Synthesis of Unsymmetrical Sulfides and Their Oxidation to Sulfones to Discover Potent Antileishmanial Agents

Synthesis of 3-sulfenylindole derivatives from 4-hydroxy-2H-chromene-2-thione and indole using oxidative cross-dehydrogenative coupling reaction and anti-proliferative activity study of some of their sulfone derivatives

The synthesis of hitherto unreported 3-sulfenylindole derivatives is achieved from 4-hydroxy-2H-chromene-2-thione (1) and indole (2) by employing an oxidative cross-dehydrogenative coupling reaction using a combination of 10 mol% of molecular iodine and 1 equivalent of TBHP in DMSO at room temperature. Then, the 3-sulfenylindole derivatives 3a, 3b, 3d, 3f, 3 h, and 3 k were converted into their corresponding sulfone derivatives because of lead likeness properties. Subsequently, a target prediction and docking study of six sulfone derivatives (5a-f) was performed, and four sulfones, namely 5a, 5d, 5e, and 5f, were selected for further in-vitro studies. The four sulfones mentioned above exhibited prominent anti-proliferative activity on breast cancer (MCF7) cell lines. In addition, this reaction was exergonic through quantum chemical analysis of the mechanistic steps. The salient features of this reaction are mild reaction conditions, good yields, and broad substrate scope.

Visible/solar-light-driven thiyl-radical-triggered synthesis of multi-substituted pyridines

A light-triggered synthesis of thio-functionalized pyridines is demonstrated using γ-ketodinitriles, thiols, and eosin Y as the photocatalyst. The reaction proceeds via the selective attack on one of the cyano groups by an in situ generated thiyl radical. The reaction also proceeds with nearly equal efficiency using direct sunlight. Large-scale synthesis and a few useful synthetic transformations of the substituted pyridines are also performed.

Aerobic Oxidative Cascade Thiolation and Cyclization to Construct Indole-Fused Isoquinolin-6(5H)-one Derivatives in EtOH

A practical method to construct sulfenylated indole-fused isoquinolin-6(5H)-one derivatives has been developed. Using eco-friendly ethanol as the solvent and air as the oxidant, this reaction could be compatible with sensitive molecular framework. The utility of the product was well illustrated by further transformations. Moreover, the reaction mechanism was investigated by control experiments.

Nanosized CdS as a Reusable Photocatalyst: The Study of Different Reaction Pathways between Tertiary Amines and Aryl Sulfonyl Chlorides through Visible-Light-Induced N-Dealkylation and C-H Activation Processes

It has been found that the final products of the reaction of sulfonyl chlorides and tertiary amines in the presence of cadmium sulfide nanoparticles under visible light irradiation are highly dependent on the applied reaction conditions. Interestingly, with the change of a reaction condition, different pathways were conducted (visible-light-induced N-dealkylation or sp³ and sp² C-H activation) that lead to different products such as secondary amines and various sulfonyl compounds. Remarkably, all of these reactions were performed under visible light irradiation and an air atmosphere without any additive or oxidant in benign solvents or under solvent-free conditions. During this study, the CdS nanoparticles as affordable, heterogeneous, and recyclable photocatalysts were designed, successfully synthesized, and fully characterized and applied for these protocols. During these studies, intermediates resulting from the oxidation of tertiary amines are trapped during the photoinduced electron transfer (PET) process. The reaction was carried out efficiently with a variety of substrates to give the corresponding products at relatively short times in good to excellent yields in parallel with the use of the visible light irradiation as a renewable energy source. Most of these processes are novel or are superior in terms of cost-effectiveness, safety, and simplicity to published reports.

Transition metal-free and solvent-free calcium carbide promotes the formation of β-keto sulfoxide from acyl chloride and DMSO

A transition metal-free, solvent-free, cheap and readily available calcium carbide promoted one-pot reaction of acid chloride with dimethyl sulfoxide produced β-keto sulfoxide directly.

