One‐Pot Enantioselective Synthesis of d ‐Phenylglycines from Racemic Mandelic Acids, Styrenes, or Biobased l ‐Phenylalanine via Cascade Biocatalysis

Enantiopure d ‐phenylglycine and its derivatives are an important group of chiral amino acids with broad applications in thepharmaceutical industry. However, the existing synthetic methods for d ‐phenylglycine mainly rely on toxic cyanide chemistry and multistep processes. To provide green and safe alternatives, we envisaged cascade biocatalysis for the one‐pot synthesis of d ‐phenylglycine from racemic mandelic acid, styrene, and biobased l ‐phenylalanine, respectively. Recombinant Escherichia coli (LZ110) was engineered to coexpress four enzymes to catalyze a 3‐step reaction in one pot, transforming mandelic acid (210 mM) to give enantiopure d ‐phenylglycine in 29.5 g L −1 (195 mM) with 93% conversion. Using the same whole‐cell catalyst, twelve other d ‐phenylglycine derivatives were also produced from the corresponding mandelic acid derivatives in high conversion (58–94%) and very high ee (93–99%). E. coli (LZ116) expressing seven enzymes was constructed for the transformation of styrene to enantiopure d ‐phenylglycine in 80% conversion via a one‐pot 6‐step cascade biotransformation. Twelve substituted d ‐phenylglycines were also produced from the corresponding styrene derivatives in high conversion (45–90%) and very high ee (92–99%) via the same cascade reactions. A nine‐enzymeexpressing E. coli (LZ143) was engineered to transform biobased l ‐phenylalanine to enantiopure d ‐phenylglycine in 83% conversion via a one‐pot 8‐step transformation. Preparative biotransformations were also demonstrated. The high‐yielding synthetic methods use cheap and green reagents (ammonia, glucose, and/or oxygen), and E. coli whole‐cell catalysts, thus providing green and useful alternative methods for manufacturing d ‐phenylglycine.