O-oligosaccharidyl-1-amino-1-deoxyalditols as intermediates for fluorescent labelling of oligosaccharides

Reducing monosaccharides were efficiently converted to stable 1-amino-1-deoxyalditols (=glycamines; distinguished from glycosylamines by mass-spectrometry) during incubation at 20 degrees C in saturated aqueous NH(4)HCO(3) containing NaCNBH(3). Potentially useful by-products included a novel, fully-reduced dimer (the corresponding secondary glycamine) and several relatively long-lived, unreduced products. With increasing incubation time, monomers exceeded dimers. Reducing disaccharides and oligosaccharides underwent similar reactions at their reducing termini; the yield of dimers decreased with increasing oligosaccharide M(r). The O-oligosaccharidyl-1-amino-1-deoxyalditols (OADs) obtained by reductive amination of oligosaccharides reacted readily with lissamine rhodamine sulfonyl chloride to yield OAD-sulforhodamine conjugates linked by a stable sulfonamide bond. Conditions for this reaction were optimised (borate buffer, pH9.0-9.5). The highly fluorescent OAD-sulforhodamine products were purified on a C(18) cartridge. They were electrophoretically immobile at pH2.0 and 6.5, and migrated towards the anode in borate buffer, pH9.4. The OAD-sulforhodamines were amenable to TLC and were excellent substrates for enzymic transglycosylation and for glycosylhydrolase action.