Regioselective Synthesis of 2,5-Disubstituted-1,3,4-thiadiazoles and 1,3,4-Oxadiazoles via Alkyl 2-(Methylthio)-2-thioxoacetates and Alkyl 2-Amino-2-thioxoacetates

An acid-catalyzed regioselective cyclization reaction of 2,5-disubstituted-1,3,4-thiadiazoles and 1,3,4-oxadiazoles has been developed. The synthetic precursors alkyl 2-(methylthio)-2-thioxoacetates/alkyl 2-amino-2-thioxoacetates react efficiently with acyl hydrazides, which transformed into a series of dehydrative and desulfurative products with employment of p-TSA and AcOH through a regioselective cyclization process. The alkyl 2-amino-2-thioxoacetate pathway generates excellent yield among the mentioned procedures. The reported methods are operationally simplistic and highly efficient with metal-free conditions and demonstrate significant functional group compatibility. Regioselective cyclized products were confirmed by single-crystal X-ray diffraction studies.

Adenine Modification at C7 as a Viable Strategy to Potentiate the Antimalarial Activity of Quinolones

Although many quinolones have shown promise as potent antimalarials, their clinical development has been slow due to poor performance in vivo. Insights into structural modifications that can improve their therapeutic potential will be very valuable in this vibrant area of research. Our studies involving a library of quinolones which vary in substitution pattern at N1, C3, C6 and C7 positions have shown that the presence of adenine moiety at C7 can bring a noticeable improvement in activity compared to other heterocyclic groups at this location. The most potent compound emerged from this study showed IC₅₀ values of 0.38 μM and 0.75 μM against chloroquine-sensitive and -resistant (W2) strains, respectively. Docking analysis in the Q_o site of cytochrome bc1 complex revealed the contribution of a key H-bonding interaction from the adenine unit in target binding. This corroborates with compound-induced loss of mitochondrial functions. These findings not only open avenues for further exploration of antimalarial potential of adenine-modified quinolones, but also suggests broader opportunities during lead-optimization against other antimalarial targets.

Antiplasmodial and antimalarial activities of quinolone derivatives: An overview

Malaria remains one of the most deadly infectious diseases globally. Considering the growing spread of resistance, development of new and effective antimalarials remains an urgent priority. Quinolones, which are emerged as one of the most important class of antibiotics in the treatment of various bacterial infections, showed potential in vitro antiplasmodial and in vivo antimalarial activities, making them promising candidates for the chemoprophylaxis and treatment of malaria. This review presents the current progresses and applications of quinolone-based derivatives as potential antimalarials to pave the way for the development of new antimalarials.

Small molecule-based inhibition of MEK1/2 proteins dampens inflammatory responses to malaria, reduces parasite load, and mitigates pathogenic outcomes

Malaria infections cause several systemic and severe single- or multi-organ pathologies, killing hundreds of thousands of people annually. Considering the existing widespread resistance of malaria parasites to anti-parasitic drugs and their high propensity to develop drug resistance, alternative strategies are required to manage malaria infections. Because malaria is a host immune response-driven disease, one approach is based on gaining a detailed understanding of the molecular and cellular processes that modulate malaria-induced innate and adaptive immune responses. Here, using a mouse cerebral malaria model and small-molecule inhibitors, we demonstrate that inhibiting MEK1/2, the upstream kinases of ERK1/2 signaling, alters multifactorial components of the innate and adaptive immune responses, controls parasitemia, and blocks pathogenesis. Specifically, MEK1/2 inhibitor treatment up-regulated B1 cell expansion, IgM production, phagocytic receptor expression, and phagocytic activity, enhancing parasite clearance by macrophages and neutrophils. Further, the MEK1/2 inhibitor treatment down-regulated pathogenic pro-inflammatory and helper T cell 1 (Th1) responses and up-regulated beneficial anti-inflammatory cytokine responses and Th2 responses. These inhibitor effects resulted in reduced granzyme B expression by T cells, chemokine and intracellular cell adhesion molecule 1 (ICAM-1) expression in the brain, and chemokine receptor expression by both myeloid and T cells. These bimodal effects of the MEK1/2 inhibitor treatment on immune responses contributed to decreased parasite biomass, organ inflammation, and immune cell recruitment, preventing tissue damage and death. In summary, we have identified several previously unrecognized immune regulatory processes through which a MEK1/2 inhibitor approach controls malaria parasitemia and mitigates pathogenic effects on host organs.

