Bo-Kai Liu

Enzymatic Promiscuity for Organic Synthesis and Cascade Process

Enzymatic promiscuity, namely the possibility that one active site of an enzyme can catalyze several different chemical transformations, has been an important research field and valuable synthesis tool for protein engineering and synthetic chemistry. This review will focus on promiscuous enzyme-mediated reactions that are useful in organic synthesis. Examples include promiscuous hydrolysis reactions, Michael addition, Markovnikov addition, aldol condensation, Henry reaction, Mannich reaction, Epoxidation reaction, Baeyer-Villiger oxidation, radical polymerization and tandem reactions catalyzed by natural enzymes or engineered enzymes with existing or induced catalytic promiscuity. Among these examples, many enzymes from different family have been verified to be able to catalyze the same type of reaction through distinct mechanism. Many complex compounds or important intermediates can be synthesized using promiscuous enzymes or through novel synthesis pathways. These examples support the enormous potential of enzymatic promiscuity in synthetic chemistry.

Promiscuous zinc-dependent acylase-mediated carbon–carbon bond formation in organic media

A zinc-dependent acylase, D-aminoacylase from Escherichia. Coli, displays a promiscuous activity to catalyze the carbon-carbon bond formation reaction of 1,3-dicarbonyl compounds to methyl vinyl ketone in organic media.

Hydrolase-catalyzed fast Henry reaction of nitroalkanes and aldehydes in organic media

Nitroalkanes underwent fast additions to a variety of structurally diverse aldehydes under the catalysis of d-aminoacylase in DMSO. The influences of reaction conditions including solvents, temperature, enzyme concentration and molar ratio of substrates were systematically investigated. Seventeen products were obtained in short time with moderate to high yields. It is the first report on hydrolase-catalyzed fast Henry reaction in organic solvent.

A green protocol for synthesis of benzo-fused N,S-, N,O- and N,N-heterocycles in water

A fast and efficient protocol which is associated with readily available starting materials, mild conditions, excellent yields, and a broad range of the products in synthetic chemistry, was established for synthesis of quinoxaline, benzoxazine, and benzothiazine derivatives in water under catalyst-free conditions.

N-Methylimidazole significantly improves lipase-catalysed acylation of ribavirin

N-methylimidazole, a molecular solvent, but also, in cationic form, a component of 1-alkyl-3-methylimidazolium ([C(n)MIM]+) ionic liquids, showed promise as an additive in accelerating remarkably transesterification catalyzed by lipase acrylic resin from Candida antarctica (CAL-B).

A novel control of enzymatic enantioselectivity through the racemic temperature influenced by reaction media

The influence of reaction media on the racemic temperature (T(r)) in the lipase-catalyzed resolution of ketoprofen vinyl ester was investigated. An effective approach to the control of the enzymatic enantioselectivity and the prediction of the increasing tendency was developed based on the T(r) influenced by reaction media. The T(r) for the resolution catalyzed by Candida rugosa lipase (CRL) was found at 29 °C in aqueous and S-ketoprofen was obtained predominantly at 40 °C. However, CRL showed R-selectivity at 40 °C in diisopropyl ether because the T(r) was changed to 56 °C. CRL, lipase from AYS Amano(®) and Mucor javanicus lipase were further applied for the investigation of the enzymatic enantioselectivity in dioxane, DIPE, isooctane and their mixed media with water. The effects of the reaction medium on T(r) could be related to the solvent hydrophobicity, the lipase conformational flexibility and the interaction between the enantiomers and the lipase.

Enzymatic synthesis of optical pure β-nitroalcohols by combining D-aminoacylase-catalyzed nitroaldol reaction and immobilized lipase PS-catalyzed kinetic resolution

An enzymatic method which combines D-aminoacylase catalyzed nitroaldol reaction and lipase PS-IM catalyzed acyl resolution reaction was constructed to obtain optically pure β-nitroalcohols in organic media under mild conditions. A series of β-nitroalcohols were synthesized and then resolved, with excellent ee values (>95%) and yields mostly, giving enantiomerically pure acetate and alcohol of the opposite configuration simultaneously.

Regioselective enzymatic acylation of ribavirin to give potential multifunctional derivatives

Lipase-catalyzed synthesis of potential multifunctional ribavirin derivatives was performed in acetone. Divinyl dicarboxylates with different chain lengths (C4, C6, C9, C10) were used as acyl donors and the reactions were catalyzed by lipase immobilized on acrylic resin from Candida antarctica (CAL-B). Ribavirin was regioselectivly acylated at the primary hydroxyl groups and the corresponding vinyl esters (C4, C6, C9, C10) were prepared in respective yields of 48%, 65%, 54%, 55%.

Modulating the synthetase activity of penicillin G acylase in organic media by addition of N-methylimidazole: using vinyl acetate as activated acyl donor.

This paper reported the modulation of enzyme activity by organic small molecule. The esterification activity of Penicillin G acylase (PGA) was improved more than 70-fold by the addition of 10% N-methylimidazole. Some control experiments have been designed to demonstrate the catalytic specificity of PGA. The structure and the amount of additive were optimized to improve the product yield. The influence of N-methylimidazole on the PGA conformation was investigated by FTIR and autodock simulation. Seven substrates were used to evaluate the effect of structure on the PGA-catalyzed transesterification. A series of products were successfully synthesized with the yield ranged from 56% to 84% and PGA showed specific recognition on the substrate with phenyl group in the presence of 10% N-methylimidazole.

Facile synthesis of novel mutual derivatives of nucleosides and pyrimidines by regioselectively chemo-enzymatic protocol

We established a facile regioselectively chemo-enzymatic synthesis procedure for the preparation of mutual derivatives of nucleosides and pyrimidines by sequential Markovnikov addition and acylation. Firstly, pyrimidine derivatives containing vinyl ester group were synthesized from pyrimidines and divinyl esters through Markovnikov addition catalyzed by K(2)CO(3) in DMSO at 80 degrees C, and the yields were ranged from 50% to 87%. Then regioselective acylation of ribavirin and cytarabine with pyrimidine vinyl ester was catalyzed by CAL-B (immobilized lipase from Candida antarctica) in anhydrous acetone. Reaction conditions of enzymatic acylation including enzyme resource and solvents were optimized. A series of mutual derivatives of nucleosides and pyrimidines were synthesized successfully and characterized with NMR, IR, and HRMS. This chemo-enzymatic protocol involving sequential Markovnikov addition and acylation provided a novel way of synthesizing complicated functional compounds regioselectively which was hard to be achieved either by chemical or by enzymatic methods.