Tyramine Derivatives Catalyze the Aldol Dimerization of Butyraldehyde in the Presence of Escherichia coli

Interfacing Whole Cell Biocatalysis with a Biocompatible Pictet-Spengler Reaction for One-Pot Syntheses of Tetrahydroisoquinolines and Tryptolines

Biocatalytic processes are highly selective and specific. However, their utility is limited by the comparatively narrow scope of enzyme-catalysed transformations. To expand product scope, we are developing biocompatible processes that combine biocatalytic reactions with chemo-catalysis in single-flask processes. Here, we show that a chemocatalysed Pictet-Spengler annulation can be interfaced with biocatalysed alcohol oxidation. This two-step, one-pot cascade reaction converts tyramine and aliphatic alcohols to tetrahydroisoquinoline alkaloids in aqueous buffer at mild pH. Tryptamine derivatives are also efficiently converted to tryptolines. Optimization of stoichiometry, pH, reaction time, and whole-cell catalyst deliver the tetrahydroisouinolines and tryptolines in >90 % and >40 % isolated yield, respectively, with excellent regioselectivity.

Biocompatible α-Methylenation of Metabolic Butyraldehyde in Living Bacteria

Small molecule organocatalysts are abundant in all living organisms. However, their use as organocatalysts in cells has been underexplored. Herein, we report that organocatalytic aldol chemistry can be interfaced with living Escherichia coli to enable the α-methylenation of cellular aldehydes using biogenic amines such as L-Pro or phosphate. The biocompatible reaction is mild and can be interfaced with butyraldehyde generated from D-glucose via engineered metabolism to enable the production of 2-methylenebutanal (2-MB) and 2-methylbutanal (2-MBA) by anaerobic fermentation, and 2-methylbutanol (2-MBO) by whole-cell catalysis. Overall, this study demonstrates the combination of non-enzymatic organocatalytic and metabolic reactions in vivo for the sustainable synthesis of valuable non-natural chemicals that cannot be accessed using enzymatic chemistry alone.