O-maleoyl derivative of low-molecular-weight κ-carrageenan: Synthesis and characterization

Low-molecular-weight (LMW) κ-carrageenan was achieved through mild hydrochloric acid hydrolysis of κ-carrageenan. The acylation of low-molecular-weight κ-carrageenan was performed by use of tetrabutylammonium (TBA) salt of the anionic polysaccharide fragments, maleic anhydride, 4-dimethylaminopyridine and tributylamine under homogeneous conditions in N,N-dimethylformamide at 60 °C. Analysis of FT-IR spectrum of O-maleoyl κ-carrageenan showed that a monoester derivative with maleoyl group was formed when LMW κ-carrageenan reacted with maleic anhydride. Investigation of 1H NMR spectroscopy revealed that the maleoylation took place regioselectively at C-2 of the κ-carrageenan 3-linked unit.