Distortionless enhancement carbon resonance assignment

The 13C chemical shifts were assigned in more detail for monosulfidic and polysulfidic crosslinks occurring in the accelerated sulfur vulcanisation of NR [18]. The NR was cured with a pure thiuram formulation (TMTD alone) in order to predominantly prepare monosulfidic bridges in the network. The distortionless enhancement by polarisation transfer (DEPT) experiments, in which the carbons with different level of protonation can be distinguished [22-24], were performed for the NR cured with extended levels of sulfur. Based on the DEPT results and previously reported model compound results [20], the chemical shifts of the resonances occurring in the spectra were assigned. 

HSQC) or heteronuclear multiple quantum correlation (HMQC). The combined experiments such as 2D HSQC(HMQC)-TOCSY experiments are powerful tools for the assignment of the 13C and 11 resonances belonging to the same sugar residue providing enhanced dispersion of TOCSY correlations in the carbon dimension. More recendy, different carbon multiplicity editing methods, for example, DEPT (distortionless enhanced polarization transfer)-HMQC and E-HSQC, have been developed to reduce the complexity of proton-carbon correlation spectra and to enhance the resolution by narrowing the applied spectral window.11... 

The proton-decoupled 13C NMR spectrum of pergolide mesylate indicates the presence of twenty carbons, which are further identified as four non-protonated carbons, six methine carbons, and ten methyl and methylene carbons via a Distortionless Enhancement by Polarization Transfer (DEPT) spectrum. The eight aromatic and olefinic carbon resonances in the 134 ppm to 106 ppm region have chemical shifts consistent with an indole structure (2). The H NMR spectrum contains four aromatic proton resonances, from 6.88 to 7.22 ppm, whose chemical shifts are also indicative of an indole-type structure. The assignment of these carbon and proton resonances were confirmed with IH correlation spectroscopy (CDSY) and 3C-1H heteronuclear correlation spectroscopy (HETCORR). The UV spectrum also indicates the presence of an indole chromophore. 

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