15N and 13C NMR chemical shifts of 6-(fluoro, chloro, bromo, and iodo)purine 2'-deoxynucleosides: measurements and calculations.

The (15)N and (13)C chemical shifts of 6-(fluoro, chloro, bromo, and iodo)purine 2'-deoxynucleoside derivatives in deuterated chloroform were measured. The (15)N chemical shifts were determined by the (1)H-(15)N HMBC method, and complete (15)N chemical-shift assignments were made with the aid of density functional theory (DFT) calculations. Inclusion of solvation effects significantly improved the precision of the calculations of (15)N chemical shifts. Halogen-substitution effects on the (15)N and (13)C chemical shifts of purine rings are discussed in the context of DFT results. The experimental coupling constants for (19)F interacting with (15)N and (13)C of the 6-fluoropurine 2-deoxynuleoside are compared with those from DFT calculations.