Green Synthesis and Catalysis最新文献

Chiral methyl mandelates are useful synthons in organic transformation and pharmaceutical synthesis. Green synthesis of these valuable compounds by direct C–H activating oxidative hydroxylation has attracted keen interest. Described herein is achieving the stereoselective and efficient bio-hydroxylation of methyl 2-phenylacetates to the chiral methyl mandelates by directed evolution of the cytochrome P450DA hydroxylase. In the present study, a new colorimetric high-throughput screening assay was successfully developed based on a dual-enzyme cascade for the engineering of the P450DA's hydroxylation activity. Several beneficial variants with enhanced bio-hydroxylation activity were created by combining random mutagenesis and site-saturated/directed mutagenesis strategies. Whole-cell bio-hydroxylation of various methyl 2-phenylacetates using the best septuplet-mutant P450DA-11 yielded the corresponding chiral methyl mandelates in up to 92% isolated yields and >99% ee.

Asymmetric reduction of the conjugated CC bonds by the old yellow enzymes (OYEs) presents a promising field in the synthesis of chiral chemicals. Nevertheless, few natural OYEs have been applied in large-scale applications due to the requirement of costly NADPH and low operational stability. Herein, a stable and efficient fusion of YqjM from Bacillus subtilis and glucose dehydrogenase (GDH) from Bacillus megaterium was constructed to stereoselectively reduce the conjugated CC bonds in a self-sufficient continuous process. The effects of the enzyme order and different linkers on the fusions were investigated by structural analysis and all-atom molecular dynamics simulation. The best fusion YqjM_G_GDH gave 98% conversion of 100 ​mmol/L 2-methylcyclopentenone with an excellent ee value (>99%) in 3 ​h, while the mixture of individual enzymes only obtained 68% conversion after more than 8 ​h. The improved substrate conversion of YqjM_G_GDH fusion was probably attributed to the increased flexibility of each fused enzyme and the shortening of the diffusion distance of NADPH regenerated. A one-pot process was designed to purify and immobilize the fusion on the Ni²⁺-nitrilotriacetic acid functionalized magnetic mesoporous silica nanoflowers. The resulting immobilized biocatalyst not only catalyzed the asymmetric reduction of various α,β-unsaturated ketones (20 ​mmol/L) continuously with only 50 ​μmol/L NADP⁺ to initiate the whole process, but also retained more than 82% of the initial activity after seven cycles, serving as a good candidate for the industrial applications.

Core-shell structured magnetic wrinkled organosilica-based metal-enzyme integrated catalysts were synthesized, and their catalytic performances were studied in the chemoenzymatic dynamic kinetic resolution of chiral amines in an organic solvent, as well as in the chemoenzymatic synthesis of chiral alcohols in water. Structure-performance studies revealed the important influence of their tunable structure and composition on the optimization of activity, stability, and recyclability in chemoenzymatic catalysis.

Heterogeneous asymmetric catalysis is an important strategy for the industrial production of chiral compounds. Herein, we reported a polymer-bound Xu-Phos-derived palladium catalyst that shows good performance in heterogeneous asymmetric reductive Heck reaction of allyl aryl ethers. This heterogeneous catalyst was easily prepared by efficient immobilization of the sulfonamide phosphine ligand (Xu-Phos) in the cross-linked polystyrene via copolymerization, and exhibits similar catalytic activity and enantioselectivity to that of the homogeneous catalyst. Moreover, the heterogeneous catalyst system is proved to be easily recovered and reused several times without losing catalytic activity obviously.

Non-covalent interactions are of significance in supramolecular chemistry and biochemistry, while synthetic procedures driven by these weak interactions remain challenging and rare. Inspired by the lone pair-π interaction presence in the Z-DNA structure, a light-induced regioselective sulfonation of ethers taking advantage of the lone pair-π interaction between the oxygen of ethers and sulfonyl chlorides has been disclosed. Moreover, this strategy is also applicable to the sulfonation of aniline derivatives. Features of the methods include readily accessible starting materials, high atom-economy, green and photocatalyst-free conditions and broad functional group tolerance. Mechanism studies suggest that the lone pair-π interaction plays an important role to initiate the transformation.