Novel N-saturated-fatty-acyl derivatives of chitosan soluble in water and in aqueous acid and alkaline solutions

Novel N-saturated fatty acyl derivatives of chitosan soluble in water and in aqueous alkaline and acid solutions were prepared in 45–72% yields by N-deacylation of sodium N-acylchitosan salts, and in 75–85% yields by N-acylation of chitosan. The N-acyl derivatives soluble in water and 2% aqueous sodium hydroxide were in the degree of substitution (d.s.) ranges of 0.42–0.82 (d.s. 0.40 in width) for N-acetyl, 0.37–0.76 (d.s. 0.39 in width) for N-propionyl, 0.52–0.71 (d.s. 0.19 in width) for N-butyryl and 0.54–0.64 (d.s. 0.10 in width) for N-pentanoyl, and 0.58 (narrow d.s. in width) for N-hexanoyl. The N-acyl derivatives soluble in 2% aqueous acetic acid were in the d.s. ranges of <0.82 for N-acetyl, <0.76 for N-propionyl, <0.71 for N-butyryl, <0.64 for N-pentanoyl, <0.58 for N-hexanoyl, <0.41 for N-octanoyl, <0.24 for N-decanoyl, <0.15 for N-lauroyl, <0.05 for N-myristoyl. However, N-palmitoyl and N-stearoyl derivatives in all the d.s. ranges were insoluble in water, 2% aqueous sodium hydroxide and 2% aqueous acetic acid solutions.