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Determination of the Karplus relationships for the C‐2, H‐1′ and C‐6, H‐1′ vicinal coupling paths of uridine derivatives
Author(s) -
Davies David B.,
Rajani Pramila,
MacCoss Malcolm,
Danyluk Steven S.
Publication year - 1985
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.1260230204
Subject(s) - chemistry , vicinal , glycosidic bond , dihedral angle , proton , coupling (piping) , nucleoside , coupling constant , uracil , j coupling , computational chemistry , carbon 13 , stereochemistry , nuclear magnetic resonance spectroscopy , crystallography , hydrogen bond , molecule , organic chemistry , physics , mechanical engineering , dna , biochemistry , particle physics , quantum mechanics , engineering , enzyme
A number of uracil cyclo‐nucleosides with known glycosidic bond conformations have been synthesized as model compounds for evaluating the Karplus parameters of vicinal carbon‐proton coupling across the glycosidic bond. The magnitudes of 3 J (C‐2, H‐1′) and 3 J (C‐6, H‐1′) were determined from proton‐coupled 13 C NMR measurements, and both coupling constants showed an approximate Karplus dependence with dihedral angle. Careful analysis of the results on model compounds reveals that the C‐2, H‐1′ and C‐6, H‐1′ coupling paths are not equivalent, and so the magnitudes of Karplus parameters have been determined for each coupling path for the Karplus relationship in the form 3 J = A cos 2 θ + B cos θ + C , i.e. A 6 = 6.2, B 6 = −2.4 and C 6 = 0.1 Hz and A 2 = 5.0, B 2 = 2.1 and C 2 = 0.1 Hz. Comparison is made between proton‐carbon coupling magnitudes in nucleoside and peptide coupling paths.