Half-sandwich d 6 metal complexes comprising of 2-substituted-1,8-napthyridine ligands with unexpected bonding modes: Synthesis, structural and anti-cancer studies

Synthesis of 2-(Pyridin-2-yl)phenols and 2-(Pyridin-2-yl)anilines

Herein, we report a new synthetic strategy for 2-(pyridin-2-yl)phenols and 2-(pyridin-2-yl)anilines catalyzed by a Pd/C-ethylene system. The starting materials, 2-(pyridin-2-yl)cyclohexan-1-ones, can be easily prepared by the reaction of substituted pyridine N-oxide and cyclohexanones. The most useful feature of this method is that both 2-(pyridin-2-yl)phenols and 2-(pyridin-2-yl)anilines are easily synthesized independently using the same compound as a starting material, simply by adding or not adding a nitrogen source.

Friedlӓnder's synthesis of quinolines as a pivotal step in the development of bioactive heterocyclic derivatives in the current era of medicinal chemistry

In the current scenario of medicinal chemistry, quinoline plays a pivotal role in the design of new heterocyclic compounds with several pharmacological properties, so the search for new synthetic methodologies and their application in drug discovery has been widely studied. So far, many procedures have been performed for the preparation of quinoline scaffolds, among which Friedländer quinoline synthesis plays an important role in obtaining these heterocycles. The Friedländer reaction involves condensation between 2-aminobenzaldehydes and keto-compounds. The quinoline nucleus, once obtained through the Friedländer synthesis, has been extensively modified so that these derivatives can exhibit a large number of biological activities such as anticancer, antimalarial, antimicrobial, antifungal, antituberculosis, and antileishmanial properties. In this work, the focus is on the applicability of the Friedländer reaction in the synthesis of various types of bioactive heterocyclic quinoline compounds, which to date has not been reported in the context of medicinal chemistry. The main part of this review selectively focuses on research from 2010 to date and will present highlights of the Friedländer quinoline synthesis procedures and findings to address biological and pharmacological activities.

Anticancer Half-Sandwich Rhodium(III) Complexes

Platinum-based anticancer drugs are most likely the most successful group of bioinorganic compounds. Their apparent disadvantages have led to the development of anticancer compounds of other noble metals, resulting in several ruthenium-based drugs which have entered clinical trials on oncological patients. Besides ruthenium, numerous rhodium complexes have been recently reported as highly potent antiproliferative agents against various human cancer cells, making them potential alternatives to Pt- and Ru-based metallodrugs. In this review, half-sandwich Rh(III) complexes are overviewed. Many representatives show higher in vitro potency than and different mechanisms of action (MoA) from the conventional anticancer metallodrugs (cisplatin in most cases) or clinically studied Ru drug candidates. Furthermore, some of the reviewed Rh(III) arenyl complexes are also anticancer in vivo. Pioneer anticancer organorhodium compounds as well as the recent advances in the field are discussed properly, and adequate attention is paid to their anticancer activity, solution behaviour and various processes connected with their MoA. In summary, this work summarizes the types of compounds and the most important biological results obtained in the field of anticancer half-sandwich Rh complexes.

Effect of N,N Coordination and RuII Halide Bond in Enhancing Selective Toxicity of a Tyramine-Based RuII (p-Cymene) Complex

Ruthenium compounds are promising anticancer candidates owing to their lower side-effects and encouraging activities against resistant tumors. Half-sandwich piano-stool type Ru^II compounds of general formula [(L)Ru^II(η⁶-arene)(X)]⁺ (L = chelating bidentate ligand, X = halide) have exhibited significant therapeutic potential against cisplatin-resistant tumor cell lines. In Ru^II (p-cymene) based complexes, the change of the halide leaving group has led to several interesting features, viz., hydrolytic stability, resistance toward thiols, and alteration in pathways of action. Tyramine is a naturally occurring monoamine which acts as a catecholamine precursor in humans. We synthesized a family of N,N and N,O coordinated Ru^II (p-cymene) complexes, [(L)Ru^II(η⁶-arene)(X)]⁺ (1-4), with tyramine and varied the halide (X = Cl, I) to investigate the difference in reactivity. Our studies showed that complex 2 bearing N,N coordination with an iodido leaving group shows selective in vitro cytotoxicity against the pancreatic cancer cell line MIA PaCa-2 (IC₅₀ ca. 5 μM) but is less toxic to triple-negative breast cancer (MDA-MB-231), hepatocellular carcinoma (Hep G2), and the normal human foreskin fibroblasts (HFF-1). Complex 2 displays stability toward hydrolysis and does not bind with glutathione, as confirmed by ¹H NMR and ESI-HRMS experiments. The inert nature of 2 leads to enhancement of cytotoxicity (IC₅₀ = 5.3 ± 1 μM) upon increasing the cellular treatment time from 48 to 72 h.

Developments in Platinum-Group Metals as Dual Antibacterial and Anticancer Agents

Platinum-group (PG) complexes have been used as antibacterial and anticancer agents since the discovery of cisplatin. The science world still requires improvement on these complexes because of multidrug and antineoplastic resistances. This review observes discoverers and history of these platinum-group metals (PGMs), as well as their beneficial applications. The focus of this study was biological applications of PGMs in relation to human health. Sandwich and half-sandwich PGM coordination compounds and their metal nanoparticles give improved results for biological activities by enhancing efficient delivery of both antibacterial and anticancer drugs, as well as luminescent bioimaging (biomarkers) for biological identifications.