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Sign determination of the two-bond 15N-15N spin-spin coupling constant of a pyrimidine ring by a selective 15N decoupling technique

✍ Scribed by Yoshihiro Kuroda; Yasuhiro Fujiwara

Publisher: John Wiley and Sons
Year: 1987
Tongue: English
Weight: 296 KB
Volume: 25
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260250413

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✦ Synopsis

The sign 'J(NN) of 2-chlor0-6-methyl-['~N,]pyrimidine has been determined by 'H-('H (selective), "N (selective)} and 13C-(1H (noise), I5N (selective)} triple resonance techniques. The sign was proved to be negative (-1.6 Hz); consequently, chlorine substitution at C-2 was found to make ' . I ( " ) more negative, since the magnitude of 'J(NN) of ['5N,] pyrimidine is nearly equal to zero. It is stressed that sign determination for the spin couplings between hetero-nuclei is easier to perform when the resonance of one of the hetero-nuclei is irradiated than when that due to a proton is irradiated.

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## Abstract The first successful observation of the vicinal ^15^N,^13^C spin‐coupling constants in a series of amino acids, comprising Val, Ile, Leu and Thr, in which the α‐nitrogens are fully replaced with ^15^N, is described. A Karplus‐type dihedral‐angle dependence was noted for the coupling con