Insights into the structural patterns of the antileishmanial activity of bi- and tricyclic N-heterocycles

[3+3]-Annulation of Cyclic Nitronates with Vinyl Diazoacetates: Diastereoselective Synthesis of Partially Saturated [1,2]Oxazino[2,3-b][1,2]oxazines and Their Base-Promoted Ring Contraction to Pyrrolo[1,2-b][1,2]oxazine Derivatives

A rhodium(II)-catalyzed reaction of cyclic nitronates (5,6-dihydro-4H-1,2-oxazine N-oxides) with vinyl diazoacetates proceeds as a [3+3]-annulation producing bicyclic unsaturated nitroso acetals (4a,5,6,7-tetrahydro-2H-[1,2]oxazino[2,3-b][1,2]oxazines). Optimization of reaction conditions revealed the use of Rh(II) octanoate as the preferred catalyst in THF at room temperature, which allows the preparation of target products in good yields and excellent diastereoselectivity. Under basic conditions, namely, the combined action of DBU and alcohol, these nitroso acetals undergo ring contraction of an unsaturated oxazine ring into the corresponding pyrrole. Both transformations can be performed in a one-pot fashion, thus constituting a quick approach to oxazine-annulated pyrroles from available starting materials, such as nitroalkenes, olefins, and diazo compounds.

Novel phenanthridine amide analogs as potential anti-leishmanial agents: In vitro and in silico insights

In the current work, sixteen novel amide derivatives of phenanthridine were designed and synthesized using 9-fluorenone, 4-Methoxy benzyl amine, and alkyl/aryl acids. The characterization of the title compounds was performed using LCMS, elemental analysis, ¹HNMR, ¹³CNMR and single crystal XRD pattern was also developed for compounds A8. All the final analogs were screened in vitro for anti-leishmanial activity against promastigote form of L. infantum strain. Among the tested analogs, four compounds (A-06, A-11, A-12, and A-15) exhibited significant anti-leishmanial activity with EC₅₀ value ranges from 8.9 to 21.96 μM against amastigote forms of tested L. infantum strain with SI ranges of 1.0 to 4.3. From the activity results it was found that A-11 was the most active compound in both promastigote and amastigotes forms with EC₅₀ values 8.53 and 8.90 µM respectively. In-silico ADME prediction studies depicted that the titled compounds obeyed Lipinski's rule of five as that of the approved marketed drugs. The predicted in-silico toxicity profile also confirmed that the tested compounds were non-toxic. Finally, molecular docking and molecular dynamics study was also performed for significantly active compound (A-11) in order to study it's putative binding pattern at the active site of the selected leishmanial trypanothione reductase target as well as to understand the stability pattern of target-ligand complex for 100 ns. Single crystal XRD of compound A-08 revealed that the compound crystallizes in monoclinic C2/c space group and showed interesting packing arrangements.

A Computational Approach to Explore the Interaction of Semisynthetic Nitrogenous Heterocyclic Compounds with the SARS-CoV-2 Main Protease

In the context of the ongoing coronavirus disease 2019 (COVID-19) pandemic, numerous attempts have been made to discover new potential antiviral molecules against its causative agent, SARS-CoV-2, many of which focus on its main protease (M^pro). We hereby used two approaches based on molecular docking simulation to explore the interaction of four libraries of semisynthetic nitrogenous heterocyclic compounds with M^pro. Libraries L1 and L2 contain 52 synthetic derivatives of the natural compound 2-propylquinoline, whereas libraries L3 and L4 contain 65 compounds synthesized using the natural compound physostigmine as a precursor. Validation through redocking suggested that the rigid receptor and flexible receptor approaches used for docking were suitable to model the interaction of this type of compounds with the target protein, although the flexible approach seemed to provide a more realistic representation of interactions within the active site. Using empirical energy score thresholds, we selected 58 compounds from the four libraries with the most favorable energy estimates. Globally, favorable estimates were obtained for molecules with two or more substituents, putatively accommodating in three or more subsites within the M^pro active site. Our results pave the way for further experimental evaluation of the selected compounds as potential antiviral agents against SARS-CoV-2.

Antileishmanial activity of a new chloroquine analog in an animal model of Leishmania panamensis infection

Leishmania panamensis is a relevant causative agent of tegumentary leishmaniasis in several Latin American countries. Available antileishmanial drugs have several limitations including relatively high toxicity, difficult administration, high production costs and the emergence of resistance in circulating strains. Therefore, the identification of new molecules as potential therapeutics for leishmaniasis is of great relevance. Here, we developed a murine model of L. panamensis infection and evaluated the effect of a new compound in vivo. After treatment of animals with the compound, we observed a significant reduction of inflammation and parasite load at the inoculation site, in a dose-dependent manner. We observed a reduction in IL-10 production by popliteal lymph nodes cells of infected mice. These results pave the way for future evaluation of this compound as a potential antileishmanial drug or as a suitable scaffold for lead optimization strategies.

Recent Advances in the Chemistry of Conjugated Nitrosoalkenes and Azoalkenes

This review aims to present the most recent contributions in the chemistry of nitrosoalkenes and azoalkenes, highlighting the chemical behavior that makes them important and versatile building blocks in organic synthesis. These are heterodienes used in the assembly of a variety of heterocyclic systems, spanning from five- to seven-membered heterocycles, as well as for the functionalization of heterocycles.

Modular Three-Component Synthesis of 4-Aminoquinolines via an Imidoylative Sonogashira/Cyclization Cascade

We developed a one-pot, two-stage synthetic route to substituted 4-aminoquinolines involving an imidoylative Sonogashira coupling followed by acid-mediated cyclization. This three-component reaction affords pharmaceutically valuable 4-aminoquinolines in a one-pot procedure from readily available starting materials. The reaction tolerates various substituents on the arene as well as the use of secondary and even primary isocyanides. Additionally, the wide tolerance for functionalized isocyanides allows for the one-pot synthesis of various substituted chloroquine analogues as well as other medicinally relevant products.

T. Vo A, Tristan A, Carreño L, Quijada M, Nguyen VT, Perry G, Larionov OV, Lleonart R, Fernández PL. Identification of Inhibitors of CD36-Amyloid Beta Binding as Potential Agents for Alzheimer's Disease

Neuroinflammation is one of the hallmarks of Alzheimer's disease pathology. Amyloid β has a central role in microglia activation and the subsequent secretion of inflammatory mediators that are associated with neuronal toxicity. The recognition of amyloid β by microglia depends on the expression of several receptors implicated in the clearance of amyloid and in cell activation. CD36 receptor expressed on microglia interacts with fibrils of amyloid inducing the release of proinflammatory cytokines and amyloid internalization. The interruption of the interaction CD36-amyloid β compromises the activation of microglia cells. We have developed and validated a new colorimetric assay to identify potential inhibitors of the binding of amyloid β to CD36. We have found seven molecules, structural analogues of the Trichodermamide family of natural products that interfere with the interaction CD36-amyloid β. By combining molecular docking and dynamics simulations, we suggested the second fatty acids binding site within the large luminal hydrophobic tunnel, present in the extracellular domain of CD36, as the binding pocket of these compounds. Free energy calculations predicted the nonpolar component as the driving force for the binding of these inhibitors. These molecules also inhibited the production of TNF-α, IL-6, and IL-1β by peritoneal macrophages stimulated with fibrils of amyloid β. This work serves as a platform for the identification of new potential anti-inflammatory agents for the treatment of Alzheimer's disease.