Amide and Thioester Synthesis Via Oxidative Coupling of Alcohols with Amines or Thiols Using Alcohol Dehydrogenases.

Abstract

Amide and thioester moieties are prevalent in pharmaceuticals, natural products, and functional materials, but their chemical synthesis suffers from poor atom economy and ungreen conditions, while biocatalytic methods require ATP-dependent enzymes, activated intermediates, or show limited scope and activity. Here, we report the oxidative coupling of alcohols with ammonia or amines catalyzed by alcohol dehydrogenases (ADHs) via hemiaminal intermediates to form primary and secondary amides at pH 9.5-10.5. Pf-ADH preferably converted linear aliphatic or arylaliphatic alcohols (up to 90% conversion), while Pp-ADH and Aa-ADH preferably converted branched or aromatic alcohols (up to 99% conversion). Preparative-scale synthesis of an N-methyl amide gave >99% conversion and 87% isolated yield. The method was extended to thioacid and thioester formation via hemithioacetal intermediates using hydrogen sulfide or thiols at pH 7. Pf-ADH favored linear aliphatic alcohols (up to 93% conversion), Pp-ADH branched alcohols (up to 82% conversion), and Aa-ADH aromatic alcohols (up to 98% conversion). A KPi/MTBE biphasic system enabled the reaction with poorly soluble long-chain thiols. Structure-guided engineering of Aa-ADH led to the Y151A and L186A variants with expanded activity toward longer-chain amines or thiols. This work highlights how enzyme promiscuity with protein engineering can enable new-to-nature synthetic pathways for the production of valuable compounds.