Synthesis of Tosyl-Chitosan

Chitin powder isolated from crab shells (Sigma, Lot. C7170) was
purified by stirring in a 5% NaOH aqueous solution for 3 days, recovered with
deionized water to pH 7 and dried at 50 o C.

Preparation of chitin solution (1) and tosyl-chitin (2)
0.5g of Chitin (equiv. to 2.5 mmol of pyranose unit) and 1.3g of lithium chloride
(LiCl) dried respectively at 50 o C overnight and at 130 o C for 4h and cooled, and were
placed in a 100 ml three-necked flask fitted with rubber septa.
The flask was purged
with dry oxygen free nitrogen (OFN) and 26 ml of anhydrous DMAc was added via a
syringe.
The mixture was stirred at room temperature using a magnetic stirrer bar
until all solids were dissolved.
To the resultant chitin solution, was added Et 3 N (7.2
ml, 52mmol) followed by a solution of tosyl chloride (9.53g, 50mmol) in 12 ml
DMAc.
The reaction flask was transferred to the cold incubator and the reaction was
allowed to proceed at 8 o C for 24h at stirring speed of 250 rpm.
At the end of the
reaction, the mixture was filtered and the filtrate precipitated into 200 ml acetone,
washed with 300 ml methanol (100 ml × 3), 100 ml water (25 ml × 4) and 100ml
acetone.
The resulting product was freeze-dried to give 0.65g white color solid of
tosyl-chitin. The yield was 86.6%.