Synthesis of enantiopure (S)‐6‐chlorochroman‐4‐ol using whole‐cell Lactobacillus paracasei biotransformation

Abstract

Chromane, which has a fused cyclic structure, is a significant molecule that can be found in the structure of many important compounds. Lactobacillus paracasei BD101 was demonstrated as whole‐cell biocatalyst for the synthesis of (S)‐6‐chlorochroman‐4‐ol with immense enantioselectivity. The conditions of asymmetric reduction were optimized one factor by one factor using L paracasei BD101 to achieve enantiomerically pure product and complete conversion. Using these obtained optimization conditions, asymmetric reduction of 6‐chlorochroman‐4‐one was performed under environmentally friendly conditions; 6‐chlorochroman‐4‐one, having a fused cyclic structure as previously noted to be difficult to asymmetric reduction with biocatalysts, was enantiomerically reduced to (S)‐6‐chlorochroman‐4‐ol with an enantiomeric excess >99% on a high gram scale. This study is the first example in the literature for the enantiopure synthesis of (S)‐6‐chlorochroman‐4‐ol using a biocatalyst. Also notably, the optical purity of (S)‐6‐chlorochroman‐4‐ol obtained in this study through asymmetric bioreduction using whole‐cell biocatalyst is the highest value in the literature. In this study, (S)‐6‐chlorochroman‐4‐ol was produced on a gram scale by an easy, inexpensive, and environmentally friendly method, which has shown the production of valuable chiral precursors for drug synthesis and other industrial applications. This study provides a convenient method for the production of (S)‐6‐chlorochroman‐4‐ol, which can meet the industrial green production demand of this chiral secondary alcohol.