Trimethylsilylation of chitosan and some properties of the product

Chitosan was trimethylsilylated, and some properties of the product such as solubility and reactivity were examined. Trimethylsilylation proceeded efficiently with a mixture of hexamethyldisilazane and chlorotrimethylsilane in pyridine; chitosan prepared from β-chitin underwent substitution more facilely than that from α-chitin. The degree of trimethylsilylation per pyranose unit reached 2.9. The resulting silylated derivative was almost soluble in pyridine and swelled considerably in common organic solvents. Though the product was hydrolytically stable in neutral and weakly alkaline media, it was deprotected readily with acid. As a typical example of modification reactions, acetylation of silylated chitosan was examined, and highly acetylated derivatives were obtained under mild conditions, indicating a high potential of the silylated chitosan as a precursor for chemical modifications of chitosan in organic solvents.