13C-2H coupling

Fig. 1. Typical values for the scalar couplings in perdeuterated proteins, which can be used for the coherence transfer through the spin system (a). Strategies for obtaining resonance assignment in 15N/13C/2H labelled proteins discussed in this chapter (b). The boxes, circles, and triangles indicate correlations established in the corresponding pulse scheme.

Configurational assignments for 5,6-dihydro-2H-pyrans have also been made from the magnitude of the geminal 13C-H coupling constants (73TL1037) and from the sensitivity of the chemical shift to steric hindrance (B-72MI22202). 

In the solid, dynamics occurring within the kHz frequency scale can be examined by line-shape analysis of 2H or 13C (or 15N) NMR spectra by respective quadrupolar and CSA interactions, isotropic peaks16,59-62 or dipolar couplings based on dipolar chemical shift correlation experiments.63-65 In the former, tyrosine or phenylalanine dynamics of Leu-enkephalin are examined at frequencies of 103-104 Hz by 2H NMR of deuterated samples and at 1.3 x 102 Hz by 13C CPMAS, respectively.60-62 In the latter, dipolar interactions between the 1H-1H and 1H-13C (or 3H-15N) pairs are determined by a 2D-MAS SLF technique such as wide-line separation (WISE)63 and dipolar chemical shift separation (DIP-SHIFT)64,65 or Lee-Goldburg CP (LGCP) NMR,66 respectively. In the WISE experiment, the XH wide-line spectrum of the blend polymers consists of a rather featureless superposition of components with different dipolar widths which can be separated in the second frequency dimension and related to structural units according to their 13C chemical shifts.63... 

In this case ylide complexes are not observed and therefore the reactions are very simple. When L 2-methylpyridine or acetonitrile, the product was shown to be (XII) rather than (XIII). Complex (XII) could be characterised directly by lU and 13C NMR spectroscopy or, more simply, treated with triphenylphos-phine to release the alkene. Figure 1 shows the 13C XH NMR spectrum of the released alkene (together with 2-methylpyridine), which clearly shows 1 1 1 triplets for carbon atoms C1 and C due to coupling to deuterium as expected for the alkene from (XII) but not from (XIII). In addition, the 2H 1H NMR spectrum shows approximately equal integration for deuterium at C1 and at C1 ... 

Recently, Alia et al.m studied Yp site-specific isotopically labelled with 2H, 13C and 170 by EPR. The hyperfine couplings and the spin density distribution at all ring positions of the radical were obtained. A strong H-bond to the protein was detected and the bond length estimated to 1.5 A. Isotope labelling has also been used earlier by Babcock s group (reviewed in reference 385). 

In 13C NMR spectra where CDCI3 solvent has been used, a triplet is observed because of the heteronuclear coupling between 13C and the deuterium atom 2H (D), which has a spin of 1 (Fig. 9.16). 

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