Synthesis of an O-alkynyl-chitosan and its chemoselective conjugation with a PEG-like amino-azide through click chemistry


N-Phthaloyl-chitosan O-prop-2-ynyl carbamate was prepared as a biopolymer amenable to undergo chemoselective conjugation by azide-alkyne coupling, while allowing upturn of chitosan's amines after dephthaloylation. N-phthaloylchitosan was prepared according to previously described methods and, due to its low solubility in current organic media, subsequent modifications were run in heterogeneous conditions. Activation of hydroxyls with carbonyl-1,1 '-diimidazole and coupling to propargylamine yielded N-phthaloyl-chitosan O-prop-2-ynyl carbamate, then coupled to a model PEG-like azide by azide-alkyne coupling, giving the expected triazolyl conjugate. N-Dephthaloylation allowed recovery of the free amines, responsible for chitosan's bioadhesion and tissue-regeneration properties. The structures of all polymers were confirmed by Fourier-transformed infra-red (FT-IR) and X-ray photoelectron (XPS) spectroscopies, as well as by solid-state nuclear magnetic resonance (SSNMR). All chitosan derivatives were poorly soluble in both aqueous and organic media, which makes them suitable for topical applications or for removal of toxic substances from either the gastric intestinal tract or environmental sources. (C) 2011 Elsevier Ltd. All rights reserved.




Chemistry; Polymer Science


Oliveira, JR; Martins, MCL; Mafra, L; Comes, P

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The authors thank Fundacao para a Ciencia e Tecnologia (FCT, Portugal) and FEDER (European Union) for co-funding this project (ref. PTDC/CTM/65330/2006 and ref. FCOMP-01-0124-FEDER-007135). PG thanks FCT for pluri-annual funding to Research Unit CIQUP. LM acknowledges FCT for financing the Portuguese NMR network (ref. REDE/1517/RMN/2005) and the project PTDC/QUI-QUI/100998/2008, which allowed the use of the NMR facilities, efficiently. The authors are also indebted to Drs. Cristina Barrias (INEB) and Eliandre de Oliveira (Parc Cientific de la Universitat de Barcelona, Spain) for collaboration in molecular weight analysis by HP-SEC and MALDI-TOF MS, respectively.

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