Chemical Shift Tensors in Isomers of Adenine: Relation to Aromaticity of Purine Rings?

Abstract

The (13)C and (15)N chemical shift tensors are measured, calculated, and compared for three N-benzyladenine isomers with an attempt to characterize differences in electron distribution in the purine ring related to the position of the substituent. Furthermore, the aromaticity of the purine rings is evaluated on the basis of nucleus-independent chemical shifts, and variations among the isomers are discussed. Both parameters indicate significant differences between the electronic properties of the N3-substituted compound and the N7/N9 pair of structures, which can be viewed more generally as the reason for the different stabilities of the individual tautomers.

Geometric and energetic consequences of prototropy for adenine and its structural models – a review

“…p-Electrons seem to be less delocalized for many CHs and CH-NHs than for p-p conjugated 1,3-butadiene {HOMED 0.627 (ref. 152 Some deformability of the purine ring and no planarity of the exo NH 2 group have been also reported for adenine. 141 This is the main reason, for which the rHOMA indices for many CHs are negative, and do not describe well p-electron delocalization.…”

“…133,143,144,[148][149][150][151] For its N-benzyl derivatives, aromaticity was studied for major amine tautomers. 152 Some deformability of the purine ring and no planarity of the exo NH 2 group have been also reported for adenine. 121,127 One-electron oxidation and one-electron reduction change the HOMED indices for all tautomers in different ways (in some cases even by more than 0.2 units), but do not change the general tendency that the NH and NH-NH tautomers are more delocalized than the CH and CH-NH ones.…”

Solvent‐directed Regioselective Benzylation of Adenine: Characterization of N9‐benzyladenine and N3‐benzyladenine

“…mp: 279–281°C, (lit. 280–281°C). IR (KBr, cm −1 ): 3319, 3099, 1658, 1617, 1567, 1455, 1405, 1226, 1176, 1014, 656.…”

Solid-state NMR studies of nucleic acid components

“…63 The principal components of 13 C and 15 N chemical-shi tensors in solid 3-, 7-, and 9-benzyladenine isomers have been determined and the inuence of the substitution on the magnitude and orientation of the tensors has been discussed. 64 Several isotopes can be utilised as probes for measuring dynamics in the solid state. One of the most useful isotopes is deuterium, because the solid-state NMR line shape and relaxation of deuterium spins are essentially dominated by a single mechanismthe interaction of the nuclear quadrupole moment with local electric eld gradients.…”