(R)-(+)-2-(4-Hydroxyphenoxy)propionic Acid is a degradation product of Cyhalofop-butyl (C989385); an aryloxyphenoxypropionate compound that is used as a herbicide to eliminate grass weeds in rice fields. Cyhalofop-butyl works by selectively inhibiting acetyl CoA carboxylase, an enzyme that is important for the metabolism of fatty acids.
(R)-2-(4-hydroxyphenoxy)propionic acid ((R)-HPOPA) is an essential intermediate for the production of chiral aryloxyphenoxypropionic acid-type herbicides such as clod inafop-propargyl, cyhalofop-butyl, fenoxaprop-p-ethyl, metam ifop, quizalofop-p-ethyl, and quizalofop-p-tefuryl. In general, there are three chemical methods for the preparation of (R)-HPOPA: (1) resolution of racemic HPOPA with alkaloids such as quinine, cinchonine, ephedrine, vauquline or chiral agents such as S-(?)-α-phenylethylamine, L-(+)-chloromethane, R-(+)-α-isopropyl-4-chlorobenzylamine and (2) asymmetric synthesis from L-lactic acids or L-alanine. However, these methods are not always useful for industrial applications because of expensive reagents, problems with enantiopurity of product and low yields. Regioselective hydroxylation of (R)-2-phenoxypropionic acid ((R)-POPA) by microbes is a highly feasible method for the production of (R)-HPOPA, which under mild conditions allows complete transformation of substrate into a single stereoisomeric product with a high yield and without byproduct formation[1-2].
[1] Hai-Feng Hu . “A rapid throughput assay for screening (R)-2-(4-hydroxyphenoxy)propionic acid producing microbes.” Journal of microbiological methods 158 (2019): Pages 44-51.
[2] Haiyan Zhou. “An efficient route towards R-2-phenoxypropionic acid synthesis for biotransformative production of R-2-(4-hydroxyphenoxy)propionic acid.” Chinese Journal of Chemical Engineering 32 (2021): Pages 315-323.
