Bioproduction of Enantiopure (R)‐ and (S)‐2‐Phenylglycinols from Styrenes and Renewable Feedstocks

Abstract

AbstractEnantiopure (R)‐ and (S)‐2‐phenylglycinols are important chiral building blocks for pharmaceutical manufacturing. Several chemical and enzymatic methods for their synthesis were reported, either involving multi‐step synthesis or starting from a relatively complex chemical. Here, we developed one‐pot simple syntheses of enantiopure (R)‐ and (S)‐2‐phenylglycinols from cheap starting materials and renewable feedstocks. Enzyme cascades consisting of epoxidation‐hydrolysis‐oxidation‐transamination were developed to convert styrene 2 a to (R)‐ and (S)‐2‐phenylglycinol 1 a, with butanediol dehydrogenase for alcohol oxidation as well as BmTA and NfTA for (R)‐ and (S)‐enantioselective transamination, respectively. The engineered E. coli strains expressing the cascades produced 1015 mg/L (R)‐1 a in >99% ee and 315 mg/L (S)‐1 a in 91% ee, respectively, from styrene 2 a. The same cascade also converted substituted styrenes 2 b–k and indene 2 l into substituted (R)‐phenylglycinols 1 b–k and (1R, 2R)‐1‐amino‐2‐indanol 1 l in 95–>99% ee. To transform bio‐based L‐phenylalanine 6 to (R)‐1 a and (S)‐1 a, (R)‐ and (S)‐enantioselective enzyme cascades for deamination‐decarboxylation‐epoxidation‐hydrolysis‐oxidation‐transamination were developed. The engineered E. coli strains produced (R)‐1 a and (S)‐1 a in high ee at 576 mg/L and 356 mg/L, respectively, from L‐phenylalanine 6, as the first synthesis of these compounds from a bio‐based chemical. Finally, L‐phenylalanine biosynthesis pathway was combined with (R)‐ or (S)‐enantioselective cascade in one strain or coupled strains, to achieve the first synthesis of (R)‐1 a and (S)‐1 a from a renewable feedstock. The coupled strain approach enhanced the production, affording 274 and 384 mg/L (R)‐1 a and 274 and 301 mg/L (S)‐1 a, from glucose and glycerol, respectively. The developed methods could be potentially useful to produce these high‐value chemicals from cheap starting materials and renewable feedstocks in a green and sustainable manner.magnified image