Total Biocatalytic Synthesis of Capsaicinoids Using Ferulic Acid: A Versatile Two‐Step Strategy for Natural Product Diversification

Abstract The wide‐ranging application of capsaicinoids, the active compounds in chili peppers, has driven increasing interest in the development of sustainable production strategies. However, capsaicinoid synthesis remains a challenge. The objective of this pioneering study is to report the total biocatalytic synthesis of structurally diverse capsaicinoids from bio‐based ferulic acids. An X‐ray crystallographic study elucidated the structural basis for the exceptional potential of a novel transaminase from Phaeobacter porticola (PPTA) to transform the highest ever reported concentration of vanillin (100–200 mM) to vanillylamine, with >99% conversion and modest conversion ranging from 48% to 79% for 300 to 500 mM substrate. Using PPTA in tandem with phenolic acid decarboxylase (PAD) and aromatic dioxygenase (ADO) further enabled the direct synthesis of vanillylamine from ferulic acid with >99% conversion. Furthermore, the integration of a multi‐enzymatic cascade with carboxylic acid reductases (CARs) successfully synthesized structurally diverse capsaicinoids via amide bond formation between vanillylamine and free fatty acids, with excellent conversions ranging from 72% to >88%. A 50‐mM enzymatic reaction afforded 95% and 80% conversion of vanillylamine and capsaicin, respectively.