Stereoselective oxy-homo-Michael reactions of enantioenriched bicyclic donor–acceptor cyclopropanes to afford optically active trans-α,β-disubstituted γ-butyrolactones possessing three serial chiral centers

Abstract

Stereoselective oxy-homo-Michael (OHM) addition of alcohols, phenols, and carboxylic acid to optically active bicyclic donor–acceptor cyclopropanes such as (1S,5R,6S)-6-aryl-1-methoxycarbonyl-3-oxabicyclo[3,1,0]hexan-2-ones proceeded to give trans-α,β-disubstituted γ-butyrolactones, which possess three serial chiral centers, in good to high yields with excellent dr and ee. Increasing the loading of alcohols to two equivalents improved the diastereoselectivity in the reactions of bicyclic lactones bearing alkoxy substituted aryl groups. Based on the results, we proposed a plausible mechanism of the OHM reaction including SN2′-like addition of nucleophiles. The present method can be a new avenue for the asymmetric synthesis of trans-α,β-disubstituted γ-butyrolactones including various natural lignan lactones.