Abstract2′‐Deoxyadenosine, 2′‐deoxycytidine, 2′‐deoxyguanosine and 2′‐deoxyuridine were prepared with stereoselective deuteriation at C‐5′ and used to assign the prochiral C‐5′ protons in 300 MHz1H NMR spectra obtained in2H2O. In all cases, the more shielded C‐5′ proton was found to be the pro‐Rproton. From these assignments, C‐4′–C‐5′ rotamer populations were determined using three previously published methods based on the spin couplings,3J(H‐4′,H‐5′R) and3J(H‐4′,H‐5′S), and the errors associated with these methods were assessed. The effects of base structure, furanose andN‐glycoside bond conformation on the relative populatio