Recent advancements in anti-leishmanial research: Synthetic strategies and structural activity relationships

Leishmaniasis is a parasitic neglected tropical disease caused by various species of Leishmania parasite. Despite tremendous advancements in the therapeutic sector and drug development strategies, still the existing anti-leishmanial agents are associated with some clinical issues like drug resistance, toxicity and selectivity. Therefore, several research groups are continuously working towards the development of new therapeutic candidates to overcome these issues. Many potential heterocyclic moieties have been explored for this purpose including triazoles, chalcones, chromone, thiazoles, thiosemicarbazones, indole, quinolines, etc. It is evident from the literature that the majority of anti-leishmanial agents act by interacting with key regulators including PTR-I, DHFR, LdMetAP1, MAPK, 14 α-demethylase and pteridine reductase-I, etc. Also, these tend to induce the production of ROS which causes damage to parasites. In the present compilation, authors have summarized various significant synthetic procedures for anti-leishmanial agents reported in recent years. A brief description of the pharmacological potentials of synthesized compounds along with important aspects related to structural activity relationship has been provided. Important docking outcomes highlighting the possible mode of interaction for the reported compounds have also been included. This review would be helpful to the scientific community to design newer strategies and also to develop novel therapeutic candidates against leishmaniasis.

Chalcones: Retrospective Synthetic Approaches and Mechanistic Aspects of a Privileged Scaffold

This review summarizes the synthetic methodologies used in the last 25 years for the synthesis of chalcones, which are a class of flavonoids having a 1,3-diphenyl-2-propene-1-one backbone. These compounds are considered a hot topic in the field of medicinal chemistry, due to their pharmacological activity and because they are important precursors for the synthesis of heterocyclic compounds with therapeutic applications such as: flavones, flavanones, isoxazolines, benzothiazepines, pyrimidines and pyrazolines derivatives.

MicrowavE Assisted hydrolysis of Meldrum'S Acid Derivatives and decarboxylation of Derived Malonic Acids

Microwave induced hydrolysis of alkyl Medrum's acids and decarboxylation of derived malonic acids using poly-4-vinylpyridine as a catalyst gives high yields of carboxylic acids in a short time.

Solvent-free synthesis, spectral correlations and antimicrobial activities of some aryl E 2-propen-1-ones

Totally 38 aryl E 2-propen-1-ones including nine substituted styryl 4-iodophenyl ketones have been synthesised using solvent-free SiO2-H3PO4 catalyzed Aldol condensation between respective methyl ketones and substituted benzaldehydes under microwave irradiation. The yields of the ketones are more than 80%. The synthesised chalcones were characterized by their analytical, physical and spectroscopic data. The spectral frequencies of synthesised substituted styryl 4-iodophenyl ketones have been correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis. The antimicrobial activities of 4-iodophenyl chalcones have been studied using Bauer-Kirby method.

Hydroxyapatite catalyzed aldol condensation: synthesis, spectral linearity, antimicrobial and insect antifeedant activities of some 2,5-dimethyl-3-furyl chalcones

A series of 2,5-dimethyl-3-furyl chalcones [2E-1-(2,5-dimethyl-3-furyl)-3-(substituted phenyl)-2-propen-1-ones] have been synthesized by Hydrotalcite catalyzed aldol condensation between 3-acetyl-2,5-dimethylfuron and substituted benzaldehydes. Yields of chalcones are more than 80%. These chalcones were characterized by their physical constants and spectral data. The group frequencies of infrared ν(cm(-1)) of CO s-cis and s-trans, CH in-plane and out of plane, CH=CH out of plane, C=C out of plane modes, NMR chemical shifts δ(ppm) of Hα, Hβ, CO, Cα and Cβ of these chalcones were correlated with Hammett substituent constants, F and R parameters using single and multi-regression analyses. From the results of statistical analyses, the effects of substituents on the group frequencies are explained. Antibacterial, antifungal and insect antifeedant activities of these chalcones have been studied.

New eco-friendly animal bone meal catalysts for preparation of chalcones and aza-Michael adducts

Abstract

Two efficient reactions were successfully carried out using Animal Bone Meal (ABM) and potassium fluoride or sodium nitrate doped ABMs as new heterogeneous catalysts under very mild conditions. After preparation and characterization of the catalysts, we first report their use in a simple and convenient synthesis of various chalcones by Claisen–Schmidt condensation and then in an aza-Michael addition involving several synthesized chalcones with aromatic amines. All the reactions were carried out at room temperature in methanol; the chalcone synthesis was also achieved in water environment under microwave irradiation. Doping ABM enhances the rate and yield at each reaction. Catalytic activities are discussed and the ability to re-use the ABM is demonstrated.

Results

For Claisen–Schmidt the use of ABM alone, yields never exceeded 17%. In each entry, KF/ABM and NaNO₃/ABM (79-97%) gave higher yields than using ABM alone under thermic condition. Also the reaction proceeded under microwave irradiation in good yields (72-94% for KF/ABM and 81-97% for NaNO₃/ABM) and high purity. For aza-Michael addition the use of ABM doped with KF or NaNO₃ increased the catalytic activity remarkably. The very high yields could be noted (84-95% for KF/ABM and 81-94% for NaNO₃/ABM).

Conclusion

The present method is an efficient and selective procedure for the synthesis of chalcones an aza-Michael adducts. The ABM and doped ABMs are a new, inexpensive and attractive solid supports which can contribute to the development of catalytic processes and reduced environmental problems.

Fly-ash:H₂SO₄ catalyzed solvent free efficient synthesis of some aryl chalcones under microwave irradiation

Some 2E aryl chalcones have been synthesized using greener catalyst Fly-ash:H(2)SO(4) assisted solvent free environmentally benign Crossed-Aldol reaction. The yields of chalcones are more than 90%. The synthesized chalcones are characterized by their physical constants and spectral data.

Fast and robust route to hydroporphyrin-chalcones with extended red or near-infrared absorption

The reaction of an acetylchlorin or diacetylbacteriochlorin with an aldehyde under microwave conditions readily affords the corresponding hydroporphyrin-chalcone. The aldehydes include aryl aldehydes, cinnamaldehyde, and all-trans-retinal. The chalcone causes a bathochromic shift of the long-wavelength absorption band of the hydroporphyrin by up to 24 nm. The facile conjugation and wavelength tunability should make such constructs valuable for fundamental spectroscopic studies as well as diverse photochemical applications in the relatively unexplored red and near-infrared spectral regions.