Chiral and C2-symmetric seven-membered cycloalkanones 2--6 bearing 1,2-diphenylethane-1,2-diamine and cyclohexane-1,2-diamine backbones were synthesized and evaluated their asymmetry inductive behaviours in an asymmetric epoxidation of stilbene with oxone. Although the reaction of the ketones 2 and 3 of a 1,2-diphenylethane-1,2-diamine backbone gave stilbene oxide in trace to 31% yield, those o...

A chiral cyclophane–type macrocycle bearing two thiol groups has been prepared by chemical modification of S,S-(+)-tetrandrine. Cleavage of p-nitrophenyl acetate by deprotonated form of this macrocycle proceeds with a rate constant expected for a simple thiol anion of similar basicity, but the reactivity toward p-nitrophenyl esters of N-protected amino acids is one order of magnitude higher tha...

The capabilities of porcine pancreatic lipase (PPL), Candida antarctica lipase (CAL), and Candida rugosa lipase (CRL) were evaluated for enantioand/or regioselective acetylation/deacetylation of (±)-2,4-diacetoxyphenyl alkyl ketones, (±)-4-alkyl-3,4-dihydro3-hydroxyalkyl-2H-1,3-benzoxazines, and D-arabino and D-threo-polyhydroxyalkyltriazoles in organic solvents. PPL in tetrahydrofuran (THF) ex...

A novel approach based on efficient path-planning algorithms was applied to investigate the influence of substrate access on Burkholderia cepacia lipase enantioselectivity. The system studied was the transesterification of 2-substituted racemic acid derivatives catalysed by B. cepacia lipase. In silico data provided by this approach showed a fair qualitative agreement with experimental results,...

The role of the sugar moiety of glycopeptide antibiotics in chiral recognition was investigated with capillary electrophoresis. Two glycopeptide antibiotics, vancomycin and balhimycin, were employed as models since they possess the same aglycon and almost identical sugar moieties, however, with different attachment sites to the aglycon. The observed enantioselectivity of balhimycin for dansylat...

In this paper, the chiral surfactants bearing two long alkyl chains with hydroxyl groups at their terminals were synthesized and employed to encapsulate a catalytically efficient polyoxometalate through electrostatic interaction. The obtained chiral surfactant-encapsulated polyoxometalate complexes, in which a defined chiral microenvironment surrounds the inorganic cluster, were covalently immo...

Platinum nanoclusters modified with cinchonidine have been employed as 'quasi-homogeneous' catalysts for the hydrogenation of ethyl pyruvate and have demonstrated exceptional activities while the ee's of these systems are currently inferior to the traditional Pt/Al2O3 heterogeneous system. For the bulk systems it has been shown that the orientation of the modifier on the metal surface is a crit...

Background: Hydrolysis of 2-amino phenylpropionitrile by nitrilase is a fundamental biochemical reaction that produces chiral phenylalanine. For practical application of this biochemical reaction, researchers have attempted to improve enzyme enantioselectivity and the reaction rate. Results: The substrate concentration was increased from 100 to 200 mM without substrate inhibition because of the...

In the asymmetric addition of allyltrichlorosilane to benzaldehyde, polystyrenes with chiral phosphoramide substituents as Lewis base catalysts showed up to 2.4 times better catalytic activity and 1.4 times higher enantioselectivity than the corresponding low-molecular-weight analogues.

Organocatalysts for the asymmetric reduction of ketimines are presented that function well at low catalyst loadings providing chiral amines in good yield and enantioselectivity, the latter appearing to be independent of the ketimine substrate geometry.