Chemistry strategies in early drug discovery: an overview of recent trends

Recent Advances in the Development of Greener Methodologies for the Synthesis of Benzothiazoles

The benzothiazole ring system has been recognised with crucial pharmacophoric features being present among various approved drugs and clinical and pre-clinical candidates. The medicinal importance of this privileged scaffold stimulated the interest of synthetic medicinal/ organic chemists for the synthesis of its derivatives due to their diverse biological applications. In most of the reports in the literature, benzothiazoles were synthesized by cyclocondensation of 2- aminothiophenol with either carboxylic acid and its derivatives or aldehydes. However, many of these procedures involve reaction conditions that are not in conformity with sustainable chemistry development. The negative impact of chemicals and their manufacturing processes on the environment, human health, and biodiversity raises safety concerns. On the other hand, the utilization of non-renewable energy sources, use of rare earth metals as catalysts, involvement of costly chemicals, prolonged reaction time at high temperatures, and considerable waste generation diminish the greener impact of these reaction methodologies and make them non-sustainable. In order to avoid such drawbacks of the non-sustainable practices in the synthesis of benzothiazoles, there have been continuous efforts to develop greener methodologies for the construction of this bioactive scaffold. This review aims to delve into the literature reports on the recent advancements in the development of greener methodologies for the synthesis of bioactive benzothiazoles.

Click Reaction Inspired Enzyme Inhibitors in Diabetes Care: An Update in the Field of Chronic Metabolic Disorder

Diabetes is a chronic metabolic disorder that impacts all age groups and affects a large population worldwide. Humans receive glucose from almost every food source, and after absorption from the gut, it reaches the liver, which functions as the distribution center for it. The insulin-responsive glucose transporter type 4 (GLUT-4) is a major carrier of glucose to the various cells (majorly expressed in myocytes, adipocytes, and cardiomyocytes) in a well-fed state. In fasting periods, the glucose supply is maintained by glycogenolysis and gluconeogenesis. In diabetes, the distribution of glucose is hampered due to several reasons. Furthermore, to treat this disorder, several drugs have been synthesized, and click chemistry plays an important role. A more recent concept for producing pharmaceuticals with a click chemistry approach makes any reaction more practical and stereospecific, along with a higher yield of products and a smaller number of by-products. This approach comprises a compiled study of the activity of numerous compelling antidiabetic drugs containing 1,2,3-triazole derivatives supported by click chemistry. In this review, we discuss the synthetic antidiabetic drugs made via click chemistry and their commendable role in improving diabetes care.

Insights into the Biological Activities and Substituent Effects of Pyrrole Derivatives: The Chemistry-Biology Connection

Pyrrole, with its versatile heterocyclic ring structure, serves as a valuable template for generating a diverse range of lead compounds with various pharmacophores. Researchers and scientists globally are intrigued by pyrrole and its analogs for their broad pharmacological potential, prompting thorough investigations aimed at advancing human welfare. This comprehensive review delves into the diverse activities exhibited by pyrrole compounds, encompassing their synthesis, reactions, and pharmacological properties alongside their derivatives. In addition to detailing the characteristics of pyrrole and its derivatives within the context of green chemistry, the review also examines microwave-assisted reactions. It provides insights into their chemical structures, natural occurrences, and potential applications across various domains. Furthermore, the article investigates structural alterations of pyrrole compounds and their implications on their functionality, highlighting their versatility as foundational elements for both functional materials and bioactive compounds. The review emphasizes the need for ongoing research and development in the field of pyrrole compounds to discover new activities and benefits.

Chemical synthetic approaches to mimic the TRAIL: promising cancer therapeutics

Apoptosis is programmed cell death that eliminates undesired cells to maintain homeostasis in metazoan. Aberration of this process may lead to cancer genesis. The tumor necrosis factor related apoptosis inducing ligand (TRAIL) induces apoptosis in cancer cells after ligation with death receptors (DR4/DR5) while sparing most normal cells. Therefore, strategies to induce apoptosis in cancer cells by mimicking the TRAIL emerge as a promising therapeutic tool. Hence, approaches are taken to develop TRAIL/DR-based cancer therapeutics. The recombinant soluble TRAIL (rhTRAIL) and death receptor agonistic antibodies were produced and tested pre-clinically and clinically. Pre-clinical and clinical trial data demonstrate that these therapeutics are safe and relatively well tolerated. But some of these therapeutics failed to exert adequate efficacy in clinical settings. Besides these biotechnologically derived therapeutics, a few chemically synthesized therapeutics are reported. Some of these therapeutics exert considerable efficacy in vitro and in vivo. In this review, we will discuss chemically synthesized TRAIL/DR-based therapeutics, their chemical and biological behaviour, design concepts and strategies that may contribute to further improvement of TRAIL/DR-based therapeutics.

