Synthesis and study of the glycosyl-donor properties of 2-(2,2,2-trichloroethoxy)-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-galactopyrano)-[2,1-d]-2-oxazoline.

A synthesis of 2-(2,2,2-trichloroethoxy)-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-galactopyrano)-[2,1-d]-2-oxazoline - a previously unknown 2-alkoxy glyco-[2,1-d]-2-oxazoline derivative with d-galacto configuration was carried out. Glycosylating activity of the obtained galactooxazoline has been studied and it has been shown that in the presence of a weak protic acid, such as sym-collidinium triflate, this substance exhibits properties of a reactive and 1,2-trans-stereoselective glycosyl donor. The homopolymerization reaction of oxazoline derivatives of sugars has been found to proceed under the same conditions, leading to the formation of pseudo-oligosaccharide products. It has been found that this undesirable side reaction could be suppressed by changing the acid catalyst concentration, resulting in the development of efficient methods for the synthesis of glycoside and oligosaccharide derivatives of ß-d-galactosamine using the synthesized 2-(2,2,2-trichloroethoxy)-2-oxazoline glycosyl donor under very mild conditions.

New methods for the synthesis of 2-(2,2,2-trichloroethoxy)-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline and its use for stereo-, chemo- and regioselective glycosylation.

New methods for the synthesis of the title oxazoline 2 from the corresponding 2-deoxy-2-(2,2,2- trichloroethoxycarbonylamino)glucosyl bromide were developed. The target 2-(2,2,2-trichloroethoxy) gluco-[2,1-d]-2-oxazoline 2 can be synthesized under conditions of halide ion catalysis, using triethylamine as a base. The synthesized 2-(2,2,2-trichloroethoxy)-2-oxazoline glycosyl donor was used for stereo-, regio-, and chemoselective glycosylation reactions under extremely mild conditions. The undesirable side reaction of intermolecular aglycone transfer between an ethyl thioglycoside glycosyl acceptor and the 2-(2,2,2-trichloroethoxy)-2-oxazoline glycosyl donor occurred to a relatively small extent. Regio-, and chemoselectivity of the disaccharide synthesis with the oxazoline glycosyl donor depended on the reaction conditions.

The study of the acid-catalyzed reaction between 2-methyl and 2-(2,2,2-trichloroethoxy) gluco-[2,1-d]-2-oxazolines. Synthesis of macrocyclic pseudo-tetrasaccharide derivative of d-glucosamine.

The formation of macrocyclic pseudo-tetrasaccharide derivative of d-glucosamine as a result of the acid-catalyzed reaction between 2-methyl- and 2-(2,2,2-trichloroethoxy)-substituted oxazoline derivatives of sugars was discovered. The structure of the obtained product was determined using NMR spectroscopy and mass spectrometry. An explanation of the obtained results based on the mechanism of the reaction of electrophilic polymerization of 2-substituted glyco-[2,1-d]-2-oxazolines and the principle of hard and soft acids and bases (HSAB) was proposed.

Synthesis of some 2-alkoxy glyco-[2,1-d]-2-oxazolines and evaluation of their glycosylation reactivity.

The synthesis of the title compounds using intramolecular nucleophilic substitution reactions in the molecules of the corresponding 2-alkoxycarbonylamino-2-deoxy glucosyl halides was studied. It was found that in contrast to the 2-alkyl (aryl) glyco-[2,1-d]-2-oxazolines, the synthesis of the target 2-alkoxy glyco-[2,1-d]-2-oxazolines was possible only in highly basic media. The synthesized 2-alkoxy oxazoline derivatives turned out to be active glycosyl donors and were used for stereoselective 1,2-trans glycosylation reactions catalyzed by weak protic acid under very mild conditions, thus preventing anomerization and other side reactions. As a result of this glycosylation, the glycoside and oligosaccharide derivatives containing urethane N-protecting groups were formed.

Synthesis of 1,2-cis- and 1,2-trans-glycosides of 2-acetamido-4,6-O-benzylidene-2-deoxy-D-glucopyranose by anomeric O-alkylation.

The reaction of a partially protected 1-hydroxy derivative of N-acetyl-D-glucosamine with benzyl bromide under conditions of anomeric O-alkylation was studied. It was found that the stereoselectivity of the reaction depended on the nature of the alkali metal cation constituent of a transient ion pair. The substitution of the Li(+) cation for K(+) or complexation with a crown ether allowed the steric outcome to be shifted from ß- to α-selectivity.