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

Abstract

Enantiopure (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 biobased L-phenylalanine 6 to (R)-1 a and (S)-1 a, (R)-and (S)-enantioselective enzyme cascades for deaminationdecarboxylation-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.

Engineering of Cascade Reactions and Alditol Oxidase for High‐Yielding Synthesis of (R)‐Phenylethanolamine from Styrene, l‐Phenylalanine, Glycerol or Glucose

“…A number of enzyme cascades have been reported for the production of high‐value chiral chemicals such as ( S )‐, and ( R )‐mandelic acid (MA), [22] ( S )‐, and ( R )‐phenylglycine, [18c,23] ( S )‐ and ( R )‐2‐phenylglycinol, [24] and ( S )‐PEA [18a] from simple and cheap chemicals. However, no enzyme cascade for the conversion of styrene, l ‐Phe, glycerol or glucose to ( R )‐PEA has been reported so far.…”

Chemoenzymatic Synthesis of Enantiopure Amino Alcohols from Simple Methyl Ketones

“…[7] Enzymes for these reactions are lipases (kinetic resolution only) and primarily transaminases and amine dehydrogenases, whereby an amino group is transferred to a carbonyl substrate. [1,[8][9][10][11]12,[13][14][15][16] For asymmetric synthesis, transaminase-and amine dehydrogenase-catalyzed reactions require additional methods for shifting the equilibrium to the product side. This includes the use of enzyme cascades, cofactor regeneration with irreversible steps or the specific removal of the product directly from the reaction solution, e. g. via crystallization or membrane processes.…”

Cascade Biotransformations for Enantioconvergent Conversion of Racemic Styrene Oxides to (R)-Mandelic Acids

“…Enzymatic cascades involving multiple enzymes in one pot allow for direct syntheses of valuable enantiopure chemicals from cheap starting materials. − In addition to the use of nonchiral substrates, the use of easily available racemic substrates for enantioconvergent cascade conversion to enantiopure chemicals , has been receiving increasing attention. We are interested in developing a new enantioconvergent cascade to convert racemic epoxides into the corresponding enantiopure hydroxy acids.…”