title: Chemoselective protection of the amino groups of chitosan by controlled phthaloylation: facile preparation of a precursor useful for chemical modifications.
abstract: 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.
authors.affiliation: Department of Applied Chemistry, Faculty of Engineering, Seikei University, Musashino-shi, Tokyo 180-8633, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kurita
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ikeda
authors.forename: Yuya
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Manabu
authors.initials: M
authors.lastname: Shimojoh
authors.forename: Manabu
authors.initials: M
authors.lastname: Harata
mesh_terms: D000107:Acetylation; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry; D004187:Disaccharides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010795:Phthalic Acids / Q000737:chemistry*; D012995:Solubility; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction
chemical_list: D004187:Disaccharides; D010795:Phthalic Acids; D002686:Chitin; C012492:phthalonic acid