Alkyl Formate Ester Synthesis by a Fungal Baeyer–Villiger Monooxygenase

We investigated Baeyer–Villiger monooxygenase (BVMO)‐mediated synthesis of alkyl formate esters, which are important flavor and fragrance products. A recombinant fungal BVMO from Aspergillus flavus was found to transform a selection of aliphatic aldehydes into alkyl formates with high regioselectivity. Near complete conversion of 10 mm octanal was achieved within 8 h with a regiomeric excess of ∼80 %. Substrate concentration was found to affect specific activity and regioselectivity of the BVMO, as well as the rate of product autohydrolysis to the primary alcohol. More than 80 % conversion of 50 mm octanal was reached after 72 h (TTN nearly 20 000). Biotransformation on a 200 mL scale under unoptimized conditions gave a space‐time yield (STY) of 4.2 g L−1 d−1 (3.4 g L−1 d−1 extracted product). Choosing sides: Alkyl formate synthesis is performed with a Baeyer–Villiger monooxygenase. Regioselectivity and rate of autohydrolysis of the alkyl formates to the corresponding primary alcohol product is affected by substrate concentration.