Lipases aided esterification of (2,2-dimethyl-1,3-dioxolan-4-yl)methanol
Racemic solketal (2,2-Dimethyl-1,3-dioxolan-4-yl)methanol 1, was treated with carboxylic acids of varying chain length or their vinyl esters in the presence of different lipases. The esterification reaction was carried out in n-hexane or diisopropyl ether as a solvent. The yield of the solketal esters and their enantiopurity were satisfactory, as indicated by gas chromatography using chiral column. Lipases from Rhizopus oryzae and Pseudomonas fluorescence gave the best enantiomeric excess (ee) when the solketal was treated with vinyl butyrate in a solution of diisopropyl ether at room temperature.
Zniszczol, Aurelia,Walczak, Krzysztof Z.
p. 6 - 12
(2014/03/21)
Enhanced enantioselectivity of Bacillus coagulans in the hydrolysis of 1,2-O-isopropylidene glycerol esters by thermal knock-out of undesired enzymes
The enantioselective hydrolysis of different (RS)-1,2-O-isopropylidene glycerol esters has been achieved with whole cells of Bacillus coagulans NCIMB 9365 furnishing the (S)-alcohol as the major enantiomer. The reaction is catalysed by a thermostable cell-bound carboxylesterase and improvement of the enantioselectivity has been achieved by heat treatment of the whole cells, which causes the knock-outs a non-enantioselective competing enzyme. Thermally-treated cells hydrolysed (RS)-1,2-O-isopropylidene glycerol esters with high enantioselectivity, the highest enantiomeric ratio (80-100) being observed for the benzoate. The biocatalyst displayed good stability and could be re-used after filtration for 12 cycles before showing significant loss of activity; repeated biotransformation batches allowed the recovery of 9.55 g/L of enantiomerically pure (S)-isopropylideneglycerol benzoate starting from 24.0 g/L of the racemic mixture.
Romano, Diego,Falcioni, Francesco,Mora, Diego,Molinari, Francesco,Buthe, Andreas,Ansorge-Schumacher, Marion
p. 841 - 845
(2007/10/03)
Application of pig liver esterase catalyzed transesterification in organic media to the kinetic resolution of glycerol derivatives
The PLE/MPEG catalyzed transesterification of the glycerol ketals rac-1a and rac-1d-f with vinyl propionate in toluene proceeded with good selectivities (E=24-34) and gave the enantiomerically enriched S-alcohols 1a and 1d-f, and the S-esters 2a and 2d-f. High selectivities (E=99 and E≥200) were observed in the transesterification of the glycerol ether rac-3 and its desoxy analog rac-5, both having a secondary hydroxy group, with PLE/MPEG. In transesterifications in organic media PLE exhibited a much higher enantioselectivity than in hydrolysis in water.
Jungen, Manfred,Gais, Hans-Joachim
p. 3747 - 3758
(2007/10/03)
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