[13C,15N]2-Acetamido-2-deoxy-d-aldohexoses and Their Methyl Glycosides: Synthesis and NMR Investigations of J-Couplings Involving 1H, 13C, and 15N
摘要:
A series of 2-amino-2-deoxy-D-[1-C-13]aldohexoses and their methyl glycosides was prepared with use of a simplified cyanohydrin reduction route. Four D-aldopentosylamines (arabino, lyxo, ribo, xylo) were prepared from the corresponding D-aldopentoses by reaction with NH3(9) in MeOH solvent, isolated in solid form, and characterized by C-13 and H-1 NMR. Hydrolysis of beta-D-xylopyranosylamine was studied using C-13-labeled substrates to establish optimal solution conditions for cyanohydrin formation. Major hydrolytic intermediates were observed and identified by time-lapse 1D and 2D NMR analyses of reaction mixtures. The aldopentosylamines were subsequently employed in cyanohydrin reduction reactions with (KCN)-C-13 to yield C2-epimeric [1-C-13]2-aminosugars, which were separated by chromatography on ion-exchange columns. N-Acetylation and methyl glycosidation followed by chromatography gave pure 2-acet-amido-2-deoxy-D-[ 1-C-13]aldobexopyranosides. J(CH) and J(CC) spin-spin coupling constants involving the labeled anomeric carbon were measured and compared to those observed previously in methyl D-[1-C-13]-aldohexopyrano sides. In parallel studies, theoretical J-couplings were calculated in model N-acetylated aldopyranosides using density functional theory (DFT) to predict the effect of OH vs NHCOCH3 substitution at C2 on J(CH) and J(CC) values in aldopyranosyl rings. The synthetic method was also modified to accommodate N-15- and C-13-labeling within the N-acetyl side-chain, and some J-couplings involving 1H, C-13, and N-15 atoms in 2-[1,2-C-13(2);N-15]acetamido-2-deoxy-D-[1-C-13]glucose were measured and interpreted.
Synthesis of nitrogen-15-labeled 2-amino(glycofurano)oxazolines via glycosylamine intermediates
作者:Robert M. Davidson、Edward White、Sam A. Margolis、Bruce Coxon
DOI:10.1016/0008-6215(83)88113-0
日期:1983.6
Abstract A new, efficient synthesis of doubly 15N-labeled 2-amino-oxazoline derivatives of pentoses and hexoses has been delineated that involves treatment either of unprotected or O-isopropylidenated glycosylamines with cyanamide-15N2 in methanol to give 2-amino(glycofurano)oxazolines-15N2. A probable mechanism for these reactions is presented. These techniques provide a practical means by which a
First crystallographic evidence for the formation of β-d-ribopyranosylamine from the reaction of ammonia with of d-ribose
作者:Gudneppanavar Rajsekhar、Chebrolu P Rao、Philippe Guionneau
DOI:10.1016/s0008-6215(03)00006-5
日期:2003.4
Beta-D-Ribopyranosylamine was synthesized and characterized using analytical, spectral and single-crystal X-ray diffraction methods. The molecule exists in the chair form with the 4C(1) conformation. The beta anomeric form of C-1 is supported by the dihedral angles. The molecule exhibits both intra- and intermolecular hydrogen-bond interactions of the type O-H...O, Nz-H...O and C-H...O, and these are