One-bond carbon-proton coupling constants
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Summary The angular dependence of1JC,H in model compounds related to β-linked oligosaccharides has been established by FPT INDO quantum chemical calculations. Values calculated for models of (1 → 1)-, (1 → 2)-, (1 → 3)- and (1 → 4)-linked disaccharides were compared, and the effect of the orientation of HO-2 elucidated. The angular dependence of1JC,H on the torsional angles ΦH and ΨH and the solvent dielectric constant (s) was characterized in the form:1JC,H = A cos2ϖ+B cosϖ + C sin2ϖ + D since + E + Fe. The1JC,H values, measured by DEPT methods for C-1-H-1 and C-X′-H-X′ in cellobiose, cyclic trisaccharide and hexopyranoses were used to adjust the calculated angular dependences. Based on the occurrence of the conformers for agarobiose, neoagarobiose, mannobiose and methyl β-xylobioside, the thermodynamically averaged 〈1JC,H 〉 values were calculated. The results obtained (〈1JC-1,H-1 〉 162.4, 〈1JC-4′, H-4′ 〉 147.6 Hz for methyl β-xylobioside; 〈1JC-1,H-1 〉 162.4 and 〈1JC-4′,H-4′] 〉 147.6 Hz for mannobiose; 〈1JC-1,H-1 〉 162.8 Hz for neo agarobiose and 〈1JC-1,H-1 〉 163.2 Hz for agarobiose) agree well with the experimental values of 162.7, 147.5, 160.4, 147.2, 160.9 and 165.7 Hz, respectively.
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