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, Pf TrpB 6 , 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 Pf TrpB 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.