3 , 6 - Anhydroglucosaminyl Formation in Mucopolysaccharides ( keratosulfates / heparin )

Treatment of keratosulfates with alkali leads to the formation of 3,6-anhydroglucosaminyl groups in high yield. A similar reaction takes place with heparin and heparitin sulfate, though to a lesser extent. The anhydrosugar was isolated and compared with synthetic 3,6-anhydroglucosamine. The isolated compounds were identical in ion exchange chromatography in the amino acid analyzer and on Dowex 50 H+ eluted with dilute HCl. The spectra of the isolated and synthesized anhydrosugar were identical in infrared and nuclear magnetic resonance. Derivatized compounds were identical in gas-liquid chromatography and mass spectroscopy. The peracetylated compound isolated from keratosulfate gave the nuclear magnetic reasonance and fragmentation pattern of the postulated compound. The reaction is expected to be useful in structural studies of hexosamine-containing polymers. The sulfate ester groups of a number of polysaccharides substituted in the 6-position of a galactosyl moiety have been cleaved in an SN2 displacement by alkoxide ion with the concomitant formation of 3,6-anhydrosugar (1, 2). Our laboratory has been engaged for a considerable time in a search for an analogous reaction of hexosaminyl moieties in mucopolysaccharides substituted by sulfate in the 6-position and containing a free hydroxyl group in the 3-position. This condition is fulfilled in the keratosulfates (3-5), heparin (6), and, presumably, heparitin sulfate (7, 8). In this communication, the formation of 3,6-anhydroglucosamine by displacement of sulfate in polymers is described for the first time. The reaction will be useful in the fragmentation of these compounds by mild acid hydrolysis. 3,6-anhydro-D-glucosamine was shown by its typical appearance in the amino-acid analyser, by its elution with dilute acid from Dowex 50, by its infrared (IR) and nuclear magnetic resonance (nmr) spectrum, by gas-liquid chromatography (GLC), and by mass spectroscopy.