Cancer is a type of human cell degenerative disease that has afflicted a large number of people for years. Cancer is caused due to the abnormal proliferation of cells in any part of the body. Most of the prescribed anticancer drugs are synthetic in nature and have been reported with enormous adverse effects. The researchers are very much enthusiastic about the use of natural compounds and their derivatives, which have been reported with less toxicity. Natural compounds have emerged as promising synergistic compounds with potential anticancer effects. In vitro anticancer activity of natural compounds with special reference to camphor and menthol has been investigated against different cancer cell lines. It has been found that camphor and menthol derivatives have potential cytotoxic activity. The present literature review outlines the various methods for the synthesis of camphor and menthol derivatives, which have potential cytotoxic activity. It highlights various cancer cell lines, which are the target of these camphor and menthol derivatives as ligands, along with structure-activity studies.

Benzothiazole is a bicyclic heterocyclic compound that contains benzene fused with 1, 3- thiazole ring. Several researches established the potential of benzothiazoles as important moiety in various adverse pharmacological conditions. Benzothiazole and its derivatives have been in use and marketed as anti-microbial, anti-inflammatory, anti-diabetic, anti-oxidant, anti-convulsant, antitumor, etc. The variations in pharmacological potentials of benzothiazole and its derivatives have been rational with their chemical structure. Nowadays, hybridization of two or more pharmacophores to synthesize a single molecule with potent pharmacological action is used. This helps to synergize pharmacological properties, make interaction possible with many targets, or minimize the adverse effects associated with them. Several synthetic approaches have been reported for benzothiazole and its derivatives. In this present review, we focused on recently adopted synthetic approaches for the synthesis of the benzothiazole nucleus and its derivatives. The structure-activity relationship in relation to different pharmacological activities has also been highlighted to provide a good understanding to the researchers for future research on benzothiazoles.

Heterocyclic compounds constitute the most important part of medicinal as well as organic chemistry. Most of the marketed drugs possess therapeutic activity because of the presence of heterocyclic scaffolds as part of their structure. A slight change in the structure of the heterocyclic moieties may result in a major change in the therapeutic response of the drug candidate. Among all heterocycle compounds, the compounds containing nitrogen and sulfur atoms serve as a unique resource for drug development, such as benzothiazoles. Benzothiazole is a benzofused heterocyclic that is widely reported as a constituent of naturally occurring chemicals and chiefly responsible for their pharmacological potential. It was also reported that the pharmacological activity of BTA may also be influenced by its coupling with aldehydes, ketones, or hydrazines to form respected benzothiazole-hydrazone derivatives. The present comprehensive review consists of various synthesis methods, biological activities, and structure-activity relationships of and targets of benzothiazole and benzothiazole-hydrazone derivatives to provide a wide range of information to medicinal chemists for future research work.

It has been established on the basis of reported research that benzimidazoles and their analogs are active scaffolds. Benzimidazole is a benzofused imidazole compound that is present in several marketed molecules with a wide range of uses that established its importance in pharmaceutical sectors and industry. Drugs with a benzimidazole nucleus have unique structural characteristics and an electron-rich environment that allows them to attach to a variety of physiologically significant sites and produce a variety of actions. The development of benzimidazole heterocyclic molecules as antihistaminic (H1-receptor antagonist, for example, bilastine; 5-HT3 antagonist, for example, leri-setron); antimicrobial (antibiotic, for example, ridinilazole); antiulcer (proton pump inhibitor (PPI), for example, ilaprazole); antihypertensive (calcium channel blocker, for example, mibefradil); and drugs used to treat cancer include those that are antiparasitic (specifically anthelmintic, such as fubendazole), antipsychotic (D2 receptor antagonist, such as clopimozide), analgesic (opioid analgesic, such as clonitazene), and phosphodiesterase inhibitor (PDE3 inhibitor, such as adibendan). Due to its broad applications, scientists are continuously enthralled by benzimidazoles and their derivatives to study their chemistry. Several synthesis strategies can prepare benzimidazole or its derivatives and the focus will always be on new, greener, and more economical ways for its synthesis. Among all methods, catalytic cyclization, catalytic coupling, and catalytic reactions are the most used approaches for the synthesis of benzimidazoles and their analogs. The present review entitled various synthetic approaches for synthesizing benzimidazole from 2009 to 2021 and its derivatives, which will be very useful to researchers for developing benzimidazole moieties.

Epilepsy is a chronic neurological disorder characterized by periodic and unpredictable seizures affecting the neurobiological, psychological, cognitive, economic, and social well-being of patients. It is one of the causes of concern in developed as well as developing countries as currently marketed drugs are not capable of providing protection against it. Although several heterocyclic moieties have been frequently used as building blocks for the preparation of anticonvulsant drugs, more focused and consistent research on the synthesis of potential molecules with less adverse effects is the need of the hour. It can be concluded on the basis of available research reports that among several heterocyclic compounds, benzo-fused five-membered heterocyclic moieties (benzothiazole and benzimidazole) have been utilized far less than their great potential as building blocks for the synthesis of anticonvulsant drugs. Various reports clearly established that the required pharmacophore model could be easily achieved through benzothiazole and benzimidazole moieties as two hetero atoms and aryl rings are present in the structure. The present study highlights various synthetic approaches for anticonvulsant benzothiazole and benzimidazole derivatives with their structure-activity relationship studies in order to provide a trove of knowledge to medicinal chemists for future research.

Heterocyclic compounds are fundamental building blocks for developing novel bioactive compounds. Due to their extensive uses in both industrial and synthetic organic chemistry, quinoline and benzimidazole have recently become important heterocycles. Clinical trials have investigated quinoline and benzimidazole analogues to treat a variety of illnesses, including cancer, bacterial and fungal infection, DNA damage, etc. Medicinal chemists are paying attention to nitrogen-containing hybrid heterocyclic compounds that have a wide range of therapeutical potential with lesser adverse effects. Many efforts have been made to find new and more efficient ways to synthesize these molecules. However, microbial resistance is becoming a major threat to the scientific community; hence, the necessity for the discovery and development of novel antimicrobial drugs with novel modes of action is becoming highly significant. One strategy to overcome this problem is to produce hybrid molecules by combining two or more bioactive heterocyclic moieties in a single molecular platform. Based on established research data on quinoline- bearing benzimidazole derivatives, it can be concluded that both moieties are used for the synthesis of promising therapeutically active agents. This present review comprises the synthetic approaches of biologically active quinolines containing benzimidazole derivatives with their structure-activity relationship studies to provide an overview of the work done on quinoline derivatives to the medicinal chemist for future research.