Different bio/Lewis acid-catalyzed stereoselective aldol reactions in various mediums

Abstract

In this work eight different crude biocatalysts together with six Lewis and three Bronsted acids were used for asymmetric aldol reactions of aromatic, heteroaromatic, cyclic, and acyclic six ketones and eleven aldehydes. Optimum reaction conditions were determined by changing temperature and enzyme, ketone, aldehyde, solvent, cofactors types, amounts, and ratios. PPL (porcine pancreatic lipase) of animal and AL-AN (amano lipase A from Aspergillus niger) of fungal origins were the best ones and compared with each other. CoCl2 was the best cofactor and catalyzed the enzymatic aldol reaction better than without cofactor. CoCl2 was not used before for enzymatic aldol reactions. The method in this study, using crude biocatalysts (PPL or AL-AN) and CoCl2 in acetonitrile-water was found as an conventionally useful biocatalytic way for asymmetric aldol reaction and has given better ee values than in the literature.