Mapping the substrate selectivity of new hydrolases using colorimetric screening: lipases from Bacillus thermocatenulatus and Ophiostoma piliferum, esterases from Pseudomonas fluorescens and Streptomyces diastatochromogenes
作者:Andrew Man Fai Liu、Neil A Somers、Romas J Kazlauskas、Terry S Brush、Frank Zocher、Markus M Enzelberger、Uwe T Bornscheuer、Geoff P Horsman、Alessandra Mezzetti、Claudia Schmidt-Dannert、Rolf D Schmid
DOI:10.1016/s0957-4166(01)00072-6
日期:2001.3
screened a general library of 29 substrates and a chiral library of 23 pairs of enantiomers. All four hydrolases catalysed the hydrolysis of unnatural substrates, but the two lipases accepted a broader range of substrates than the two esterases. As expected, the two lipases favoured more hydrophobic substrates, while the two esterases showed a preference for smaller substrates. Several moderately enantioselective
Many are called but few are chosen: A nonheme iron complex catalyzes the oxidation of alkyl CHbonds by using H2O2 as the oxidant, showing an enhanced selectivity for secondary over tertiary CHbonds (see scheme).
Lewis acid catalyzed acylation reactions: scope and limitations
作者:Kusum L Chandra、P Saravanan、Rajesh K Singh、Vinod K Singh
DOI:10.1016/s0040-4020(01)01229-7
日期:2002.2
Acylation of alcohols, thiols, and sugars were studied with a variety of Lewis acids, and it was found that Cu- and Sn(OTf)2 are very efficient in catalyzing the reaction under mild conditions. Among these two catalysts, Cu(OTf)2 was preferred because of its lower cost and relatively higher yield of the acylated product. The reaction was studied in several solvents, but CH2Cl2 was preferred. It was
Part 148 in the Series “Studies on Novel Synthetic Methodologies:” Selective Acetylation of Alcohols, Phenols and Amines and Selective Deprotection of Aromatic Acetates using Silica-Supported Phosphomolybdic Acid
efficient catalyst for the selective acetylation of alcohols, phenols and amines in the absence of any solvent and also for the chemoselective deprotection of aromatic acetates under very mild conditions. This method has been used for the protection of the hydroxy groups as well as for the deprotection of the acetates of several naturally occurring bioactive phenolic compounds. The catalyst can be easily
Cu(OTf)2 was found to be an efficient catalyst in the acylation reaction of alcohols, phenols, amines and thiols with acetic anhydride in CH2Cl2 or acetic acid. A catalytic cycle has been proposed for the acylation reaction.