Search

To gain insights into the activity of metal‐based drugs against SARS‐CoV‐2, five rhenium complexes, namely fac‐[Re(CO)3(acac)(PPh2Cy)] (I), fac‐[Re(CO)3(acac)(PPhCy2)] (II), fac‐[Re(CO)3(acac)(PCy3)] (III), fac‐[Re(CO)3(acac)(P(m‐tolyl)3)] (IV), and fac‐[Re(CO)3(acac)(P(p‐tolyl)3)] (V), with acac=acetylacetonato, PPh2Cy=cyclohexyldiphenylphosphine, PPhCy2=dicyclohexylphenylphosphine, PCy3=tricyclohexylphosphine, P(m‐tolyl)3=tri(m‐tolyl)phosphine, and P(p‐tolyl)3=tri(p‐tolyl)phosphine, were docked in the binding pockets of main protease, spike glycoprotein, and RNA‐dependent RNA polymerase. The resulting binding sites revealed potent SARS‐CoV‐2 inhibition, resulting from the formation of classical N−H⋅⋅⋅O and O−H⋅⋅⋅O hydrogen bonds, carbon C−H⋅⋅⋅O H‐bonds, hydrophobic contacts, as well as non‐conventional interactions such as weak C−H⋅⋅⋅N interactions, H⋅⋅⋅H, C⋅⋅⋅H/H⋅⋅⋅C, C⋅⋅⋅lp/lp⋅⋅⋅C and lp⋅⋅⋅lp contacts, cation‐π interactions and π⋅⋅⋅π stacking in the targets' binding pockets. Moreover, we have optimized the molecular structures of these compounds using DFT methods and correlated them correspondingly to their crystal structures. We have estimated and evaluated the associated frontier molecular orbitals, as well as the global reactivity descriptors for which we have discussed the compounds' reactivity. We have also examined intermolecular interactions by carrying out a Hirshfeld surface (HS) analysis, which showed the presence of C−H⋅⋅⋅H−C, C−H⋅⋅⋅C interactions, C−H⋅⋅⋅O non‐classical hydrogen bonds and π⋅⋅⋅π stacking, as well as non‐conventional π⋅⋅⋅lp and lp⋅⋅⋅lp interactions. [ABSTRACT FROM AUTHOR]

Two rhenium complexes, namely, fac‐tricarbonyl(triphenylphosphane‐κP)(tropolonato‐κ2O,O′)rhenium(I), [Re(C7H5O2)(C18H15P)(CO)3] or fac‐[Re(Trop)(PPh3)(CO)3] (1), and fac‐tricarbonyl(3,5,7‐tribromotropolonato‐κ2O,O′)(triphenylphosphane‐κP)rhenium(I), [Re(C7H2Br3O2)(C18H15P)(CO)3] or fac‐[Re(TropBr3)(PPh3)(CO)3] (2) (TropH is tropolone and and TropBr3H is tribromotropolone), were synthesized and their crystal and molecular structures confirmed by single‐crystal X‐ray diffraction. Both crystallized in the space group P and display an array of inter‐ and intramolecular interactions which were confirmed by solid‐state 13C NMR spectroscopy using cross polarization magic angle spinning (CPMAS) techniques, as well as Hirshfeld surface analysis. The slightly longer Re—P distance of 1 [2.4987 (5) versus 2.4799 (11) Å for 1 and 2, respectively] suggests stronger back donation from the carbonyl groups in the former case, possibly due to the stronger electron‐donating ability of the unsubstituted tropolonate ring system. However, this is not supported in the Re—CO bond distances of 1 and 2. [ABSTRACT FROM AUTHOR]

