Some novel N-(carboxyacyl)chitosan filaments

A suspension of chitosan filaments in methanol was treated with each of maleic (1), (2-octen-1-yl)succinic (2), citraconic (3), phthalic (5), glutaric (4), and succinic (9) anhydrides to give rise to novel six N-(carboxyacyl)chitosan filaments (F1–F5 and F9) at d.s. 0.09–0.75 for N-carboxyacyl. However, no N-(carboxyacyl)chitosan filaments were obtained by treatment with each of trimellitic (6), 4-methylphthalic (7) and pyromellitic (8) anhydrides due to a steric hindrance in the chitosan filaments. On the other hand, chitosan was N-carboxyacylated in a solution of 2% aqueous acetic acid–methanol (1:1, v/v) with each of 1–9 to give rise to N-(carboxyacyl)chitosan derivatives C1–C9 (d.s. 0.39–0.80 for N-acyl) in 69–96% yields. Each of C1, C4–C7, C9 and F1 was soluble in water and in 1% aqueous sodium hydroxide solutions.