Chondroitin methylation

Chondroitin sulphate and methylated chondroitin methyl ester, modified by oxidation with bromide-water or by reduction with sodium borohydride, have been used as substrates for chondroitinases from Arthrobacter and Flavobac-tenum species. 

The methylated derivatives served as the basis of elegant studies in which Jeanloz and his colleagues unequivocally established the structure of hyaluronan, dermatan sulfate, and the chondroitin sulfates. They also clarified many confusing issues, including the position of the sulfate groups in these polymers. In the course of this work, they proved that dermatan sulfate contained L-iduronic acid, a sugar not known before to occur in nature. 

The downfield displacement of the C-6 resonance of chondroitin on O-sulfation was 6.5 p.p.m., close to the 6.6 p.p.m. observed on 6-0-substitution of 3-D-glucose.152 As may be seen from Table VI, O-sulfation of a,j8-D-glucose and methyl 3-O-methyl-a-D-mannopyranoside153 causes a strong, downfield shift of the substituted resonance that is accompanied by smaller, upfield displacements of the signals of adjacent carbon atoms. Other, more-distant, substitution effects were not observed, except for the C-2 and OMe-3 signals on 4-O-sulfation of the D-mannopyranoside derivative. 

Karst N, Jacquinet JC. Stereo-controlled total synthesis of shark cartilage chondroitin sulfate D-related tetra- and hexasaccharide methyl glycosides. Eur J Org Chem 2002 815-825. 

On the basis of the results of methylation, periodate oxidation, and oxidative deamination with ninhydrin, the structure shown above is proposed 50, 51a, 611)) for the repeating unit of chondroitin sulfate A. 

Polysaccharides containing carboxyl groups, such as chondroitin sulfate and hyaluronic acid, are derivatized with cysteine methyl ester by substituting carboxyl groups of polysaccharides and subsequently cross-linked by mild oxidation to form hydrogels. IPNs and semi-lPNs can also be degraded from backbone. 

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