Patent ID: 8557986

Claim:
A method of producing a polysaccharide derivative comprising a polysaccharide having a carboxyl group bound to an organic compound having a functional group capable of condensing with the carboxyl group, which comprises reacting the polysaccharide with the organic compound by the use of a condensing agent shown by the general formula (1): wherein R 1 and R 2 independently represent a substituent selected among alkyl groups of 1 to 4 carbon atoms and aryl groups of 6 to 8 carbon atoms; Z − represents a counter anion; and E + represents the following group: wherein R 3 , R 4 , and R 5 independently represent an organic group having at least one carbon atom directly bound to the quaternary nitrogen atom and any two or all of R 3 , R 4 , and R 5 may link together to form a cyclic structure, wherein the polysaccharide having a carboxyl group is a hyaluronic acid having a weight average molecular weight of 100,000 to 5,000,000, and wherein the rate of the introduced organic compound per disaccharide unit of the hyaluronic acid is not less than 5%.