Assignment of the Pyrimidine Resonances

Some of the common pyrimidine nucleosides are symbolized by the following formula  

Methods similar to those mentioned above have been used for the signal identification of the pyrimidine resonances [428, 735, 749, 757, 760, 765] (cf. Table 5.22). 

Comparison of the spectrum of uridine with data of 4-thiouridine, 2,4-dithiouridine, thymidine, 4-thiothymidine, cytidine and 2-thiocytidine allows the assignment of all carbon resonances of these pyrimidine moieties. Further confirmation of these assignments is obtained from the proton off-resonance decoupled 13C-spectra of these nucleosides, as has been demonstrated for thymidine The pyrimidine CH3 and CH resonances of the proton broadband-decoupled spectrum are split into a quartet and a doublet, respectively, in the proton off-resonance spectrum, and can thus be easily assigned. 

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