Chemoenzymatic Synthesis of Indole-Containing Acyloin Derivatives

Indole-containing acyloins are either key intermediates of many antimicrobial/antiviral natural products or building blocks in the synthesis of biologically active molecules. As such, access to structurally diverse indole-containing acyloins has attracted considerable attention. In this report, we present a pilot study of using biotransformation to provide acyloins that contain various indole substituents. The biotransformation system contains the tryptophan synthase standalone β-subunit variant, PfTrpB⁶, generated from directed evolution in the literature; a commercially available L-amino acid oxidase (LAAO); and the thiamine-diphosphate (ThDP)-dependent enzyme NzsH, encoded in the biosynthetic gene cluster (nzs) of the bacterial carbazole alkaloid natural product named neocarazostatin A. The utilization of the first two enzymes, the PfTrpB variant and LAAO, is designed to provide structurally diverse indole 3-pyruvate derivatives as donor substrates for NzsH-catalysed biotransformation to provide acyloin derivatives. Our results demonstrate that NzsH displays a considerable substrate profile toward donor substrates for production of acyloins with different indole ring systems, suggesting that NzsH could be further explored as a potential biocatalyst via directed evolution to improve the catalytic efficiency in the future.