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Abstract
The intra- and intermolecular hydrogen bonding (ΔGº298K ≈ 2, kcal mol−1) of 2′-OH in nucleos(t)ides has been reported by the temperature- and concentration-dependent NMR study in conjunction with dihedral dependence of the NMR derived both endo (3 J H,H)- and exocyclic (3 JH,OH) coupling constants, nOe contacts and lineshape analyses of hydroxyl protons for EtpA (1), 3′-dA (2), rA (3), 2′-dA (4) [Fig. ] in DMSO-d 6 at 500 MHz.
Figure 1. The schematic representation of the bias of the dymanic two-state pseudorotational equilibrium between the North-type (N, C2′-exo -C3′-endo) and the South-type (S, C3′-exo-C2′-endo) Citation[3a] pseudorotamers of the sugar moeity for EtpA (1), 3′-dA (2), rA (3), 2′-dA (4) and torsion (Φ) around C2′/3′-O bond viz. Φ1 = ΦH2′‒C2′‒O‒H and Φ2 = ΦH3′‒C3′‒O‒H except in 1 where the torsion across C3′-O3′ bond is actually ϵ− [C4′-C3′-O3′-P].
![Figure 1. The schematic representation of the bias of the dymanic two-state pseudorotational equilibrium between the North-type (N, C2′-exo -C3′-endo) and the South-type (S, C3′-exo-C2′-endo) Citation[3a] pseudorotamers of the sugar moeity for EtpA (1), 3′-dA (2), rA (3), 2′-dA (4) and torsion (Φ) around C2′/3′-O bond viz. Φ1 = ΦH2′‒C2′‒O‒H and Φ2 = ΦH3′‒C3′‒O‒H except in 1 where the torsion across C3′-O3′ bond is actually ϵ− [C4′-C3′-O3′-P].](/cms/asset/9793bb15-0884-483c-a9ae-a8cb4d7a864b/lncn_a_10347008_o_f0001.gif)
ACKNOWLEDGEMENTS
We thank the Swedish Board for Technical Development (TFR), the Swedish Natural Science Research Council (NFR), and the Swedish Board for Technical Development (NUTEK) for generous financial support. Thanks are due to the Wallenbergstiftelsen, ForskningsraÊ dsnämnden and the University of Uppsala for funds to purchase of 500-MHz and 600-MHz Bruker DRX NMR spectrometers.