Paul N. Sanderson

Fast-atom-bombardment mass-spectrometric strategies for sequencing sulphated oligosaccharides

Abstract A strategy is presented for the structural analysis of sulphated oligosaccharides. The oligosaccharides are permethylated to leave sulphate groups intact, and the products examined by negative f.a.b.-m.s. The fragmentation observed from such compounds in the negative mode is described for the first time. The sulphates are then chemically replaced by acetyl groups, so producing a derivative that is examined in the positive mode. This procedure yields sequence data and defines the residues on which the sulphates were originally located. The strategy is illustrated using glycosaminoglycan fragments.

Conformational equilibrium of unsulphated iduronate in heparan sulphate tetrasaccharides

Proton-proton coupling constants for terminal α-l-iduronate residues in tetrasaccharides obtained from heparan sulphates by complete nitrous acid deaminative cleavage were shown to vary with experimental conditions. It is proposed that the iduronate residue is in a conformational equilibrium between the1C4 chair and either the2So skewboat or possibly the2H3 half-chair conformers. It was not possible to discriminate between the two non-chair forms empirically. The position of the equilibrium is sensitive to temperature, pH and sulphation of neighbouring residues. The likelihood of iduronate residues within glycosaminoglycans existing in the4C1 conformer in addition to the1C4 and2So forms is discussed.

N.M.R. studies of the disulphated disaccharide obtained by degradation of bovine lung heparin with nitrous acid

The disulphated disaccharide IdoA(2SO3)-anManOH(6SO3) was prepared from bovine lung heparin by treatment with nitrous acid followed by borohydride reduction. The 1H- (400 MHz) and 13C-n.m.r. (100 MHz) spectra of this disaccharide derivative have been assigned completely using homonuclear spin-decoupling experiments, 13C-1H correlations, and a COSY-45 two-dimensional homonuclear correlation experiment. The 3JH,H values show that the IdoA(2SO3) residue exists in a single conformation throughout the temperature range 20-90 degrees.

N.M.R. studies of oligosaccharides obtained by degradation of bovine lung heparin with nitrous acid

The oligosaccharides IdoA(2SO3)-[GlcNSO3(6SO3)-IdoA(2SO3) ]n-anManOH(6SO3) (n = 1-4) have been prepared from bovine lung heparin by treatment with nitrous acid followed by borohydride reduction and then fractionation by gel filtration. The major resonances of the 1H- (400 MHz) and 13C-n.m.r. (100 MHz) spectra for each oligosaccharide fraction have been assigned using two-dimensional COSY, NOESY, and 13C-1H correlation experiments. The 1H resonances, representing the three distinct molecular environments of IdoA(2SO3), namely, at the non-reducing terminus, adjacent to the reducing terminal anManOH(6SO3), and in the [GlcNSO3(6SO3)-IdoA(2SO3)] repeat sequence, have been assigned.

Assignment of the 1H, 19F, and 13C NMR spectra of 2-deoxy-2-fluoro-d-ribose and characterisation of the isomeric equilibrium

Abstract The assignment of the 1 H, 19 F, and 13 C NMR chemical shifts and coupling constants of 2-deoxy-2-fluoro- d -ribose, an important intermediate in the synthesis of antiviral nucleoside drugs, is reported and the NMR spectra are used to determine the proportions of the pyranose and furanose forms together with the anomeric ratios in acetone- d 6 solution. The β-pyranose isomer is shown to exist at equilibrium with both 4 C 1 and 1 C 4 conformations in approximately equal proportions in fast exchange. The α-pyranose isomer at equilibrium is predominantly in the 4 C 1 form but the 1 C 4 conformer is also present in solution, the two forms being in intermediate exchange on the 19 F NMR timescale but in fast exchange on the 1 H and 13 C NMR timescales. For both the pyranose and furanose forms, the β-anomer predominates. The results are similar to those for d -ribose.