C—1H Coupling

C-0-C-1H couplings have been determined in methyl /i-cellobioside after deuterium substitution of all protons on carbon atoms with a free hydroxy group. Assuming a Karplus type relationship between 3JC H and the dihedral angle in 13C-0-C-1H groups, the torsional angles 0 and / of methyl / -cellobioside were determined to be 25 30" [734],... 

The DD-CSA cross-correlated relaxation, namely that between 13C-1H dipole and 31P-CSA, can also be used to determine backbone a and C angles in RNA [65]. The experiment requires oligonucleotides that are 13C-labeled in the sugar moiety. First, 1H-coupled, / - DQ//Q-II CP spectra are measured. DQ and ZQ spectra are obtained by linear combinations of four subspectra recorded for each q-increment. Then, the cross-relaxation rates are calculated from the peak intensity ratios of the doublets in the DQ and ZQ spectra. The observed cross-correlation rates depend on the relative orientations of CH dipoles with respect to the components of the 31P chemical shift tensor. As the components of the 31P chemical shift tensor in RNA are not known, the barium salt of diethyl phosphate was used as a model compound with the principal components values of -76 ppm, -16 ppm and 103 ppm, respectively [106]. Since the measured cross-correlation rates are a function of the angles / and e as well, these angles need to be determined independently using 3/(H, P) and 3/(C, P) coupling constants. 

In contrast, the analogous reaction with NaTp affords exclusively the monomeric complex 461, in which fluxionality of the K2-Tp ligand was noted in the temperature range 28 to —31 °C.142 Moreover, free rotation of the 2-picolyl ligand was inferred from the equivalence of the methylenic protons (cf. inequivalent in 459, 460, and the parent), and a discernible 3lP—1H coupling of 5 Hz confirmed a cis disposition relative to the PPh3 ligand. 

In the 1H-coupled spectrum, the peaks for C-1 and C-2 would be triplets, and the C-3 peak would be a quartet. 

K. Bock and C. M. Pedersen, Two- and three-bond 13C—1H couplings in some carbohydrates, Acta... 

Palladium complexes of TPPTS and TPPMS have been employed extensively as catalysts for carbonylation, hydroxycarbonylation, and C—C cross-coupling reactions (cf. Section 6.6). Hydroxycarbonylation of bromobenzene in biphasic medium using Pd(TPPTS)3 as catalyst yields benzoic acid, which remains in the aqueous phase, thus avoiding the direct recycling of the catalyst [59]. The formation of Pd(TPPTS)3 from PdCl2 and TPPTS in aqueous solution has been studied in detail by 170, 1H 31P, and 35C1 NMR spectroscopy. The complex [ PdCI(TPPTS)3 Cl obtained initially is reduced by excess TPPTS, TPPTSO being formed. A more attractive synthesis of Pd(TPPTS)3 involves the facile reduction of [PdCl-(TPPTS)3]+C1- with CO (Scheme 1) [60],... 

Feeney, J., Hansen, P. E., and Roberts, G. . K. (1974). Chem. Comm. 465. Use of 1 3 C-1H Spin-Coupling Constants in the Determination of Side-Chain Conformations of Amino-Acids. 

Representative examples (a) Serianni, A. S., Wu, J., Carmichael, I. (1995). One-bond 13C-1H spin-coupling constants in aldofuranosyl rings effect of conformation on conpling magnitnde. Journal of the American Chemical Society, 117, 8645-8650. (b) Church, T. J., Carmichael, L, Serianni, A. S. (1997). XT- H and C- Spin-Coupling Constants in Methyl P-D-Ribofiiranoside and Methyl 2-Deoxy-P-D-cryf/jn9-pentofnranoside Correlations with Molecular Structure and Conformation. Journal of the American Chemical Society, 119, 8946-8964. (c) Tvaroska,... 

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