From β-Amino-γ-sultone to Unusual Bicyclic Pyridine and Pyrazine Heterocyclic Systems: Synthesis and Cytostatic and Antiviral Activities

Oxadiazole: A highly versatile scaffold in drug discovery

As a pharmacologically important heterocycle, oxadiazole paved the way to combat the problem associated with the confluence of many commercially available drugs with different pharmacological profiles. The present review focuses on the potential applications of five-membered heterocyclic oxadiazole derivatives, especially 1,2,4-oxadiazole, 1,2,5-oxadiazole, and 1,3,4-oxadiazole, as therapeutic agents. Designing new hybrid molecules containing the oxadiazole moiety is a better solution for the development of new drug molecules. The designed molecules may accumulate a biological profile better than those of the drugs currently available on the market. The present review will guide the way for researchers in the field of medicinal chemistry to design new biologically active molecules based on the oxadiazole nucleus. Antitubercular, antimalarial, anti-inflammatory, anti-HIV, antibacterial, and anticancer activities of various oxadiazoles have been reviewed extensively here.

Tanshinone IIA: Pharmacology, total synthesis, and progress in structure-modifications

Tanshinone IIA, a major bioactive constituent of Danshen, a Chinese herbal medicine, has gained extensive exploration owing to its unique structural features and multiple promising biological activities. This review focuses on the pharmacology, total synthesis, and structural modifications of tanshinone IIA. We hope this review will contribute to a better understanding of the progress in the field and provide constructive suggestions for further study of tanshinone IIA.

Recent advances on heterocyclic compounds with antiviral properties

In recent years several important viral infections have emerged and antiviral chemotherapeutic agents are not sufficiently effective in clinic, leading to serious human diseases and mortality. Therefore, novel antiviral candidates are urgently desirable, which undoubtedly is essential for the therapy of various fatal and debilitating viral infections. Heterocyclic compounds are obtaining importance in the field of medicinal chemistry because of the broad spectrum of their physiological activities. Among N- and S-containing heterocycles, indole, imidazole, thiazole, pyridine, and quinaxoline derivatives are especially attractive. The present review highlights antiviral behavior of these heterocyclic compounds.

Quinolone-fused cyclic sulfonamide as a novel benign antifilarial agent

Search of potent antifilarial drugs has been a major thrust area in tropical medicine research over the decades. Herein, we report 4,7-dimethyl-3,4,7,8-tetrahydro-3λ⁶-[1,2]thiazino[4,3-f]quinoline-3,3,8-trione (8l) as a new class of antifilarial agent which is extremely potent, with lethality against all the developmental stages (oocyte, microfilaria and adult) of the filarial parasite Setaria cervi. Molecular investigation on its mode of action revealed that 8l is a typical inducer of reactive oxygen species that triggers oxidative stress inside the filarid and further signals induction of apoptosis by activating both intrinsic and extrinsic pathways. Moreover, 8l is also active against Wolbachia, the essential endosymbiont of several human infectious filarids. Selective toxicity against filarial parasites and non-toxic nature in rat model were found as unique traits of 8l to be a future medicine. Taken en masse, this maiden report on a novel quinolone fused cyclic sulfonamide presents a promising therapeutic lead for lymphatic filariasis in future.

4-Amino-2,3-dihydro-1λ6-isothiazole-1,1-dioxides and their chemical properties evaluation

The reactivity of the 4-amino-2,3-dihydro-1H-1λ⁶-isothiazole-1,1-dioxide (β-amino-γ-sultam) framework has not been studied sufficiently. Here we describe the chemical properties of this heterocyclic system toward electrophiles on spiranic and non-spiranic substrates. A variety of C-electrophiles (acetic anhydride, benzoyl chloride, DMFDMA, 4,4-dimethoxybutan-2-one) and heteroatom electrophiles (bromine, nitrosyl acetate) have been explored. Both the C-5 and 4-amino positions of the β-amino-γ-sultam system are able to undergo electrophilic reactions. Heteroatom electrophiles attack the C-5 position, whereas carbo-electrophiles affect the amino group. β-Amino-γ-sultams also were used as starting compounds for the synthesis of 6- or 7-substituted 1λ⁶-isothiazolo[4,5-b]pyridine-1,1-dioxides through condensation reaction and palladium-catalyzed oxidative coupling.

Progress in the synthesis of δ-sultones

Abstract

Sultones, the cyclic esters of hydroxyl sulfonic acids, are a fascinating class of heterocycles and the recent years have witnessed an increasing interest in these molecules, especially in six-ring δ-sultones. The importance of these compounds is either because of their biological properties themselves or due to their versatility as intermediates in more complex target syntheses. Accordingly, the development of new synthesis methods to access δ-sultones is an important and rewarding task which we wish to highlight in this review.

Graphical abstract

New synthesis method for sultone derivatives: synthesis, crystal structure and biological evaluation of S-CA

There has been no remarkable progress in the synthesis of sultones in recent years. To facilitate more detailed studies of this functional group, we found a new method to synthesize the sulfonic acid lactone derivatives and finish its ring-closing reaction. A new sultone derivative, (E)-ethyl 4-oxo-6-styryl-3,4-dihydro-1,2-oxathiine-5-carboxylate 2,2-dioxide (S-CA), was synthesized and structurally identified by ¹H-NMR, ¹³C-NMR, HMQC and X-ray single crystal diffraction analysis. The new rapid synthesis extended the method of ring-closing reaction of sulfonic acid lactone derivatives. The angiogenesis activities of S-CA were evaluated by the chick chorioallantoic membrane (CAM) model. It could selectively suppress small angiogenesis in CAM, without influencing either middle and large angiogenesis. In addition, anticancer efficacy of S-CA was evaluated in vivo using a murine sarcoma S180 model. Reduction of the tumor weight and tumor HE staining regions demonstrated that S-CA (10 mg/kg, intraperitoneal injection) had potent inhibition effects and a 44.71% inhibitory rate in S180 mice. Moreover, an acute toxicity test showed that the LD₅₀ value of S-CA via intraperitoneal injection was 25.624 mg/kg.