Amoebicidal effect of synthetic indoles against Acanthamoeba spp.: a study of cell death

Organic and synthetic chemistry plays a crucial role in drug discovery fields. Moreover, chemical modifications of available molecules to enhance their efficacy, selectivity and safety have been considered as an attractive approach for the development of new bioactive agents. Indoles, a versatile group of natural heterocyclic compounds, have been widely used in pharmaceutical industry due to their broad spectrum of activities including antimicrobial, antitumoral and anti-inflammatory among others. Herein, we report the amoebicidal activity of different indole analogs on Acanthamoeba castellanii Neff. Among the 40 tested derivatives, eight molecules were able to inhibit this protistan parasite. The structure-activity relationship (SAR) analysis of their anti-Acanthamoeba activity would suggest that a carboxylation of C-3 position and the incorporation of halogen as chlorine/fluorine would enhance their biological profile, presumably by increasing their lipophilicity and therefore their ability to cross the cell membrane. Fluorescence image base system was used to investigate the effect of indole 6o c-6 on the cytoskeleton network and various programmed cell death features. We were able to highlight that the methyl 6-chloro-1H-indole-3-carboxylate could induce program cell death by the mitochondrial dysfunction.

Recent advances in catalytic and non-catalytic epoxidation of terpenes: a pathway to bio-based polymers from waste biomass

Epoxides derived from waste biomass are a promising avenue for the production of bio-based polymers, including polyamides, polyesters, polyurethanes, and polycarbonates. This review article explores recent efforts to develop both catalytic and non-catalytic processes for the epoxidation of terpene, employing a variety of oxidizing agents and techniques for process intensification. Experimental investigations into the epoxidation of limonene have shown that these methods can be extended to other terpenes. To optimize the epoxidation of bio-based terpene, there is a need to develop continuous processes that address limitations in mass and heat transfer. This review discusses flow chemistry and innovative reactor designs as part of a multi-scale approach aimed at industrial transformation. These methods facilitate continuous processing, improve mixing, and either eliminate or reduce the need for solvents by enhancing heat transfer capabilities. Overall, the objective of this review is to contribute to the development of commercially viable processes for producing bio-based epoxides from waste biomass.

Microwave-Accelerated McKenna Synthesis of Phosphonic Acids: An Investigation

Phosphonic acids represent one of the most important categories of organophosphorus compounds, with myriad examples found in chemical biology, medicine, materials, and other domains. Phosphonic acids are rapidly and conveniently prepared from their simple dialkyl esters by silyldealkylation with bromotrimethylsilane (BTMS), followed by desilylation upon contact with water or methanol. Introduced originally by McKenna, the BTMS route to phosphonic acids has long been a favored method due to its convenience, high yields, very mild conditions, and chemoselectivity. We systematically investigated microwave irradiation as a means to accelerate the BTMS silyldealkylations (MW-BTMS) of a series of dialkyl methylphosphonates with respect to solvent polarity (ACN, dioxane, neat BTMS, DMF, and sulfolane), alkyl group (Me, Et, and iPr), electron-withdrawing P-substitution, and phosphonate-carboxylate triester chemoselectivity. Control reactions were performed using conventional heating. We also applied MW-BTMS to the preparation of three acyclic nucleoside phosphonates (ANPs, an important class of antiviral and anticancer drugs), which were reported to undergo partial nucleoside degradation under MW hydrolysis with HCl at 130-140 °C (MW-HCl, a proposed alternative to BTMS). In all cases, MW-BTMS dramatically accelerated quantitative silyldealkylation compared to BTMS with conventional heating and was highly chemoselective, confirming it to be an important enhancement of the conventional BTMS method with significant advantages over the MW-HCl method.

Metal catalyzed C-H functionalization on triazole rings

The present review covers advancement in the area of C-H functionalization on triazole rings, by utilizing various substrates with palladium or copper as catalysts, and resulting in the development of various substituted 1,2,3- and 1,2,4-triazoles. Synthesis of these substituted compounds is necessary from the perspective of pharmaceutical, medicinal, and materials chemistry.

Dual Roles of Azide: Dearomative Dimerization of Furfuryl Azides

A dearomative dimerization of furfuryl azides for the construction of furfuryl triazoles is developed. As a rare leaving group, azide is capable of initiating the generation of a furfuryl cation under the Lewis acid-catalyzed conditions, followed by reacting with the other azide to realize an intermolecular [3 + 2] cycloaddition/furan ring-opening cascade. By extending the reaction time, a fragmentation reaction of resulting furfuryl triazoles occurs to afford 1H-triazoles in high yield. Control studies demonstrated that key furfuryl cations also can be obtained from furfuryl triazoles. Furthermore, a chemoselective cross-cycloaddition can be achieved between furfuryl azides and a benzyl azide.

