Enzymatic asymmetric synthesis of all stereoisomers of aliphatic, vicinal diols in conventional and non-conventional media

Chiral, vicinal diols are of high interest for academic research and industrial applications. For synthesizing chiral diols, enzymes are important catalysts due to their high selectivity and ability to work under tolerable temperature and no pressure. In this study, two consecutive enzyme-catalyzed steps were used for the asymmetric synthesis of aliphatic, vicinal diols with high product concentrations and chiral purity. The reaction comprised a ligation step employing lyases and a subsequent reduction step using oxidoreductases. Either in an aqueous buffer or an organic solvent, the potentially biobased aldehydes acetaldehyde, propanal, butanal, and pentanal were used as substrates. Here, all possible stereoisomers of 2,3-butanediol, 3,4-hexanediol, 4,5-octanediol, and 5,6-decanediol were produced with isomeric content values between 72% and > 99%, and concentrations and conversions between 4.1 and 60 mM. This work shows how four symmetric, chiral, vicinal diols can be synthesized by combining enzymes in a modular way, including exemplarily scaling.