Abstract: This invention relates to a novel method of preparation of hyaluronic acid derivatives by means of a reaction of the hyaluronic acid with the complex (O-acyl-O?-alkyl carbonate-substituted pyridine) of the general formula R—CO—O—CO—O—R1 and R25C5N. The reaction takes place in DMSO in the presence of an external base, forming O-acylated products. The method leads to higher substitution degrees and shorter reaction times compared to the known analogues, hi case the agent comprises two or more functional groups R(CO—O—CO—O—R1)n, crosslinked hyaluronic acid derivatives are formed.

Abstract: The invention relates to the modification of hyaluronic acid by means of a protonized DTPA bis anhydride in a non-basic polar aprotic solvent in absence of any external base to form crosslinked products. The reaction runs via the formation of a complex and the acylating agent is the hyaluronan co-cation itself, i.e. protonized DTPA bis anhydride. The final crosslinked derivative (linker) comprises three carboxylic groups and three tertiary amines which are capable of complexing various metals effectively. The final DTPA crosslinked hyaluronic acid may also be hydrophobized by means of mono, bis or tris functional alkylating agents.