Visceral leishmaniasis is a fatal parasitic disease, and there is an emergent need for development of effective drugs against this neglected tropical disease. We report here the development of a novel spirooxindole derivative, N-benzyl-2,2=␣-3,3=,5=,6=,7=,7␣,␣=-octahydro2methoxycarbonyl-spiro[indole-3,3=-pyrrolizidine]-2-one (compound 4c), which inhibits Leishmania donovani topoisomerase IB (LdTopIB) and kills the wild type as well as drug-resistant parasite strains. This compound inhibits catalytic activity of LdTopIB in a competitive manner. Unlike camptothecin (CPT), the compound does not stabilize the DNA-topoisomerase IB cleavage complex; rather, it hinders drug-DNA-enzyme covalent complex formation. Fluorescence studies show that the stoichiometry of this compound binding to LdTopIB is 2:1 (mole/mole), with a dissociation constant of 6.65 M. Molecular docking with LdTopIB using the stereoisomers of compound 4c produced two probable hits for the binding site, one in the small subunit and the other in the hinge region of the large subunit of LdTopIB. This spirooxindole is highly cytotoxic to promastigotes of L. donovani and also induces apoptosis-like cell death in the parasite. Treatment with compound 4c causes depolarization of mitochondrial membrane potential, formation of reactive oxygen species inside parasites, and ultimately fragmentation of nuclear DNA. Compound 4c also effectively clears amastigote forms of wild-type and drug-resistant parasites from infected mouse peritoneal macrophages but has less of an effect on host macrophages. Moreover, compound 4c showed strong antileishmanial efficacies in the BALB/c mouse model of leishmaniasis. This compound potentially can be used as a lead for developing excellent antileishmanial agents against emerging drug-resistant strains of the parasite.

We report here DNA metalloenzymes that catalyze the asymmetric Diels-Alder reaction with high conversion, excellent endo/exo selectivities, and enantioselectivities up to-97% ee. Their catalytic-pocket architectures were organized using a rational design strategy based on the Cu(II) ion, the composition of nucleobases, and the incorporation of flexible linkers. Without using the mirror image of B-DNA, DNA metalloenzymes afforded the opposite enantiomer of the Diels-Alder product compared with those obtained using a supramolecular Cu(II)-dmbpy/st-DNA catalyst system. Furthermore, we devised DNA metalloenzymes without the incorporation of an artificial binding ligand and successfully performed a Diels-Alder reaction. This study provides a new perspective on the catalytic repertoire of nucleic acids and will expand the application scope of metalloenzymes.

Polypyrrole stabilised palladium nanoparticles show good catalytic efficiency for the chemoselective transfer hydrogenation of α,β‐unsaturated carbonyl compounds. The catalyst is very specific and selectively hydrogenates the olefins or acetylenes only, without affecting the carbonyl moiety, with an excellent yield of products for a wide range of substrates.

This review deals with the recent applications of the indium trichloride (InCl3) catalyst in the synthesis of a broad spectrum of heterocyclic compounds. Over the years, a number of reviews on the applications of InCl3-catalyzed organic synthesis have appeared in the literature. It is evident that InCl3 has emerged as a valuable catalyst for a wide range of organic transformations due to its stability when exposed to moisture and also in an aqueous medium. The most attractive feature of this review is the application of the InCl3 catalyst for synthesizing bioactive heterocyclic compounds. The study of InCl3-catalyzed organic reactions has high potential and better intriguing aspects, which are anticipated to originate from this field of research.

Near-infrared (NIR) fluorescent probes have been developed as potential bio-materials having profound applications in diagnosis and clinical practice.