Regioselectivity esterification reactions

Regioselective esterification and acetylation reactions of lactose were described by Thelwall (1982). These selective reactions produced partially protected derivatives which were of value in the further modifica-... 

In addition to hydrolyzing carboxylic ester bonds, lipases can catalyze a variety of esterification reactions in non-aqueous media. Industrial applications of lipases have focused on their enantioselectivity, regioselectively and substrate... 

For the last few years, Kobayashi s and Gross s groups have been independently working on the synthesis of alditol-based polyesters by lipases as catalysts for selective polyol polymerizations. Lipases and proteases are well known as providing regioselectivity during esterification reactions at mild temperatures. In addition to this, the use of... 

In another study, Padovani showed that CALB-catalyzed modification of pendant ester groups of a polystyrene derivative provided a clear-cut regioselective transesterification reaction [152]. Of the pendant two ester groups available on the polymer backbone, only the ester group distant from the polymer backbone was involved in the lipase-catalyzed esterification reaction. The results suggested that formation of the acyl-enzyme intermediate is sterically not possible for the ester... 

Another advantageous feature of enzymes in an esterification reaction lies in their ability to distinguish a specific hydroxyl group of a complex polyalcohol like sugar derivatives. KUbanov et aL found that Bacillus subtilis protease (subtilirin) catalyzes the regioselective acylation disaccharides 16, as well as nucleosides and related compounds in N,N-dimethylformamide [40]. 

It is clear that the optimization of the reaction medium and the reaction conditions will be necessary to improve yield and the regioselectivity of these reactions. Nevertheless, the feasibility of enzymatic esterification reactions with polar substrates in near-anhydrous solvents opens a broad spectrum of possibilities of new enzymatic synthesis reactions. 

The esterification can also be carried out as a one-pot reaction without isolation of the azolide for example, an 80% yield of crocetin bis(/ -D-glucosyl ester) was obtained via the triazolide. 1953 Reactions of 8 -apo-/ -carotene-8 -oic acid with D-galactose or lactose were claimed to proceed also with a high degree of regioselectivity.11963... 

N. R. Pedersen, R. Wimmer, J. Emmersen, P. Degn, and L. H. Pedersen, Effect of fatty acid chain length on initial reaction rates and regioselectivity of lipase-catalysed esterification of disaccharides, Carbohydr. Res., 337 (2002) 1179-1184. 

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