Synthetic, Structural, and Anticancer Activity Evaluation Studies on Novel Pyrazolylnucleosides

Yadav, Yogesh; Sharma, Deepti; Kaushik, Kumar; Kumar, Vineet; Jha, Amitabh; Prasad, Ashok K.; Len, Christophe; Malhotra, Sanjay V.; Wengel, Jesper; Parmar, Virinder S.

Ar-Bearing C Shifts in the 13 Table 2 . Chemical shift and coupling constants from the 1 H-NMR of compounds 3d, 4d, 5d, and 6d in acetone-d 6 . a Please refer to structures in Table 4 for skeleton numbering. Table 2 were all measured in acetone-d 6 (on an Bruker Avance 400 instrument) and may therefore differ from those in Table 1 , which were measured in CDCl 3 (on Bruker Avance 300 instrument). * Due to the spatial interactions between different protons as explicitly shown in Table 4 , these protons exhibited multiplicities as shown here when the spectra were recorded in acetone-d 6 on a Bruker Avance 400 instrument as against those recorded in CDCl 3 , CD 3 CN or DMSO-d 6 as given in the Experimental section for the corresponding protons where they appeared as broad singlets or ill resolved multiplets when their spectra were recorded on a Bruker Avance 300 instrument. Table 3 were all measured in acetone-d 6 (on an Bruker Avance 400 instrument) and may therefore differ from those in Table 1 , which were measured in CDCl 3 (on Bruker Avance 300 instrument). In order to confirm the above positional assignments, we performed 2D NMR experiments (NOESY and HMBC) on the two pairs of compounds (i.e., one pair consisting of the ditoluoyl protected nucleosides 3d and 4d and another pair consisting of the deprotected nucleosides 5d and 6d) ( Table 4 ). The results of the HMBC experiments rely on the fact that the anomeric proton may see the aryl bearing pyrazole carbon in 3d and 5d, but not in 4d and 6d, while the NOESY results would explain the spatial proximity of the anomeric proton to either the protons in the -CH 2 CN group or to the ortho protons of the aryl group. Our results verified the positional properties at the pyrazole ring in the four compounds and are summarized in Table 4 .