Synthesis and Biological Properties of Coumarin Analogue: A Brief Review

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One of the most prominent aromatic organic chemical compound is Coumarin having formula C9H6O2 which is widely known for its benefits in drug industry. Colourless crystalline solid having sweet scent is coumarin’s physical identity. It serves various purposes such as in synthesis of medicines, laser dyes, perfumes and many more. Having enormous usages it becomes important to synthesize such compound so various reactions were performed in order to obtain coumarins. This review explicates the preparation of coumarin by Pechmann Condensation and its biological characteristics.

A review on convenient synthesis of substituted coumarins using reuseable solid acid catalysts

Due to growing concern about chemicals and their impact on the environment, cleaner reaction conditions are needed to be incorporated into chemical synthetic procedures. Recently, the use of heteropolyacid catalysts, mainly reuseable solid acid catalysts, has gained a leading role in organic synthesis due to their environmental and economic considerations and industrial utilization. The high catalytic activity, moisture sensitivity, reusability and inexpensive makes solid supported reagents attractive substituents to conventional Lewis acids. Nowadays synthesis of coumarins and their derivatives has attracted considerable attention from organic and medicinal chemists for many years as a large number of natural products contain this heterocyclic nucleus. In continuation with our investigations into the synthesis of substituted coumarins and due to several advantages of heterogeneous catalysts viz. cost-effective, no side products, high yield of desired products and no toxic waste material, here we report a new approach for the synthesis of substituted coumarins using solid acid catalysts.

BCl3 Catalyzed, Solvent Free Protocol for the Synthesis of Dihydropyrano[ 3,2-b] Chromenediones

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Solvent free synthesis of dihydropyrano[3,2-b]chromenediones was formulated via multicomponent reactions of kojic acid, dimedone and several substituted aromatic aldehydes catalyzed with BCl3. Reactions progressed efficiently and the corresponding heterocyclic products were obtained in good to high yields within short period. The developed protocol is one of the better and efficient alternative methods for the synthesis of dihydropyrano[3,2-b]chromenediones. The simple reaction procedure, easy separation of products, radially available catalyst are certain benefits of this reported protocol.

Syntheses and evaluation of daphnetin derivatives as novel G protein-coupled receptor inhibitors and activators

A series of daphnetin (7,8-dihydroxycoumarin) derivatives 1-22 were synthesized including sixteen new compounds (1-5, 7-14, 18, 21 and 22) and six known compounds (6, 15-17, 19 and 20). Their pharmacological activities on G protein-coupled receptors (GPCRs) were evaluated by double antibody sandwich ELISA (DAS-ELISA) in vitro. Daphnetin derivatives with various substitution patterns/groups were obtained from inhibitors to activators on GPCRs. Derivatives 2-5, 8, 15, 16 and 18-20 possessed moderate activation potency on GPCRs. Among them, derivatives 3-5, 16 and 19 presented significant activation potency on GPCRs with EC₅₀ values in the range of 1.18-1.91 nM. Derivatives 6, 11, 14 and 18 showed significant inhibitory potency on GPCRs with IC₅₀ values in the range of 1.26-1.38 nM. Moreover, the structure-activity relationships (SARs) of daphnetin derivatives were discussed in detail. The new daphnetic-based GPCRs activators and inhibitors have potentials as future drug candidates for the treatment of metabolic diseases.

The role of PMA in enhancing the surface acidity and catalytic activity of a bimetallic Cr-Mg-MOF and its applications for synthesis of coumarin and dihydropyrimidinone derivatives

In the present study, a bimetallic Cr-Mg-MOF was successfully synthesized by the solvothermal method and then modified by loading different amounts of phosphomolybdic acid (PMA) using a simple wet impregnation technique. The morphological and structural properties of the prepared samples were investigated using X-ray diffraction, TEM, SEM, BET and FTIR spectroscopy. Importantly, Mg doping not only caused the Cr-Mg-MOF to have a higher surface area than MIL-101 (Cr) or MOF-74 (Mg), but the strategy of doping metal ions can be an effective way to improve the adsorption performance of MOFs. The surface acidity and the acid strength of the samples were determined using potentiometric titration and the FTIR of pyridine adsorption. The incorporation of PMA crystals gradually enhances both the surface acidity and the acid strength of the PMA/Cr-Mg-MOF catalysts up to 75 wt%. The catalytic performances of the prepared catalysts were tested in two acid-catalyzed organic transformations, namely, 7-hydroxy-4-methyl coumarin and 3,4-dihydropyrimidinone. In the two reactions, the catalytic activity attains the maximum value at 75 wt% PMA loading. The PMA catalysts supported on Cr-Mg-MOF are potentially promising heterogeneous catalysts for acid-catalyzed organic transformations in environmentally friendly processes, to replace the use of conventional homogeneous PMA catalysts.

Sulfamic acid incorporated HKUST-1: a highly active catalyst and efficient adsorbent

Herein we introduce an effective approach for incorporating sulfamic acid (SA) into HKUST-1. The synthesized materials have been characterized using XRD, XPS, BET, FT-IR, SEM, EDX and TEM. The X-ray diffraction pattern of SA@HKUST-1 is analogous to that of parent HKUST-1 in line shape and d-spacing, proving that chemical modification could be obtained without damage to structural solidity. The XPS spectra confirmed successful sulfonation, due to the single S 2p peak being attributable to SO₃H groups at 168 eV. Catalytic efficiency was studied for 7-hydroxy-4-methyl coumarin and 3,4-dihydropyrimidinone synthesis and it was found to be highly dependent on the amount of SA loaded over HKUST-1. Moreover, the adsorptive removal activity of some common organic and inorganic pollutants from water has been studied. To fully understand the adsorption process, the effects of initial dye concentration, pH of solution, adsorbent dosage, contact time and temperature on the adsorption process were successfully studied. Under the optimum conditions 10 wt% SA@HKUST-1 was able to reach the maximum adsorption capacity for Pb²⁺ (298 mg g⁻¹) and Malachite green (290 mg g⁻¹). Hopefully, this will facilitate research on improving the prospective use of MOFs for future applications.

