title: Regioselective pivaloylation of N-phthaloylchitosan: a promising soluble intermediate for chitosan chemistry.
abstract: A simple and efficient pivaloylation of primary alcohols was realized on N-phthaloylchitosan that was regioselectively and entirely protected. The selectivity of this mild esterification was demonstrated by comparison with (1)H NMR chemical shifts of H-1 and H-3 of complete 3,6-O-dipivaloylated derivatives. The selective hydrazinolysis of N-phthaloyl groups in the presence of pivaloyl ester was achieved in ethanol/water. High molecular weight 6-O-pivaloylchitosan, purified by ultrafiltration, with solubility in organic solvents was obtained. The selective introduction of a phosphorus moiety in O-3 using chlorodiphenylphosphine has led to 3-O-diphenylphosphinito-N-phthaloyl-6-O-pivaloylchitosan with a ds of 0.97 from energy dispersive X-ray spectroscopy, which demonstrates the potential applications of O-6 pivaloyl protection. The pivaloylation of O-6 alcohols can enhance the solubility of some chitosan derivatives and therefore contributes to the development of applications involving chitosan through regioselective modifications of alcohol and amino groups.
authors.affiliation: Département de Biologie, chimie et géographie, Université du Québec à Rimouski, 300, Allée des Ursulines, Rimouski, Québec, Canada G5L 3A1.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Babin
authors.forename: Amélie
authors.initials: A
authors.lastname: Ruest
authors.forename: Guillaume
authors.initials: G
authors.lastname: Drouin
authors.forename: Kathleen
authors.initials: K
authors.lastname: Sirois
authors.forename: Steeven
authors.initials: S
authors.lastname: Ouellet
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gagnon
mesh_terms: D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry; D006834:Hydrazines / Q000737:chemistry; D010421:Pentanoic Acids / Q000737:chemistry; D012995:Solubility; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D006834:Hydrazines; C483239:N-phthaloylchitosan; D010421:Pentanoic Acids; D002686:Chitin; C029424:hydrazine