Phthaloyl chitosan

Recent progress of basic and application studies in chitin chemistry was reviewed by Kurita (2001) with emphasis on the controlled modification reactions for the preparation of chitin derivatives. The reactions discussed include hydrolysis of main chain, deacetylation, acylation, M-phthaloylation, tosylation, alkylation, Schiff base formation, reductive alkylation, 0-carboxymethylation, N-carboxyalkylation, silylation, and graft copolymerization. For conducting modification reactions in a facile and controlled manner, some soluble chitin derivatives are convenient. Among soluble precursors, N-phthaloyl chitosan is particularly useful and made possible a series of regioselective and quantitative substitutions that was otherwise difficult. One of the important achievements based on this organosoluble precursor is the synthesis of nonnatural branched polysaccharides that have sugar branches at a specific site of the linear chitin or chitosan backbone [89]. 

Opanasopit P, Ngawhirunpat T et al (2007) Camptothecin-incorporating N-phthaloyl-chitosan-g-mPEG self-assembly micellar system effect of degree of deacetylation. Colloids Surf B 60 117-124... 

Fully deacetylated chitosan has been treated with phthalic anhydride in N,N-dimethylformamide to give N-phthaloyl-chitosan that resulted soluble in polar organic solvents [120]. The C-6 hydroxyl groups of N-phtaloyl-chitosan were tritylated (triphenyl methylated) to give a derivative useful for substitution at C-3. Acetylation followed by detritylation gave another derivative easily convertable to the trimethylsilylated derivative (Figure 8). 

Liu L, Wang YS et al (2005) Preparation of chitosan-g-polycaprolactone copolymers through ring-opening polymerization of epsilon-caprolactone onto phthaloyl-protected chitosan. Biopolymers 78 163-170... 

The 1,2-0-orthoesters derivatives of D-mannose and D-galactose were used as glycosyl donors to incorporate a-mannoside and P-galactoside branches at C-6 of chitin and its N-deacetylated form chitosan [135] employing a N-phthaloyl 6-O-tri-methylsilylated chitosan derivative as an acceptor. 

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