Synthesis and Characterization of Ruthenium and Rhenium Nucleosides

Diastereomeric Separation of Chiral fac-Tricarbonyl(iminopyridine) Rhenium(I) Complexes and Their Cytotoxicity Studies: Approach toward an Action Mechanism against Glioblastoma

A series of new (tricarbonyl)rhenium(I) complexes were synthesized using chiral bidentate ligands (+)/(-)-iminopyridines (L_R/L_S). The reaction yielded a mixture of mononuclear Re(I) diastereoisomers, formulated as fac-[Br(CO)₃Re_(S/R)L_(S/R)]. Each single diastereoisomer was isolated and fully characterized. X-ray crystallography and circular dichroism spectra verified their enantiomeric nature. The cytotoxicity of each complex was evaluated against six cancer cell lines. The effect of the two complexes on viability, proliferation, and migration was analyzed on glioblastoma cell lines (U251 and LN229). Changes in the expression of histones, apoptotic, and key signaling proteins, as well as alterations in DNA structure, were also observed. These experiments showed that the chirality associated with both metal and ligand has a strong influence on cytotoxicity.

The folding of a metallopeptide

We have applied solid-phase synthesis methods for the construction of tris(bipyridyl) peptidic ligands that coordinate Fe(ii) ions with high affinity and fold into stable mononuclear metallopeptides. The main factors influencing the folding pathway and chiral control of the peptidic ligands around the metal ions have been studied both by experimental techniques (CD, UV-vis and NMR) and molecular modeling tools. Amongst the numerous molecular variables that have been studied, this study clearly illustrates how the chirality of a given set of aminoacids (proline in this case) of the peptide dictates the chirality of the metal center of the resulting metallopeptide. Moreover, the relatively hydrophobic peptidic models used in this work show that the most stable structures present reduced solvent contacts and, in counterpart, stabilize the cis configuration of the proline residues.

Metallamacrocycle formation through dimerization of metal bioconjugates derived from amino acids and peptides

Metallamacrocycles of 12, 16, and 22 members are obtained by deprotonation of the carboxylic group of the side chain of iminopyridine complexes derived from the amino acid β-alanine, and the peptides Gly-Gly and Gly-Gly-Gly. Instead of the expected intramolecular attack to give tridentate (N,N,O) ligands, the deprotonated carboxylate attacks in an inter-molecular manner to give dimers in which the ligand acts as a bridge bonded in a κ(2)(N,N') chelating fashion to one metal and as κ(O) to the other metal. The formation of the dimers is supported by NMR spectroscopy, mass spectrometry and X-ray crystallography.