Asymmetric synthesis of 9-alkyl tetrahydroxanthenones via tandem asymmetric Michael/cyclization promoted by chiral phosphoric acid

A tandem asymmetric Michael-addition/cyclization of cyclic 1,3-dicarbonyl compounds to beta,gamma-unsaturated alpha-ketoesters catalyzed by chiral phosphoric acid is presented. This protocol provides a facile approach for the construction of enantioenriched 9-alkyl tetrahydroxanthenones, an ubiquitous framework found in a number of natural products and pharmaceutical molecules, in high yields with good to high enantioselectivities.

报道了一种在手性磷酸催化下，环状1,3 - 二羰基化合物与β,γ - 不饱和α - 酮酯的串联不对称迈克尔加成/环化反应。该方法为构建对映体富集的9 - 烷基四氢呫吨酮提供了一种简便的途径，9 - 烷基四氢呫吨酮是一种在许多天然产物和药物分子中普遍存在的结构，该反应能以高产率和良好到较高的对映选择性得到产物。