819-97-6Relevant academic research and scientific papers
Enantioselective transesterification catalysis by nanosized serine protease subtilisin Carlsberg particles in tetrahydrofuran
Castillo, Betzaida,Delgado, Yamixa,Barletta, Gabriel,Griebenow, Kai
experimental part, p. 2175 - 2180 (2010/04/29)
Enzyme catalysis in organic solvents is a powerful tool for stereo-selective synthesis but the enantioselectivity is still hard to predict. To overcome this obstacle, we employed a nanoparticulate formulation of subtilisin Carlsberg (SC) and designed a series of 14 structurally related racemic alcohols. They were employed in the model transesterification reaction with vinyl butyrate and the enantioselectivities were determined. In general, short alcohol side chains led to low enantioselectivties, while larger and bulky side chains caused better discrimination of the enantiomers by the enzyme. With several bulky substrates high enantioselectivities with E>100 were obtained. Computational modeling highlighted that key to high enantioselectivity is the discrimination of the R and S substrates by the sole hydrophobic binding pocket based on their size and bulkiness. While bulky S enantiomer side chains could be accommodated within the binding pocket, bulky R enantiomer side chains could not. However, when also the S enantiomer side chain becomes too large and does not fit into the binding pocket anymore, enantioselectivity accordingly drops.
Structure-function correlation in lipase catalysed esterification reactions of short and medium carbon chain length alcohols and acids
Divakar, Soundar
, p. 1919 - 1922 (2007/10/03)
An attempt has been made to correlate the carbon chain lengths of acids and alcohols to the extent of esterification in the Rhizomucor miehei lipase catalyzed esterification reactions involving acids of carbon chain length C2-C5 and alcohols of carbon chain length C1-C8.
Carboxylic acids supported on silica: A smooth acylating agent for alcohols
Da Graca Nascimento, Maria,Zanotto, Sandra Patricia,Scremin, Marivania,Rezende, Marcos Caroli
, p. 2715 - 2721 (2007/10/03)
An alternative procedure for the esterification of alcohols by short-chain carboxylic acids supported on silica is presented.
Novel Template Effects of Distannoxane Catalysts in Highly Efficient Transesterification and Esterification
Otera, Junzo,Dan-oh, Nobushisa,Nozaki, Hitosi
, p. 5307 - 5311 (2007/10/02)
The transesterification of carboxylic esters and the esterification of carboxylic acids are effected under mild conditions under catalysis by 1,3-disubstituted tetraalkyldistannoxanes 1.Various functional groups remain unaffected and otherwise difficult to obtain esters are accessible.An ester bearing a tertiary butyl group in the carboxylic acid moiety remained unchanged in competition experiments with a less bulky ester, which undergoes transesterification quantitatively.The unique features of the reactions are attributable to the template effects of the dimeric structure of 1.The facility with which compounds 1 can be converted into alkoxystannoxanes 2 and the synergistic effect of the proximate tin atoms of 2 play key roles in permitting smooth reactions and high selectivity.Another notable feature of compounds 1 is their unusually high solubility in organic solvents, even though the compounds have a metaloxane core as a major skeletal part.The double-layered structure of 1, in which the inorganic moiety is surrounded by eight alkyl groups, permits esterification to be driven to completion simply by heating a mixture of the carboxylic acid and the alcohol.The distannoxane-catalyzed esterification is irreversible, and thus, no hydrolysis of the product esters occurs when compounds 1 are used as catalysts.
CATALYSED LIQUID PHASE OXIDATION OF ACETALS BY MOLECULAR OXYGEN
Vcelak, Jaroslav,Klimova, Miroslava,Chvalovsky, Vaclav
, p. 847 - 866 (2007/10/02)
Nine different acetals have been oxidized in the presence of Co(OOCCH3)2*4H2O under isobaric conditions (0.1 - 0.2 MPa O2) while following the uptake of molecular oxygen.The reactivity of acetals was expressed by the rate constants of the autocatalytic model of oxidation.The main product of the oxidation are alcohols, esters and acids.The distribution of products and the total reactivity of acetals are controlled by the structure of both parts of acetal molecule.The dominant effects of the course of the reaction exerts the type of carbon atoms on which radicals are formed.The oxidation is accompanied by consecutive and co-oxidation reactions, by deactivation of the catalysts and by decarbonylation of intermediate products.The effect of oxygen pressure is reported and the more detailed radical mechanism of the oxidation is proposed.
Preparative Production of Optically Active Esters and Alcohols Using Esterase-Catalyzed Stereospecific Transesterification in Organic Media
Cambou, Bernard,Klibanov, Alexander M.
, p. 2687 - 2692 (2007/10/02)
A novel enzymatic approach to the production of optically active alcohols and esters from racemates is developed.It involves the use of esterase catalyzed transesterifications carried out in biphasic aqueous-organic mixtures.Water-insoluble substrates constitute the organic phase, while the enzyme is located in the aqueous phase.Since the fraction of the latter phase can be made very low, such an arrangement solves the problem of both the competition of an alcohol (the nucleophile) with water in the enzymatic reaction and poor solubility of most organic esters and alcohols in water.By use of porous supports (Sepharose or Chromosorb) filled with aqueous solutions of hog liver carboxyl esterase as a stereoselective catalyst and methyl propionate as a matrix ester, the following optically active alcohols and their propionic esters were produced on a preparative scale: 3-methoxy-1-butanol, 3-methyl-1-pentanol, 3,7-dimethyl-1-octanol, and β-citronellol.To overcome a rather narrow substrate specificity of hog liver carboxyl esterase, a nonspecific lipase from yeast (Candida cylindracea) also was employed as a stereoselective transesterification catalyst.Using an aqueous solution of this enzyme confined to the pores of Chromosorb and tributyrin as a matrix ester, we have prepared gram amounts of the following optically active alcohols and their butyric esters: 2-butanol, sec-phenethyl alcohol, 2-octanol, 1-chloro-2-propanol and 2,3-dichloro-1-propanol (subsequently nonenzymatically converted to optically active propylene oxide and epichlorohydrin, respectively), 6-methyl-5-hepten-2-ol, and 1,2-butanediol.
