Hydrolysis of glycosides with microgel catalysts.

A dormant macromolecular catalyst was prepared by polymerization of an aqueous styrene-butyl acrylate miniemulsion in the presence of a new polymerizable pentadentate ligand. The catalyst was activated by binding Cu(II) ions to the ligand site and then explored for its ability to hydrolyze glycosidic bonds in alkaline solution. The performance was correlated to the catalytic activity shown by low molecular weight analogs. A turnover rate of up to 43 × 10(-4) min(-1) was previously observed for cleavage of the glycosidic bond in selected p-nitrophenylglycosides with a binuclear, low molecular weight catalyst; by contrast, the same reaction is more than 1 order of magnitude faster and has a turnover rate of up to 380 × 10(-4) min(-1) when using the prepared macromolecular catalyst. The catalyzed hydrolysis is about 10(5)-fold accelerated over the uncatalyzed background reaction under the provided conditions, while a significant discrimination of the α- and ß-glycosidic bond or of the galacto- and gluco-configuration in the sugar moiety in the glycoside substrates is not observed.

Multi gram-scale synthesis of galactothionolactam and its transformation into a galactonoamidine.

We recently proposed to conduct selective glycosylation reactions after in situ activation of a glycosyl donor promoted by a transition metal complex immobilized in a macromolecular matrix. In order to develop this catalytic entity, a feasible multi gram-scale synthesis for 2,3,4,6-tetra-O-benzyl-d-galactothionolactam, its transformation into galactonoamidines with aromatic aglycon, and subsequent debenzylation conditions were developed. The potential for epimerization reactions at C-2 of the glycosidic ring during the transformations from the 2,3,4,6-tetra-O-benzyl-d-galactonolactam into the N-benzyl-2,3,4,6-tetra-O-benzyl-d-galactonoamidines via the 2,3,4,6-tetra-O-benzyl-d-galactothionolactam are discussed and additionally characterized by using density functional theory calculations.

Versatile syntheses of mono- or bis-allylhalothiol-carbonates of some alditol or sugar derivatives via cyclic thionocarbonates as intermediates.

We describe herein an extension of the halogenation of 1,2 or 1,3-diols via a cyclic thionocarbonate functionality by reaction with an allyl halide instead of methyl iodide, which is usually used. This investigation was successfully carried out under both conventional heating and microwave solvent-free conditions with some alditol, thioanhydroalditol, and aldose derivatives.