Chemistry Modifications Of Natural Amino Polysaccharide Chitin

Chitin is widely distributed in nature. It is an important amino polysaccharide having acetamide groups or amino groups at the C-2 positions. The presence of amino groups in chitin is highly advantageous for providing distinctive biological functions and for conducting modification reactions. It' s a specialty biopolymer having specific properties including biodegradability, biocompatibility and bioactivity. This article reviewed the fundamental aspects of chitin and recent progress regarding some typical modifications including main chain hydrolysis, acylation, phthaloylation, tosylation , alkylation, Schiff base formation, 0-carboxymethylation , N'-carboxymethylation .Our emphasis is placed on the chemistry modifications to prepare chitin derivatives having advanced functions.(1) Traditional acylation is usually attained under rather severe conditions and the reactions proceed rather sluggishly; for example, acylation of chitin derivatives was achieved with carboxylic acid anhydrides or acyl chlorides. And all these methods have no selectivity. They can proceed at the free amino groups and the hydroxyl groups at the same time. It' s difficult to prepare chitin derivatives with well-defined structures.We find diacyl disulfides are good acylation reagents that can be synthesized easily. It only react with amino. Bis(benzoyl) disulfide react with ethylamine or dodecylamine in mild conditions, N-ethy'J benzamide and N-dodecyl benzamide attained with high yields. Due to the limited solubility of chitin derivatives, we didn' t find a common solventsuitable for both chitin and chitin derivatives. Our try to acylate chitin derivatives through this way is failed.(2)The full N-phthaloylated chitosan was prepared by treating achitosan suspension in DMF with excess phthlic anhydride at 120-130'C.We use the full N-phthaloylated chitosan as starting material , react witha -bromo-hexanoyl chloride, a -bromo-hexanoylation proceedregioselectively at C6-OH in homogeneous solutions in organic solvents.6-0- a -bromo-hexanoyl N-phthaloylated chitosan is a usefull macroinitiator for atom transfer radical polymer izat i on (ATRP) .(3)In the course of preparation of mercapto-chitin, we achieved progress in photobromination of selected organic compounds in two-phase mixture .A two-phase mixture (aromatic compounds and water) under visible light at room temperature provides a simple, convenient and efficient method for a benzylic-methyl bromination of many benzoic acids and benzoates. A high atomic yield for bromine atoms is attained.It is a big contribution to bromination methodology as well.