Monocyclic ß-Lactam: A Review on Synthesis and Potential Biological Activities of a Multitarget Core.

A monocyclic ring in their structure characterizes monobactams, a subclass of ß-lactam antibiotics. Many of these compounds have a bactericidal mechanism of action and acts as penicillin and cephalosporins, interfering with bacterial cell wall biosynthesis. The synthesis of novel ß-lactams is an emerging area of organic synthesis research due to the problem of increasing bacterial resistance to existing ß -lactam antibiotics, and, in this way, new compounds have been presented with several structural modifications, aiming to improve biological activities. Among the biological activities studied, the most outstanding are antibacterial, antitubercular, anticholesterolemic, anticancer, antiinflammatory, antiviral, and anti-enzymatic, among others. This review explores the vast number of works related to monocyclic ß-lactams, compounds of great importance in scientific research.

Remarkable Electronic Effect on the meso-Tetra(thienyl)porphyrins.

Complexes derived from meso-tetra(thienyl)porphyrins (TThP) and meso-tetra(pyridyl)porphyrin (TPyP) containing peripheral ruthenium complexes with general formulas {TPyP[RuCl(dppb)(5,5'-Mebipy)]4}(PF6)4, {TThP[RuCl(dppb)(5,5'-Mebipy)]4}(PF6)4, and {TThP-me-[RuCl(dppb)(5,5'-Mebipy)]4}(PF6)4 [5,5'-Mebipy = 5,5'-dimethyl-2,2'-bipyridine and dppb = 1,4-bis(diphenylphosphino)butane] were synthesized and characterized by spectroscopy techniques (1H- and 31P{1H}-NMR, IR, UV/vis, fluorescence, and electron paramagnetic resonance (EPR)), cyclic voltammetry, coulometry, molar conductivity, and elemental analysis. Voltammetry and UV/vis studies demonstrated differentiated electronic properties for ruthenium appended with TThP and TThP-me when compared to ruthenium appended with TPyP. The UV/vis analysis for the ruthenium complex derived from TThP and TThP-me, as well as the Soret and Q bands, characteristics of porphyrins, showed a band at 700 nm referring to the Ru → S electronic transition, and porphyrin TThP-me showed another band at 475 nm from the Ru-N transition. The attribution of these bands was confirmed by spectroelectrochemical analysis. Cyclic voltammetry analysis for the ruthenium complex derived from TPyP exhibited only an electrochemical process with E1/2 = 0.47 V assigned to the Ru(II)/Ru(III) redox pair (Fc/Fc+). On the other hand, two processes were observed for the ruthenium complexes derived from TThP and TThP-me, with E1/2 around 0.17 and 0.47 V, which were attributed to the formation of a mixed valence tetranuclear species containing Ru(II) and Ru(III) ions, showing that the peripheral groups are not oxidized at the same potential. Fluorescence spectroscopic experiments show the existence of a mixed state of emission in the supramolecular porphyrin moieties. The results suggest the formation of Ru(II)-Ru(III) mixed valence complexes when oxidation potential was applied around 0.17 V in the {TThP[RuCl(dppb)(5,5'-Mebipy)]4}(PF6)4 and {TThP-me-[RuCl(dppb)(5,5'-Mebipy)]4}(PF6)4 species.