Study of the cytotoxic/toxic potential of the novel anticancer selenodiazoloquinolone on fibroblast cells and 3D skin model

The new synthetically prepared quinolone derivative 7-ethyl 9-ethyl-6-oxo-6,9-dihydro[1,2,5]selenadiazolo [3,4-h]quinoline-7-carboxylate (E2h) showed in our previous study cytotoxic effects towards tumor cells and immunomodulatory activities on RAW 264.7 cell line murine macrophages. E2h may have a potential use as a novel chemotherapeutic agent with immunomodulatory properties and the ability to induce apoptotic death of cancer cells. The aim of the present study was to examine the antiproliferative/cytotoxic activities of E2h on human non-cancer fibroblast BHNF-1 cells and reconstructed human epidermis EpiDerm™. Further the effects of E2h on tissue structure and morphology were examined. Cytotoxic/toxic studies showed that selenadiazoloquinolone is not toxic on normal human fibroblast cells BHNF-1 and dimensional skin constructs EpiDerm™. Evaluation of morphological changes in EpiDerm™ showed no change in the construction and morphology of skin tissue treated by E2h compared to control.

2-(2-Chlorobenzoyl)-1-(3,4-dimethoxyphenyl)-3-iodoquinolin-4(1H)-one

In the title compound C24H17ClINO4, the iodoquinolinyl moiety (r.m.s. deviation = 0.044 Å) makes dihedral angles of 87.44 (10) and 88.64 (10)° with the chloro- and methoxy-substituted benzene rings, respectively. The methoxy groups are present in synperiplanar and antiperiplanar conformations with respect to the benzene ring they are bound to, as indicated by the C—C—O—C torsion angle values of −16.2 (3) and 177.6 (2)°, respectively. The crystal structure features relatively strong methoxybenzene-C—H...O(quinolinyl) hydrogen bonds, leading to helical supramolecular chains along thea-axis direction. Additional C—H...O interactions along with π-stacking [inter-centroid distance = 3.6070 (16) Å between quinolyl-NC5and C6rings] consolidate the three-dimensional molecular packing.

Transition-metal-free solid phase synthesis of 1,2-disubstituted 4-quinolones via the regiospecific synthesis of enaminones

The transition-metal-free economical solid phase synthesis of 1,2-disubstituted 4-quinolones has been developed via the novel regiospecific synthesis of enaminones.

A novel approach for the synthesis of imidazo and triazolopyridines from dithioesters

Various imidazo- and triazolo-pyridines were synthesised by the intramolecular cyclization of pyridine 2-methylamine and dithioesters under mild conditions.

Tandem approach for the synthesis of 3-sulfenylimidazo[1,5-a]pyridines from dithioesters

Iodine-mediated synthesis of 3-sulfenylimidazo[1,5-a]pyridines via C–H functionalization has been achieved using dithioesters, 2-methylaminopyridines and sulfonyl hydrazides.

Ligand- and catalyst-free intramolecular C-S bond formation: direct access to indalothiochromen- 4-ones

An efficient ligand- and catalyst-free intramolecular S-arylation leading to the direct synthesis of indalothiochromen-4-ones from simple dithioesters under mild conditions has been developed. This method is particularly noteworthy given its experimental simplicity, high generality, and good functional group toleration.

Highly diastereoselective synthesis of polycyclic amines via redox neutral C–H functionalization

Construction of polycyclic amines via C–H functionalization and 3+2 cycloaddition with high diastereoselectivities was achieved under mild conditions.

Synthesis, antimalarial activity, and target binding of dibenzazepine-tethered isoxazolines

A series of dibenzazepine tethered 3,5-disubstituted isoxazolines was synthesized and evaluated for their antimalarial activity usingP. falciparum3D7 strain. Further, the potent molecules were assessed againstP. falciparumD6, W2 and 7G8 strains.