Enhancing Enantioselectivity and Productivity of P450-Catalyzed Asymmetric Sulfoxidation with an Aqueous/Ionic Liquid Biphasic System

Abstract

Biocatalytic asymmetric sulfoxidation represents a green method to prepare the useful and valuable enantiopure sulfoxides, but this method sometimes suffers from unsatisfied enantioselectivity and low productivity due to substrate and product inhibitions. Here we developed an aqueous/ionic liquid (IL) biphasic system for simultaneously enhancing the enantioselectivity and productivity of P450 monooxygenase-catalyzed asymmetric sulfoxidations of sulfides 1, 3, 5, 7, and 9, as the first example of this kind for a biooxidation. Escherichia coli (P450pyrI83H-GDH) coexpressing P450pyrI83H monooxygenase and glucose dehydrogenase was engineered for the asymmetric sulfoxidations with cofactor recycling, giving higher R-enantioselectivity than any other known P450 monooxygenases and showing high specific activities. The inhibition to the reactions and the toxicity to the cells of the substrates and products were investigated and mostly avoided by using a KP buffer/[P 6,6,6,14 ][NTf 2 ] biphasic reaction system, in which the IL showed excellent biocompatibility to the cells and high solubility to the substrates and products. Sulfoxidations of 1, 3, 5, 7, and 9 with the resting E. coli cells in the biphasic system increased the product concentration from 9.4 to 20 mM for (R)-phenyl methyl sulfoxide 2, from 1.9 to 9.9 mM for (R)-4-fluorophenyl methyl sulfoxide 4, from 5.4 to 16 mM for (R)-ethyl phenyl sulfoxide 6, from 4.2 to 22 mM for (R)-methyl p-tolyl sulfoxide 8, and from 5.7 to 24 mM for (R)-methyl pmethoxyphenyl sulfoxide 10, respectively, and improved the product ee from 85 to 99% for (R)-2, from 80 to 98% for (R)-4, from 88 to 96% for (R)-6, from 35 to 62% for (R)-8, and from 53 to 67% for (R)-10, respectively. The enhancements in enantioselectivity are possibly caused by the low substrate concentrations in the aqueous phase of the biphasic system. Preparative sulfoxidations to produce the useful and valuable sulfoxides (R)-2, (R)-4, and (R)-6 in 99%, 98%, and 96% ee, respectively, were demonstrated.

Biocatalytical Asymmetric Sulfoxidation by Identifying Cytochrome P450 from Parvibaculum Lavamentivorans DS‐1

“…However, the yield reduced dramatically by increasing the substrate concentration (entry 4), suggesting that 1 a inhibits the activity of P450 PL2 ‐2. This substrate inhibition behavior has been found in other P450‐catalyzed sulfoxidation reactions, which can be remedied slightly by using aqueous/ionic liquid biphasic system . Excitingly, the yield of the compound 2 a was improved to 59 % with the enantioselectivity remaining unchanged when using ethanol as a cosolvent, which might attribute to the increase of the solubility of 1 a (entry 5).…”

“…The cytochrome P450 monooxygenases (P450s or CYPs) are versatile biocatalysts that ubiquitously exist in almost all living systems, and involved in a diverse range of oxidation reactions such as hydroxylation, epoxidation, sulfoxidation, oxidative phenolic coupling, N ‐ and O ‐dealkylation, carbon‐carbon bond cleavage and cyclopropanation . The bacterial P450s can be divided into ten classes according to their topologies .…”

One‐Pot Production of Natural 2‐Phenylethanol from L‐Phenylalanine via Cascade Biotransformations

“…Two‐phase extraction is a cost effective, easily scalable, and simple ISPR technique, and oleic acid, polypropylene glycol 1200, 1‐decanol, oleyl alcohol, and rapeseed oil were used for in‐situ product extraction in other biocatalytic systems to produce 2‐PE 6 . To select an appropriate non‐aqueous solvent for our two‐phase cascade biotransformation, seven non‐aqueous solvents, including ionic liquids (IL) and biodiesel, were examined for the biotransformation of L ‐Phe 1 to 2‐PE 6 with the resting cells of E. coli (RE). The partition coefficients (K) of L ‐Phe 1 , trans‐ cinnamic acid 2 , styrene 3 , (S) ‐styrene oxide 4 , phenylacetaldehyde 5 , and 2‐PE 6 in biphasic system were determined.…”

Palladium nanoparticles embedded in improved mesoporous silica: a pH‐triggered phase transfer catalyst for Sonogashira reaction

“…[11][12][13][14] More specifically, recent research indicates that template-containing mesoporous silica is an interesting composite for various applications. [24][25][26][27][28] However, while biphasic conditions facilitate separation of catalyst and product and catalyst reuse, multiple phases introduce kinetic barriers and mass transfer limitations. [21][22][23] It is even better that an extraction solvent can be avoided by developing biphasic catalytic protocols.…”