Abstract
An optimization of the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and hydroxy benzotriazole mediated conjugation of the polysaccharide chitosan with functional carboxylic acids was shown. Optimal parameters that enable resource-efficient synthesis of highly functionalized chitosan were identified. In particular, use of only catalytic instead of stoichiometric amounts of hydroxy benzotriazole and tight control of pH in reaction mixture resulted in highly efficient incorporation of the desired moieties as side chains in chitosan. As a result, the model reactant 4-azidobenzoic acid was incorporated resulting in a degree of substitution of over 30% with very high coupling efficacy of up to 90%. Similar results were obtained with other carboxylic acids such as methacrylic acid, 3-(2-furyl) propionic acid and 3-maleimido propionic acid, highlighting the broad applicability of our findings for the functionalization of chitosan.
Highlights
Chitosan (CS) is a polysaccharide consisting of β-1-4-linked N-acetyl-glucosamine (GlcNAc) and glucosamine (GlcN) repetition units
The carbodiimide mediated amidation reaction with ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/HOBt is a very attractive synthetic pathway for such a chitosan functionalization, which is often associated with an insufficient degree of substitution (DS), low coupling efficacy (CE) and undesirable high reagent consumption [2,3,4,5,6,8,9,10,11,15,19]
Our findings demonstrate the importance of using optimized parameters for functionalization of chitosan via carbodiimide chemistry
Summary
Chitosan (CS) is a polysaccharide consisting of β-1-4-linked N-acetyl-glucosamine (GlcNAc) and glucosamine (GlcN) repetition units. It is derived from chitin, a natural polymer occurring in insects, crustacean, and fungi. Shells of shrimps and lobsters are currently the main biological source for chitin. Fungi are another source of chitin that can be used for production of chitosan. Demineralization and deacetylation of chitin from marine organisms implicates high economic and ecological costs [1]. Chitin produced from fungal biomass represents a more reliable and ecofriendly alternative. The chitosan derived from the different sources typically have different properties such as degree of acetylation and molecular weight
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