IMMUNOCHEMICAL STUDIES ON BLOOD GROUPS .40. SCISSION OF OLIGOSACCHARIDES BY SODIUM HYDROXIDE IN PRESENCE OF SODIUM BOROHYDRIDE - A MODEL FOR DEGRADATION OF BLOOD-GROUP SUBSTANCES

To assess the competition between reduction and elimination at each step in the peeling of the carbohydrate chains from blood-group A, B, H, and Le2 substances by sodium hydroxide-sodium borohydride, the amount of scission of some model compounds, namely, oligosaccharides containing the various sugar linkages in blood-group substances, was studied. The extent of cleavage was estimated by determining the reduced, eliminated residues by gas chromatography of their per(trimethylsilyl) derivatives. β-D-Galp-(1→3)-D-GNAc (1) and β-D-Galp-(1→3)-D-GalNAc (2) were found to be the most labile of such disaccharides, showing about 50 per cent cleavage. At 4°, reactions were slower, and there was less scission, than at 24°. β-D-GNAcp-(1→3)-D-Gal (5) is also labile, but is cleaved to a much smaller extent (7%). β-D-Galp-(1→4)-D-GNAc (3) and β-D-GNAcp-(1→6)-D-Gal (4) are stable. The oligosaccharides isolated fr om blood-group substances are considered in terms of the extent of peeling to be expected from the results obtained with the model compounds. Products from the reducing residues of the disaccharides were observed by gas-liquid and paper chromatography. © 1969.