Enantioselective Bioamination of Aromatic Alkanes Using Ammonia: A Multienzymatic Cascade Approach

Abstract

AbstractChiral amines are common drug building blocks and important active pharmaceutical ingredients. Preparing these functionalized compounds from simple materials, such as alkanes, is of great interest. We recently developed an artificial bioamination cascade for the C−H amination of cyclic alkanes by combining P450 monooxygenase, alcohol dehydrogenase, and amine dehydrogenase. Herein, this system has been extended to the synthesis of chiral aromatic amines. In the first hydroxylation step, process optimization increased the conversion to 77 %. Two stereoselectively complementary alcohol dehydrogenases and an amine dehydrogenase were selected for the bioconversion of aromatic hydrocarbons to amines. The amination reaction was optimized with respect to cofactor addition and enzyme dosage. Isopropanol was added to decrease ketone intermediate accumulation in the amination step, which further enhanced the overall conversion. This cascade system converted a panel of hydrocarbon substrates into the corresponding amines with excellent optical purity (>99 % ee) and moderate conversion ratios (13–53 %).