Enantioselective, Catalytic One-Pot Synthesis of gamma-Butyrolactone-Based Fragrances

摘要

Herein the preparative (1 g scale), stereoselective syntheses of various alkyl-substituted gamma-butyrolactone fragrances 1 is described. The alpha,beta-unsaturated gamma-keto esters 2 as starting materials were synthesized by a Horner-Wadsworth-Emmons reaction and are further reduced by an ene reductase and alcohol dehydrogenase in a one-pot enzyme cascade to nine desired gamma-butyrolactones 1, among them whisky (1 c) and cognac lactone (1 d). The products 1 were obtained in moderate to good yields and very good diastereoselectivities. Furthermore, the position of a Bu-n-substituent was permutated to study the effect on the enzyme cascade.