Enantioselective trans-Dihydroxylation of Aryl Olefins by Cascade Biocatalysis with Recombinant Escherichia coli Coexpressing Monooxygenase and Epoxide Hydrolase

Abstract

Cascade biocatalysis via intracellular epoxidation and hydrolysis was developed as a green and efficient method for enantioselective dihydroxylation of aryl olefins to prepare chiral vicinal diols in high ee and high yield. Escherichia coli (SSP1) coexpressing styrene monooxygenase (SMO) and epoxide hydrolase SpEH was developed as a simple and efficient biocatalyst for S-enantioselective dihydroxylation of terminal aryl olefins 1a−15a to give (S)-vicinal diols 1c−15c in high ee (97.5−98.6% for 10 diols; 92.2−93.9% for 3 diols) and high yield (91−99% for 6 diols; 86−88% for 2 diols; 67% for 3 diols). Combining SMO and epoxide hydrolase StEH showing complementary regioselectivity to SpEH as a biocatalyst for the cascade biocatalysis gave rise to R-enantioselective dihydroxylation of aryl olefins, being the first example of this kind of reversing the overall enantioselectivity of cascade biocatalysis. E. coli (SST1) coexpressing SMO and StEH was also engineered as a green and efficient biocatalyst for R-dihydroxylation of terminal aryl olefins 1a−15a to give (R)-vicinal diols 1c−15c in high ee (94.2−98.2% for 7 diols; 84.2−89.9% for 6 diols) and high yield (90−99% for 6 diols; 85−89% for 5 diols; 65% for 1 diol). E. coli (SSP1) and E. coli (SST1) catalyzed the trans-dihydroxylation of trans-aryl olefin 16a and cis-aryl olefin 17a with excellent and complementary stereoselectivity, giving each of the four stereoisomers of 1-phenyl-1,2-propanediol 16c in high ee and de, respectively. Both strains catalyzed the trans-dihydroxylation of aryl cyclic olefins 18a and 19a to afford the same trans-cyclic diols (1R,2R)-18c and (1R,2R)-19c, respectively, in excellent ee and de. This type of cascade biocatalysis provides a tool that is complementary to Sharpless dihydroxylation, accepting cis-alkene and offering enantioselective trans-dihydroxylation.

Biocatalytic Epoxidation for Green Synthesis

“…By removing epoxide quickly from the aqueous phase through the subsequent hydrolysis, any inhibiting effects are reduced, and the conversion of styrene was accelerated by a factor of 2 (Scheme 13.10a). The strategy was further developed into a cascade biocatalysis via intracellular epoxidation and hydrolysis using recombinant E. coli coexpressing SMO and SpEH with expanded substrate spectrum [107]. In addition, the stereocomplementary process was also established by applying an epoxide hydrolase (StEH) with opposite regioselectivity, resulting in the inversion of configuration to produce (R)-vicinal diols (Scheme 13.10b) [107].…”

“…The strategy was further developed into a cascade biocatalysis via intracellular epoxidation and hydrolysis using recombinant E. coli coexpressing SMO and SpEH with expanded substrate spectrum [107]. In addition, the stereocomplementary process was also established by applying an epoxide hydrolase (StEH) with opposite regioselectivity, resulting in the inversion of configuration to produce (R)-vicinal diols (Scheme 13.10b) [107]. Besides SMOs, recombinant E. coli expressing the xylene monooxygenase from P. putida mt-2, which typically oxidizes toluene and xylenes to the corresponding benzyl alcohol derivatives, can as well catalyze the epoxidation of styrene into (S)-styrene oxide [49,108].…”

A Chimeric Styrene Monooxygenase with Increased Efficiency in Asymmetric Biocatalytic Epoxidation

“…In these preliminary experiments, we determined the level of conversion for the epoxidation of styrene ( 1 a ) after a specific reaction time by lyophilised E. coli whole cells overexpressing Fus‐SMO in a biphasic system (aqueous buffer/ n ‐decane, Table S2 in the Supporting Information). As reported in the literature, the organic phase acts as a styrene reservoir and reduces the molecular toxicity of the product styrene oxide. Interestingly, the quantity and solubility of the expressed Fus‐SMO into the cells did not seem to correlate with a particular pigmentation of the host organism (Figures S2 and S3), whereas a difference in the level of conversion was observed only in one case for colony 2 (Table S2).…”

Epoxide Hydrolases and their Application in Organic Synthesis

“…HXN-200 or S. tuberosum [166]. The two E. coli strains, which were named SSP1 and SST1, were first tested as resting cells for the biotrans formation of 15 variously substituted styrene derivatives and styrene itself ( (1 : 1) phosphate buffer/n-hexadecane reaction medium with 10 g cdw/l of either the SSP1 or SST1 biomass.…”