称性。反应混合物中获得了10:1的对映异构比,但可以通过简单结晶来增加。合成的完成仅在偶然发现碱催化重排以提供所需的3-氯酮基团之后才实现。关键词:对映选择性[2+2]-环加成,重排,手性辅助剂。