Intramolecular interactions in acyclic and macrocyclic compounds containing nucleotide bases

Novel macrocyclic uracil derivatives: Structure in solid and solution

“…The synthesized compounds were studied optically at concentrations low enough to preclude formation of intermolecular complexes so that the interactions of the bases could be characterized by ultraviolet [14]. According to the theories of Tinoco [15] and Rhodes [16], depending on the relative orientation of the transition moments, hypochromism (parallel stacking of the chromophores) or hyperchromism (linear array of the chromophores) is observed.…”

“…It proves that the geometry of the macrocyle is the same both in apolar solutions and in polar solutions. It is possible that the length of the bridge is too large to allow attractive interactions between uracil units mediated by water [14,19].…”

Synthesis and structures of pyrimidinophanes containing a nitrogen atom in the bridge

“…Analysis for the macrocycle was performed analogously. The 2D HMBC spectrum of 5, unlike the spectrum of pyrimidinophane 4, shows additional cross peaks between the CH 3 group and C(14), C (16), and C(2)H and NOE between C(2)H and C(16)H. Therefore, the geminal protons of the CH 2 groups at N (13) and N(1) of pyrimidinophanes 4 and 5 are essen tially nonequivalent. The magnetic nonequivalence of these protons is a consequence of conformational rigidity of the pyrimidinophane molecules, on the one hand, and the anisotropy of the pyrimidine ring, on the other hand.…”

“…In pyrimidinophane 4, the intensity of the ion corresponding to the loss of the methyl group from the molecular ion is 80.7%; in com pound 5, only 4.8%. This result can be attributed to the influence of the N(1) pyr atom, which is responsible for the cleavage of the β bond with respect to the N(1)-C (16) bond. In this case, the positive charge is localized on the nitrogen atom to form a conjugated bond system in the [M -Me] + ion.…”

α,ω-Bis(3,6-dimethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-yl)alkanes and products of their cyclization, pyrimidinophanes: intra- and intermolecular interaction in crystals and in solutions

“…Such an approach can be highly informative when applied toward the subjects in question, which has been demonstrated by the comparison of the NMR and UV spectroscopy data for 1,4 bis(pyrimidin 1 yl)butane (1b) with those for the synthesized on its basis pyrimidinophane 2b. 12 Geometry and crystal packing of compounds 1 and 2 in the crystal are also of interest. As it was mentioned above, there are virtually no X ray literature data on the mutual position of the 1,3 dialkyl substituted uracil de rivatives in the crystal.…”