Preparation and evaluation of trimethylsilylated chitin as a versatile precursor for facile chemical modifications

Trimethylsilylation of chitin was studied in detail to establish a reliable method, and the properties of the resulting product were elucidated. Chitin was successfully trimethylsilylated with a mixture of hexamethyldisilazane and trimethylsilyl chloride in pyridine. Compared to alpha-chitin, beta-chitin was much more reactive and advantageous as a starting material to prepare fully substituted chitin in a simple manner, though alpha-chitin also underwent full silylation under appropriate conditions. The resulting silylated chitin was characterized by marked solubility in common organic solvents and by easy desilylation to regenerate hydroxy groups, which enabled clean preparation of chitin films. The reactivity of the silylated chitin was examined by treating with triphenylmethyl chloride and acetic anhydride as typical alkylating and acylating reagents, and complete substitutions were readily accomplished. The silylated chitin has thus proved to be a superb precursor for modification reactions.