(1'-C-13)-2'-DEOXYRIBONUCLEOSIDES - STRUCTURAL AND CONFORMATIONAL INSIGHTS DERIVED FROM C-13-H-1 SPIN COUPLING-CONSTANTS INVOLVING C1'

2'-Deoxyadenosine (1), 2-deoxycytidine (2), and thymidine (3) have been prepared with C-13-enrichment at C1'(99 atom% C-13) and studied by H-1 NMR spectroscopy at 500 MHz in (H2O)-H-2. 1J(CH), 2J(CH) and 3J(CH) values were measured between C1' and several protons in the furanose and base moieties of 1-3 and compared to related values observed in corresponding ribonucleosides and erythronucleosides. Results are consistent with the expected shift to south conformers on conversion of ribonucleosides to 2'-deoxyribonucleosides. The observation that Cl' of 1-3 couples more strongly to H2'S (approximately 5.7 Hz) than to H2'R (less-than-or-equal-to 0.4 Hz) has been explained using model compounds that mimic the Cl'-C2-H2'R and C1'-C2'-H2'S coupling pathways in pure north and south conformers of 1-3. Results suggest that the difference, \2J(C1',H2'S\ - \2J(C1',H2'R)\ may be a useful probe of N/S equilibria in 2'-deoxyribonucleosides in (H2O)-H-2 solution. Model compounds have also been used to probe the effect of ring conformation on the chemical shifts of H2'R and H2'S in 1-3. For simple, unphosphorylated 2-deoxy-beta-D-ribofuranosyl rings in aqueous solution, the difference, delta(H2'R) - delta(H2'S), may be correlated with N/S distribution.