Synthesis and complementary self-association of novel lipophilic π-conjugated nucleoside oligomers

Abstract

Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: A series of lipophilic nucleosides comprising natural and non-natural bases that are -conjugated to a short oligophenylene-ethynylene fragment has been synthesized. These bases comprise guanosine, isoguanosine, 2-aminoadenosine as purine heterocycles, and cytidine, isocytosine and uridine as complementary pyrimidine bases. The hydrogen-bonding dimerization and association processes between complementary bases were as well studied by 1 H NMR and absorption spectroscopies in order to obtain the relevant association constants.

Role of the Symmetry of Multipoint Hydrogen Bonding on Chelate Cooperativity in Supramolecular Macrocyclization Processes

“…in CHCl 3 . [12] This can be explained by the different stabilizing/destabilizing secondary H-bonding interactions between vicinal donor and acceptor groups in the DAD-ADA (A:U) pair versus the DDA-ADD (G:C or iG:iC) pair. [9] However, the experimental results obtained in this work and exposed in Table 1, suggest that such reduction is actually much larger.…”

“…a Determined from titration experiments with the mononucleosides: G+C, iG+iC, A+U. [12] Data calculated from: b 1 H NMR dilution ( Figure S9). c UV-vis dilution ( Figure S13).…”

“…As a matter of fact, the EM of the system can be inversely related to the competition equilibrium constant (K C ) as: EM = 1/K C . [11] The EM values for each cyclotetramerization process (Table 1) [10,12] using the relationship:…”

Synthesis of 5‐/8‐Halogenated or Ethynylated Lipophilic Nucleobases as Potential Synthetic Intermediates for Supramolec­ular Chemistry

“…As opposed to related nucleosides, [8] where the bulky ribose unit attached at these position limits aggregation, these simple and planar groups may help in producing hierarchical assemblies where hydrogenbonding is combined with other non-covalent interactions acting in orthogonal directions, such as π-π stacking with other molecules or with planar substrates.…”

“…[6] For these reasons, the development of efficient and reliable synthetic routes to modified nucleobases as versatile building blocks in selfassembly can be of great importance and utility to the supramolecular chemist. [7], [8] Here, we describe the synthesis of a series of chemicallymodified lipophilic natural and non-natural nucleobase derivatives ( Figure 1) that are equipped with either an halogen atom or an ethynyl group at the 5-position (for the pyrimidines) or at the 8-position (in the case of the purines). Pyrimidine nucleobases comprise cytosine (C), uridine (U), and isocytosine (iC), whereas the purines prepared in this work are guanine (G), 2,6-diaminopurine or 2-aminoadenine (DAP; hereafter abbreviated as A), and isoguanine (iG).…”