Reductase of Mutanobactin Synthetase Triggers Sequential C-C Macrocyclization, C-S Bond Formation, and C-C Bond Cleavage

Mutanobactins (MUBs) and their congeners that contain a macrocycle and/or a thiazepane ring are lipopeptides from Streptococcus mutans, a major causative agent of dental caries. Here we show that the C-terminal reductase domain of MubD releases the lipohexapeptide intermediates in an aldehyde form, which enables a spontaneous C-C macrocyclization. In the presence of a thiol group, the macrocyclized MUBs can further undergo spontaneous C-S bond formation and C-C bond cleavage to generate diverse MUB congeners.

Newly synthesized 3-sulfenylindole derivatives from 4-hydroxydithiocoumarin using an oxidative cross dehydrogenative coupling reaction (OCDCR): potential lead molecules for antiproliferative activity

Synthesis of 3-sulfenyl indole derivatives is achieved through oxidative cross-dehydrogenative coupling reaction. A few such newly synthesized compounds have also exhibited anti-proliferative activityviareactive oxygen species mediated cell damage.

An efficient heterogeneous copper fluorapatite (CuFAP)-catalysed oxidative synthesis of diaryl sulfone under mild ligand- and base-free conditions

We report an efficient method for the synthesis of diaryl sulfones using heterogeneous CuFAP-catalysed coupling of sodium salt of aryl sulfonic acid with phenyl boronic acid.

Decanethiol functionalized silver nanoparticles are new powerful leishmanicidals in vitro

We evaluated, for the first time, the leishmanicidal potential of decanethiol functionalized silver nanoparticles (AgNps-SCH) on promastigotes and amastigotes of different strains and species of Leishmania: L. mexicana and L. major isolated from different patients suffering from localized cutaneous leishmaniasis (CL) and L. mexicana isolated from a patient suffering from diffuse cutaneous leishmaniasis (DCL). We recorded the kinetics of promastigote growth by daily parasite counting for 5 days, promastigote mobility, parasite reproduction by CFSE staining's protocol and promastigote killing using the propidium iodide assay. We also recorded IC₅₀'s of promastigotes and amastigotes, therapeutic index, and cytotoxicity by co-culturing macrophages with AgNps-SCH or sodium stibogluconate (Sb) used as reference drug. We used Sb as a reference drug since it is used as the first line treatment for all different types of leishmaniasis. At concentrations 10,000 times lower than those used with Sb, AgNps-SCH had a remarkable leishmanicidal effect in all tested strains of parasites and there was no toxicity to J774A.1 macrophages since > 85% were viable at the concentrations used. Therapeutic index was about 20,000 fold greater than the corresponding one for Sb treated cells. AgNps-SCH inhibited > 80% promastigote proliferation in all tested parasites. These results demonstrate there is a high leishmanicidal potential of AgNps-SCH at concentrations of 0.04 µM. Although more studies are needed, including in vivo testing of AgNps-SCH against different types of leishmaniasis, they can be considered a potential new treatment alternative.

An oxidative cross-coupling reaction of 4-hydroxydithiocoumarin and amines/thiols using a combination of I2 and TBHP: access to lead molecules for biomedical applications

Environmentally benign mild reaction conditions for the construction of new S–N/S–C/S–S bonds under metal free conditions.

One-Pot Synthesis and Evaluation of Antileishmanial Activities of Functionalized S-Alkyl/Aryl Benzothiazole-2-carbothioate Scaffold

The synthesis of hitherto unreported S-alkyl/aryl benzothiazole-2-carbothioate is reported from thiols, oxalyl chloride, and 2-aminothiophenols using 10 mol % n-tetrabutylammonium iodide (TBAI) as catalyst in acetonitrile through multicomponent reaction (MCR) strategy. The present protocol favored formation of benzothiazoles and thioesters via simultaneous formation of C-N and C-S bonds in good yields with a wide range of substrates. A few of the synthesized derivatives were evaluated for their antimicrobial activity against the protozoan parasite Leishmania donovani, a causative agent of visceral leishmaniasis (VL). Further, these compounds displayed no toxicity toward macrophage RAW 264.7 cells and are therefore nontoxic and effective antileishmanial leads. In silico docking studies were performed to understand the possible binding site interaction with trypanothione reductase (TryR).