Syntheses of model oligosaccharides of biological significance. XII. Synthesis, NMR, and conformational analysis of trideuteriomethyl 4-O-(β-D-mannopyranosyl)- 2-acetamido-2-deoxy-β-D-glucopyranoside: the use of DEPT ¹H to ¹³C transfer for T₁ measurements and NOE assignments of tightly coupled ¹H nuclei

Abstract

Ho HUAT LEE, LIGAYA N. CONGSON, DENNIS M. WHITFIELD, LAJOS R. RADICS, and JIRI J. KREPINSKY. Can. J. Chenl. 70, 2607 (1992).The title disaccharide Manp(p1-4)GlcpNAcpl-OCD, has been prepared by a short synthetic sequence through the inversion of configuration from gluco to marzrzo involving benzyl Glcp(p1-4)GlcpNAc. The disaccharide was subjected to detailed high-field 'H and I3c NMR study. First, conventional and 2D spectra were run to afford a co~nplete set of assigned spectral parameters. Next, steady-state 'H-{'H} NOE and 'H, ',c spin lattice relaxation experiments were performed to infer dynamic spectral data related to ~nolecular conformation. Owing to tight couplings and signal overlaps in the 'H spectrum, proton relaxation and selected NOE data were obtained via "C NMR after transfer of the actual, non-equilibrium, proton magnetization to the "C frequency domain. Using this experimental approach it has been found that T,'s for Manp H-4 and GlcpNAc H-2 were substantially longer than those of the other sugar ring protons, and that the principal interresidue dipolar contact in Manp(p 1 -4)GlcpNAcp 1 -OCD3 takes place between Manp H-l and

Strategies of Synthetic Methodologies for Constructing β-Mannosidic Linkage

“…This led Lindberg to synthesize β-mannosides [126]. Various oligosaccharides were obtained by glucosylation, selective deprotection of the 2-O, oxidation and reduction to give β -mannoside oligosaccharides [125][126][127][128][129][130][131][132][133][134][135][136][137][138]. The Ac 2 O/DMSO was frequently used as oxidant and sodium borohydride or lithium-tri-sec-butylbromide as reducing agents.…”