| Abstract
| - Regioselective introduction of α-mannoside branches at C-6 of chitin and chitosan has beenaccomplished by a series of regioselective modification reactions starting from N-phthaloyl-chitosan as akey precursor. Glycosylation of the derived acceptor with reactive groups only at C-6 with an ortho esterof d-mannose proceeded smoothly in dichloromethane in the presence of trimethylsilyl trifluoromethanesulfonate, and the degree of branching was up to 0.6. Full deprotection gave chitosans with α-mannosidebranches, which were subsequently transformed into the corresponding branched chitins by N-acetylation.The resulting branched polysaccharides showed a remarkable solubility in neutral water in sharp contrastto the insoluble linear chitin and chitosan. Concanavalin A exhibited a specific affinity for these products,which was ascribable to the presence of α-mannoside groups. Though nonnatural, the branched chitinswere susceptible to lysozyme, and the enzymatic degradation was heavily dependent on the extent ofbranching. Furthermore, the branched chitosan exhibited considerable antimicrobial activity.
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