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Experimental and computational methods have been used to examine the behavior of one-, two-, and three-bond 13C−1H spin-coupling constants (1 J CH, 2 J CH and 3 J CH, respectively) within the β-d-ribofuranosyl ring 1 that may be potentially affected by ring conformation. Ab initio molecular orbital (MO) calculations at the HF/6-31G* and MP2/6-31G* levels of theory were employed to assess the effect of ring conformation on molecular parameters (i.e., bond lengths, angles, and torsions) of β-d-ribofuranose (2) and methyl β-d-ribofuranoside (3), and these data were validated through comparison to corresponding parameters obtained by X-ray crystallography. The MO-derived structural data were subsequently used to compute 1 J CH, 2 J CH and 3 J CH values in 2 as a function of ring conformation. This predicted behavior was then tested experimentally through the measurement of J CH values in conformationally-rigid model compounds (aldopyranosides) containing 13C−1H coupling pathways similar to those found in specific conformers of 2 and was examined for consistency with previously-derived empirical rules correlating J CH with structure in carbohydrates. Available J CH data obtained on several biologically-important compounds containing β-d-ribofuranosyl rings have been interpreted in light of the new correlations with ring conformation.

2‘-Deoxyribonucleosides (2‘-deoxyadenosine (1), 2‘-deoxycytidine (2), thymidine (3)) singly enriched with 13C at C2‘ have been prepared and used to obtain one-, two-, and three-bond 13C−1H and 13C−13C spin-coupling constants involving C2‘. Coupling data are interpreted with assistance from complementary 3 J HH data (PSEUROT analysis), furanose structural parameters obtained from molecular orbital calculations, structure-coupling correlations found for J CH and J CC in carbohydrates, and calculated J values. Spin couplings in 1−3 involving C1‘ and C2‘ are also compared to corresponding values in ribonucleosides in order to assess the effects of nucleoside structure and conformation on J values within the furanose ring. 1 J C2 ‘ ,H2 ‘ R and 1 J C2 ‘ ,H2 ‘ S in 1−3 and 1 J C2 ‘ ,H2 ‘ in ribonucleosides depend on C−H bond orientation; 1 J C1 ‘ ,H1 ‘ in 1−3 and in ribonucleosides exhibits a similar dependence. The latter couplings appear to be essentially unaffected by N-glycoside torsion. 1 J CC values depend on the number and distribution of electronegative substituents on the C−C fragment. A modified projection curve is proposed to aid in the interpretation of 2 J C2 ‘ ,H1 ‘ values; the presence of N substitution at C1‘ causes a shift to more negative couplings relative to the O-substituted analog. In contrast, 2 J C1 ‘ ,H2 ‘ is essentially unaffected by the same change in the electronegative substituent at C1‘. 2 J CC values within the furanose ring are determined by two coupling pathways; in one case (i.e., 2 J C1 ‘ ,C3 ‘), the observed coupling is shown to be the algebraic sum of the two couplings arising from each pathway. 3 J CH and 3 J CC values depend in general on appropriate molecular dihedral angles as expected (Karplus relationships); however, 3 J C2 ‘ ,H4 ‘ values exhibit unexpected behavior, thus suggesting potential limitations in its use as a structural probe.

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