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Conformational dependence of the one‐bond carbon–proton coupling constants in oligosaccharides
Author(s) -
Hricovíni Miloš,
Tvaroška Igor
Publication year - 1990
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260281005
Subject(s) - chemistry , dihedral angle , conformational isomerism , coupling constant , anomer , proton , crystallography , carbon fibers , computational chemistry , stereochemistry , molecule , hydrogen bond , organic chemistry , physics , materials science , particle physics , quantum mechanics , composite number , composite material
A study is presented of the dependence on conformation of one‐bond carbon‐proton coupling constants in three 1‐4‐linked disaccharides. Calculated 1 J (CH) values are based on the FPT formulation in the semi‐empirical INDO MO method. The configuration at the anomeric carbon influences the 1 J (CH) value, and the 1 J (C‐1′, H‐1′) values are 20–30 Hz higher than the 1 J (C‐4, H‐4) values. The conformational dependence of 1 J (CH) on the dihedral angle about the CO bonds is satisfactorily expressed in the analytical form 1 J (CH) = A cos 2ϕ + B cos ϕ. The constants A‐E are different for the α‐ and β‐anomers. Calculated average values 〈 1 J (C‐1′, H‐1′)〉 = 163.7 Hz and 〈 1 J (C‐4, H‐4)〉 = 146 Hz for methyl β‐xylobioside using PCILO‐calculated abundances of conformers agree well with the experimental values of 162.7 and 147.5 Hz, respectively.