Asymmetric Dehydration of β-Hydroxy Esters and Application to the Syntheses of Flavane Derivatives.

Abstract Catalytic asymmetric dehydration of β-aryl or alkyl substituted β-hydroxy esters via kinetic resolution has been investigated. A brief survey of 10 different chiral ligands is conducted to examine the effects of chiral ligand structure on selectivity of the dehydration. The kinetic resolution of a variety of rac -β-hydroxy tert -butyl esters in the presence of prolinol chiral ligand 2 and BrZnCH 2 CO 2 - t -Bu can provide highly enantioenriched β-hydroxy esters 14 – 21 with selectivity factors ranging from 11 to 66. Also, application of this asymmetric synthetic methodology to the preparation of enantioenriched flavane derivatives 25 – 29 is demonstrated.