Karplus equation proton-carbon couplings

I. Tvaroska, M. Hricovmi, and E. Petrakova, An attempt to derive a new Karplus-type equation of vicinal proton-carbon coupling constants for C-O-C-H segments of bonded atoms, Carbohydr. Res., 189 (1989) 359-362. 

Vicinal proton-carbon coupling constants (3.7h65,C4 and J is.v.ci) also provide valuable information about the hydroxymethyl conformation. Theoretical calculations were applied to establish Karplus-type equations that correlate these couplings with lu torsion angle and then these were used to estimate C5—C6 rotamer... 

Applications of n.m.r. in biological and medicinal chemistry. Many conformational and configurational problems have been solved by use of the Karplus equation which correlates the coupling constant between vicinal protons with the torsional angles (defined in Section 13.3) between different carbon-hydrogen planes (Karplus, 1959 Roberts, 1968). In this way, each of the four isomers of cocaine (j.ii) was assigned a conformation (Sinnema et al, 1968). 

Karplus-type equations have been developed for many other systems of interest, most notably H-C-O-H [242,243], H-C-O-C [387,414,415], H-C-C-C [197,387], and C-O-C-C [416, 417], It should be noted that coupling to hydroxyl protons can be observed in water or water/acetone or water/DMSO mixtures if the NMR tubes are rinsed in phosphate buffers and the carbohydrate derivatives are thoroughly deionized [239,249], If the magnitudes of the coupling constants to carbon are determined on natural abundance material, considerable amounts are required. Alternatively, labeled material can be used [416,417,418,419] and starting materials with varieties of labels are available. 

I. Tvaroska, K. Mazeau, M. Blanc-Muesser, S. Lavaitte, H. Driguez, and F. R. Taravel, Karplus-type equation for vicinal carbon-proton coupling constants for the C-S-C-H pathway in 1-thioglycosides, Carbohydr. Res., 229 (1992) 225-231. 

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