Alkyl deacetylated chitin

Sashiwa, H. and Shigemasa, Y. 1999. Chemical modification of chitin and chitosan. 2 Preparation and water soluble property of N-acylated or N-alkylated partially deacetylated chitins. Carbohydr. Polym. 39 127-138. 

Chemical. A large number of chitin and chitosan derivatives have been synthesized through modification of the primary (C-6) and secondary (C-3) hydroxyl groups present on each repeat imit, including amine (C-2) functionality existing on deacetylated imits (31). Reactions typical of hydroxyl and amine groups (such as acylations with acid chlorides and anhydrides) including urethane and urea formation respectively, are feasible with isocyanates. The primary amine can be quatemized by alkyl iodides or converted to an imine with a variety of aldehydes and ketones that can subsequently be reduced to an N-alkylated derivative. Chitin and chitosan are reactive with a variety of alkyl chlorides after treatment with concentrated NaOH. Important derivatives such as carboxymethylated chitin and chitosan are commonly produced in this manner with the addition of sodium chloroacetate. 

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]. 

Kurita et al. (2002) succeeded in introducing alkyl groups, such as methyl, ethyl, and pentyl groups, into chitin at the nitrogen of C2 acetamido moiety via an adjusted five-step modification process (Figure 5). Chitosan was completely deacetylated and treated with three types of aldehydes, namely formaldehyde (methanol), acetaldehyde (ethanol), and valeraldehyde (pen-tanol). The Schiff bases of chitosan were reduced to iV-alkylated chitosan using sodium cyanoborohydride (NaCNBH3). 

Chitin is an abundant natural biopolymer and exhibits excellent antimicrobial properties. To obtain enhanced antimicrobial properties, deacetylated products of chitin—chitosan (CS) have to be synthesised, which includes the introduction of alkyl groups to the amine groups to produce quaternised N-alkyl CS derivatives, the introduction of extra quaternary ammonium grafts to CS and modification with phenolic hydroxyl moieties. 

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