Two bidentate PNP ligands N,N-bis(di-p-tolylphosphino)cyclohexylamine (Cy-pTolPNP) (1) and N,N-bis(di-p-tolylphosphino)cyclobutylamine (Cb-pTolPNP) (2) were synthesized and crystallized. Coordination to the fac-[MI(CO)3]+ core (M = Re, 99Tc) yielded fac-[Re(Cy-pTolPNP)(CO)3Br] (1A), fac-[99Tc(Cy-pTolPNP)(CO)3Cl] (1B), fac-[Re(Cb-pTolPNP)(CO)3Br] (2A) and fac-[99Tc(Cb-pTolPNP)(CO)3Cl] (2B) in relatively good yields (56 to 86%): The structures of 1, 2, 1A and 1B were studied by single crystal X-ray crystallography. Preliminary mitochondrial/antimicrobial evaluation of the free ligand (N,N-bis(di-p-tolylphosphino)-cyclohexylamine) (1) and its respective fac-[Re(CO)3]+ (1A) complex indicates that neither the free ligand nor the complex was active against selected fungi Eremothecium ashbyii and Nadsonia fulvescens. In addition, all four compounds were found to have no activity against Gram-positive and Gram-negative bacterial species. These biological results are essential to the understanding of how these types of complexes behave and show they are perfectly stable in the evaluated bio-environments. The results also indicate that these ligands and complexes may present themselves as excellent models for radiotoxicity studies using technetium-99m, but more specifically, rhenium Re-186 and Re-188. [ABSTRACT FROM AUTHOR]

Gamma-aminobutyric acid (GABA) signaling is the principal inhibitory pathway in the central nervous system. It is critical in neuronal cell proliferation and fate determination. Any aberration in GABA inhibition results in psychiatric and neurological diseases. Thus, modulating GABAergic neurotransmission has become the basis of drug therapy for psychiatric and several neurological diseases. Though GABA and muscimol are classical inhibitors of GABA receptors, the search for novel inhibitors continues unabated. In this study, the binding mechanism of GABA and muscimol was elucidated and applied in the search for small molecule GABAergic inhibitors using comprehensive computational techniques. It was revealed that a high-affinity binding of GABA and muscimol was mediated by a water molecule involving α 1 Thr129 and then stabilized by strong interactions including salt bridges with β 2 Glu155 and α 1 Arg66 amidst hydrogen bonds, π-π stacking, and π -cation interactions with other residues. The binding of GABA and muscimol was also characterized by stability and deeper penetration into the hydrophobic core of the protein which resulted in conformational changes of the binding pocket and domain, by inducing correlated motions of the residues. Thermodynamics analysis showed GABA and muscimol exhibited total binding free energies of -19.85 ± 8.83 Kcal/mol and -26.55 ± 3.42 Kcal/mol, respectively. A pharmacophore model search, based on the energy contributions of implicating binding residues, resulted in the identification of ZINC68604167, ZINC19735138, ZINC04202466, ZINC00901626, and ZINC01532854 as potential GABA-mimetic compounds from metabolites and natural products libraries. This study has elucidated the binding mechanisms of GABA and muscimol and successfully applied in the identification of GABA-mimetic compounds.Communicated by Ramaswamy H. Sarma.

Two rhenium complexes, namely, fac-tricarbonyl(triphenylphosphane-κP)(tropolonato-κ 2 O,O')rhenium(I), [Re(C 7 H 5 O 2 )(C 18 H 15 P)(CO) 3 ] or fac-[Re(Trop)(PPh 3 )(CO) 3 ] (1), and fac-tricarbonyl(3,5,7-tribromotropolonato-κ 2 O,O')(triphenylphosphane-κP)rhenium(I), [Re(C 7 H 2 Br 3 O 2 )(C 18 H 15 P)(CO) 3 ] or fac-[Re(TropBr 3 )(PPh 3 )(CO) 3 ] (2) (TropH is tropolone and and TropBr 3 H is tribromotropolone), were synthesized and their crystal and molecular structures confirmed by single-crystal X-ray diffraction. Both crystallized in the space group P-1 and display an array of inter- and intramolecular interactions which were confirmed by solid-state 13 C NMR spectroscopy using cross polarization magic angle spinning (CPMAS) techniques, as well as Hirshfeld surface analysis. The slightly longer Re-P distance of 1 [2.4987 (5) versus 2.4799 (11) Å for 1 and 2, respectively] suggests stronger back donation from the carbonyl groups in the former case, possibly due to the stronger electron-donating ability of the unsubstituted tropolonate ring system. However, this is not supported in the Re-CO bond distances of 1 and 2., (open access.)