Synthesis and Structural Characterization of Ferrocenyl-Substituted Aurones, Flavones, and Flavonols

A concise synthesis of thioaurones via NBS-induced cyclization of MOM-protected 2'-mercaptochalcones

A mild and efficient approach for the synthesis of thioaurones via NBS-induced cyclization of methoxymethyl-protected mercapto-chalcones has been developed. This simple method is highly functional group tolerant and provides straightforward access to thioaurones in good to high yields.

Enhancing Antioxidant Effect against Peroxyl Radical-Induced Oxidation of DNA: Linking with Ferrocene Moiety!

As a major member in the family of reactive oxygen species, peroxyl radical is able to abstract hydrogen atom from 4-position of ribose, leading to the collapse of DNA strand. Thus, inhibiting oxidative stress with exogenous antioxidants acts as a promising strategy to protect the integrity of DNA structure and is thereby suggested to be a pathway against developments of related diseases. Ferrocene as an organometallic scaffold is widely applied in the design of organometallic drugs, and redox of Fe(II)/Fe(III) in ferrocene offers advantage for providing electron to radicals. Presented herein are our ongoing studies on ferrocene-appended antioxidants, including McMurry reaction applied to construct ferrocifen; Aldol condensation used to prepare ferrocenyl curcumin; Povarov reaction employed to prepare ferrocenyl quinoline; Biginelli reaction used to construct ferrocenyl dihydropyrimidine; Groebke reaction used to synthesize ferrocenyl imidazo[1,2-a]pyridine; and Passerini three-component reaction as well as Ugi four-component reaction applied to synthesize α-acyloxycarboxamide and bisamide, respectively. It is found that ferrocene moiety is able to enhance antioxidative effect of the aforementioned scaffolds even without the aid of phenolic hydroxyl group. The role of ferrocene in enhancing antioxidative effect can be attributable to trapping radicals, decreasing oxidative potential, and increasing the affinity toward DNA strand. Therefore, ferrocene is worthy to be taken into consideration in the design of drugs in relation to DNA oxidation.

Azide-alkyne cycloaddition en route to 4-aminoquinoline-ferrocenylchalcone conjugates: synthesis and anti-TB evaluation

AIM

Tuberculosis is responsible for 9.6 million infections and 1.5 million deaths in 2015. The development of multidrug-resistant and extensively drug-resistant strains has impeded the development of effective antitubercular therapy. Results/methodology: The present manuscript describes the synthesis of a series of 4-aminoquinoline-ferrocenylchalcone conjugates via Cu-promoted Huisgen's azide-alkyne cycloaddition reaction and evaluation of their antitubercular activities against mc²6230 strain of Mycobacterium tuberculosis. The conjugate 11j proved to be the most potent of the synthesized conjugates with a minimum inhibitory concentration (MIC₉₉) value of 30 μM and proved to be noncytotoxic against HeLa cells.

CONCLUSION

The synthesized conjugates can act as starting point for the development of new antitubercular agents. Synthesis and antitubercular evaluation of 1H-1,2,3-triazole-tethered 4-aminoquinoline-ferrocenylchalcone conjugates. [Formula: see text].

Ferrocene-embedded flavonoids targeting the Achilles heel of multidrug-resistant cancer cells through collateral sensitivity

With the aim to develop anticancer agents acting selectively against resistant tumor cells, we investigated ferrocene embedded into chalcone, aurone and flavone skeletons. These compounds were conceived and then investigated based on the concept of collateral sensitivity, where the target is the Achilles Heel of cancer cells overexpressing the multidrug ABC transporter MRP1. The 14 synthesized compounds were evaluated for their ability to induce efflux of glutathione (GSH) from tumor cells overexpressing MRP1. When tested at 5 and 20 μM, at least one compound from each series was found to be a highly inducer of GSH efflux. The different compounds inducing a high efflux of GSH were evaluated on both sensitive and resistant cell lines, and two of them, belonging to the flavones class were found to be more cytotoxic on resistant cancer cells, with the best selectivity ratio >9.1. Our results bring chemical and biological bases for further optimization.

Combinatorial Synthesis of Structurally Diverse Triazole-Bridged Flavonoid Dimers and Trimers

Flavonoids are a large family of compounds associated with a broad range of biologically useful properties. In recent years, synthetic compounds that contain two flavonoid units linked together have attracted attention in drug discovery and development projects. Numerous flavonoid dimer systems, incorporating a range of monomers attached via different linkers, have been reported to exhibit interesting bioactivities. From a medicinal chemistry perspective, the 1,2,3-triazole ring system has been identified as a particularly attractive linker moiety in dimeric derivatives (owing to several favourable attributes including proven biological relevance and metabolic stability) and triazole-bridged flavonoid dimers possessing anticancer and antimalarial activities have recently been reported. However, there are relatively few examples of libraries of triazole-bridged flavonoid dimers and the diversity of flavonoid subunits present within these is typically limited. Thus, this compound type arguably remains underexplored within drug discovery. Herein, we report a modular strategy for the synthesis of novel and biologically interesting triazole-bridged flavonoid heterodimers and also very rare heterotrimers from readily available starting materials. Application of this strategy has enabled step-efficient and systematic access to a library of structurally diverse compounds of this sort, with a variety of monomer units belonging to six different structural subclasses of flavonoid successfully incorporated.

Green synthesis of aurones and related compounds under solvent-free conditions

3-Coumaranones were condensed with aldehydes on alumina or alumina–potassium fluoride without solvent under microwave irradiation or classical heating. Novel aurones and analogues bearing ferrocenyl, benzodioxole or benzodioxane groups were obtained in good yields without use of heavy metal reagents.

Thiaflavan scavenges radicals and inhibits DNA oxidation: a story from the ferrocene modification

4-Thiaflavan is a sulfur-substituted flavonoid with a benzoxathiin scaffold. The aim of this work is to compare abilities of sulfur and oxygen atom, hydroxyl groups, and ferrocene moiety at different positions of 4-thiaflavan to trap radicals and to inhibit DNA oxidation. It is found that abilities of thiaflavans to trap radicals and to inhibit DNA oxidation are increased in the presence of ferrocene moiety and are further improved by the electron-donating group attaching to thiaflavan skeleton. It can be concluded that the ferrocene moiety plays the major role for thiaflavans to be antioxidants even in the absence of phenolic hydroxyl groups. On the other hand, the antioxidant effectiveness of phenolic hydroxyl groups in thiaflavans can be improved by the electron-donating group. The influences of sulfur and oxygen atoms in thiaflavans on the antioxidant property of para-hydroxyl group exhibit different manners when the thiaflavans are used to trap radicals and to inhibit DNA oxidation.