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.

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 β- to α-selectivity.