Analysis of pyruvylated β-carrageenan by 2D NMR spectroscopy and reductive partial hydrolysis Original Research Article

A polysaccharide rich in 4′,6′-O-(1-carboxyethylidene)-substituted (i.e., pyruvylated) β-carrageenan has been prepared by solvolytic desulfation of a polysaccharide containing predominantly pyruvylated α-carrageenan, which was extracted from the red seaweed, Callophycus tridentifer. The 13C and 1H NMR chemical shifts of pyruvylated β-carrageenan have been fully assigned using 2D NMR spectroscopic techniques. The 4′,6′-O-(1-methoxycarbonylethylidene) group, generated during chemical methylation of the polysaccharide, has been shown to survive under the conditions of acidic hydrolysis that cleave the 3,6-anhydro-α-d-galactosidic bonds in permethylated samples of both pyruvylated β- and pyruvylated α-carrageenans. As a result, two novel pyruvylated carrabiitol derivatives have been prepared.