Herein we introduce an effective approach for incorporating sulfamic acid (SA) into HKUST-1.

Coumarins: antifungal effectiveness and future therapeutic scope

The antifungals that are in current clinical practice have a high occurrence of a side effect and multidrug resistance (MDR). Researchers across the globe are trying to develop a suitable antifungal that has minimum side effect as well as no MDR issues. Due to serious undesired effects connected with individual antifungals, it is now necessary to introduce novel and effective drugs having numerous potentials to regulate complex therapeutic targets of several fungal infections simultaneously. Thus, by taking a lead from this subject, synthesis of potent antifungals from coumarin moiety could contribute to the development of promising antifungal. Its resemblance and structural diversity make it possible to produce an auspicious antifungal candidate. Due to the natural origin of coumarin, its presence in diversity, and their broad spectrum of pharmacological activities, it secures an important place for the researcher to investigate and develop it as a promising antifungal in future. This manuscript discusses the bioavailability of coumarin (natural secondary metabolic molecule) that has privileged scaffold for many mycologists to develop it as a broad-spectrum antifungal against several opportunistic mycoses. As a result, several different kinds of coumarin derivatives were synthesized and their antifungal properties were evaluated. This review compiles various coumarin derivatives broadly investigated for antifungal activities to understand its current status and future therapeutic scope in antifungal therapy.

Synthesis of novel benzopyran-connected pyrimidine and pyrazole derivatives via a green method using Cu(ii)-tyrosinase enzyme catalyst as potential larvicidal, antifeedant activities

A series of benzopyran-connected pyrimidine (1a-g) and benzopyran-connected pyrazole (2a-i) derivatives were synthesized via Biginelli reaction using a green chemistry approach. Cu(ii)-tyrosinase was used as a catalyst in the synthesis of compounds 1a-g and 2a-ivia the Biginelli reaction. The as-synthesized compounds were characterized by IR, 1H NMR, 13C NMR, mass spectroscopy, and elemental analysis. The as-synthesized compounds were screened for larvicidal and antifeedant activities. The larvicidal activity was evaluated using the mosquito species Culex quinquefasciatus, and the antifeedant activity was evaluated using the fishes of Oreochromis mossambicus. The compounds 2a-i demonstrated lethal effects, killing 50% of second instar mosquito larvae when their LD50 values were 44.17, 34.96, 45.29, 45.28, 75.96, and 28.99 μg mL-1, respectively. Molecular docking studies were used for analysis based on the binding ability of an odorant binding protein (OBP) of Culex quinquefasciatus with compound 2h (binding energy = -6.12 kcal mol-1) and compound 1g (binding energy = -5.79 kcal mol-1). Therefore, the proposed target compounds were synthesized via a green method using Cu(ii)-enzyme as a catalyst to give high yield (94%). In biological screening, benzopyran-connected pyrazole (2h) was highly active compared with benzopyran-connected pyrimidine (1a-g) series in terms of larivicidal activity.

KHSO4 Catalysed Pechmann Condensation Under Solvent-free Conditions

KHSO4 is used as an alternative to conventional acid catalysts in the Pechmann condensation of phenols with β-ketoesters leading to the formation of substituted coumarins. The method is simple, cost-effective, solvent-free and gives good isolated yields.

Recent developments of C-4 substituted coumarin derivatives as anticancer agents

Cancer is a prominent cause of death in global. Currently, the numbers of drugs that are in clinical practice are having a high prevalence of side effect and multidrug resistance. Researchers have made an attempt to expand a suitable anticancer drug that has no MDR and side effect. Coumarin scaffold became an attractive subject due to their broad spectrum of pharmacological activities. Coumarin derivatives extensively explored for anticancer activities as it possesses minimum side effect along with multi-drug reversal activity. Coumarin derivatives can act by various mechanisms on different tumor cell lines depending on substitution pattern of the core structure of coumarin. Substitution on coumarin nucleus leads to the search for more potent compounds. In this review, we have made an effort to give a synthetic strategy for the preparation of C-4 substituted coumarin derivatives as anticancer agents based on their mechanism of action and also discuss the SAR of the most active compound.

Silica-supported methanesulfonic acid — An efficient solid Brønsted acid catalyst for the Pechmann reaction in the presence of higher n-alkanes

A cost-effective and efficient solid Brønsted acid catalyst was synthesized by loading methanesulfonic acid (MSA) on silica and was used for the acid-catalyzed Pechmann reaction to test the catalytic activity and its reusability. Derivatives of 4-methylcoumarin were synthesized in good yields within short reaction times in the presence of environmentally friendly higher n-alkanes as solvents. The regeneration study of the spent catalyst showed satisfactory results.

Pechmann reaction promoted by boron trifluoride dihydrate

The Pechmann reaction of substituted phenols 1a-e with methyl acetoacetate (2) can be activated by boron trifluoride dihydrate (3) to give the corresponding 4-methylcoumarin derivatives 4a-e in excellent yield (98-99 %).