Chemoselective Protection of the Amino Groups of Chitosan by Controlled Phthaloylation:  Facile Preparation of a Precursor Useful for Chemical Modifications

• Published in: Biomacromolecules Vol. 3; no. 1; pp. 1 - 4
• Main Authors: Kurita, Keisuke, Ikeda, Hiroyuki, Yoshida, Yuya, Shimojoh, Manabu, Harata, Manabu
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.01.2002
• Subjects: Acetylation; Chitin - analogs & derivatives; Chitin - chemistry; Disaccharides - chemistry; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Models, Chemical; Phthalic Acids - chemistry; Solubility; Spectrophotometry, Infrared; X-Ray Diffraction
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm0101163

A simple and convenient procedure for chemoselectively protecting the amino groups of chitosan has been developed to provide N-phthaloyl-chitosan that is indispensable as a soluble N-protected precursor for further controlled modification reactions of chitosan. Although the conventional N-phthaloylation of chitosan in N,N-dimethylformamide was accompanied by partial phthaloylation of the hydroxy groups, the addition of a small amount of hydroxy-containing compounds effectively suppressed the O-phthaloylation. Of some compounds examined, water proved particularly suitable, resulting in the formation of chemoselectively N-phthaloylated chitosan without any appreciable O-phthaloyl groups. The resulting N-phthaloyl-chitosan was found to be crystalline despite the presence of a bulky substituent. A solubility test indicated that N-phthaloyl-chitosan exhibited considerable affinity for organic solvents.