Synthesis and development of seven-membered constrained cyclic urea based PSMA inhibitors via RCM

Intramolecular ring-closing metathesis on an N,N-diallyl Glu-urea-Gly substrate affords 7-membered cyclic ureas as inhibitors of prostrate specific membrane antigen (PMSA).

Acid-catalyzed three-component addition of carbonyl compounds with 1,2,3-triazoles and indoles

A facile and efficient acid-catalyzed three-component reaction of indoles, 1-tosyl-1,2,3-triazoles and carbonyl compounds has been developed. The use of TsOH with a small amount of water significantly promoted the reaction yield. This method provided a general and one-pot approach for the synthesis of structurally diverse C3-alkylated indole derivatives. The alkylation exclusively occurred at the N² position of triazoles. Various functional groups were tolerated under the optimized simple reaction conditions.

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

Desulfonylative alkylation of N-tosyl-1,2,3-triazoles under metal-free conditions leading to β-triazolylenones is reported here. The present study encompasses the synthesis of triazoles with a new substitution pattern in a single step from cyclic 1,3-dicarbonyl compounds and N-tosyl triazole in moderate to high yields. Our synthesis takes place with complete regioselectivity as confirmed by crystallographic analysis which is rationalized by a suitable mechanistic proposal. This method provides an efficient, versatile and straightforward strategy towards the synthesis of new functionalized 1,2,3-triazoles.

Microfluidic Modules Integrated with Microwave Components-Overview of Applications from the Perspective of Different Manufacturing Technologies

The constant increase in the number of microfluidic-microwave devices can be explained by various advantages, such as relatively easy integration of various microwave circuits in the device, which contains microfluidic components. To achieve the aforementioned solutions, four trends of manufacturing appear—manufacturing based on epoxy-glass laminates, polymer materials (mostly common in use are polydimethylsiloxane (PDMS) and polymethyl 2-methylpropenoate (PMMA)), glass/silicon substrates, and Low-Temperature Cofired Ceramics (LTCCs). Additionally, the domains of applications the microwave-microfluidic devices can be divided into three main fields—dielectric heating, microwave-based detection in microfluidic devices, and the reactors for microwave-enhanced chemistry. Such an approach allows heating or delivering the microwave power to the liquid in the microchannels, as well as the detection of its dielectric parameters. This article consists of a literature review of exemplary solutions that are based on the above-mentioned technologies with the possibilities, comparison, and exemplary applications based on each aforementioned technology.

Cinnamide derived pyrimidine-benzimidazole hybrids as tubulin inhibitors: Synthesis, in silico and cell growth inhibition studies

An approach in modern medicinal chemistry to discover novel bioactive compounds is by mimicking diverse complementary pharmacophores. In extension of this strategy, a new class of piperazine-linked cinnamide derivatives of benzimidazole-pyrimidine hybrids have been designed and synthesized. Their in vitro cytotoxicity profiles were explored on selected human cancer cell lines. Specifically, structural comparison of target hybrids with tubulin-DAMA-colchicine and tubulin-nocodazole complexes has exposed a deep position of benzimidazole ring into the αT5 loop. All the synthesized compounds were demonstrated modest to interesting cytotoxicity against different cancer cell lines. The utmost cytotoxicity has shown with an amine linker of benzimidazole-pyrimidine series, with specificity toward A549 (lung cancer) cell line. The most potent compound in this series was 18i, which inhibited cancer cell growth at micromolar concentrations ranging 2.21-7.29 µM. Flow cytometry studies disclosed that 18i inhibited the cells in G2/M phase of cell cycle. The potent antitumor activity of 18i resulted from enhanced microtubule disruption at a similar level as nocodazole on β-tubulin antibody, explored using immunofluorescence staining. The most active compound 18i also inhibited tubulin polymerization with an IC₅₀ of 5.72 ± 0.51 µM. In vitro biological analysis of 18i presented apoptosis induction on A549 cells with triggering of ROS generation and loss of mitochondrial membrane potential, resulting in DNA injury. In addition, 18i displayed impairment in cellular migration and inhibited the colony formation. Notably, the safety profile of most potent compound 18i was revealed by screening against normal human pulmonary epithelial cells (L132: IC₅₀: 69.25 ± 5.95 μM). The detailed binding interactions of 18i with tubulin was investigated by employing molecular docking, superimposition and free energy analyses. Thus remarks made in this study established that pyrimidine-benzimidazole hybrids as a new class of tubulin polymerization inhibitors with significant anticancer activity.

An Overview on Steroids and Microwave Energy in Multi-Component Reactions towards the Synthesis of Novel Hybrid Molecules

In recent years, hybrid systems are gaining considerable attention owing to their various biological applications in drug development. Generally, hybrid molecules are constructed from different molecular entities to generate a new functional molecule with improved biological activities. There already exist a large number of naturally occurring hybrid molecules based on both non-steroid and steroid frameworks synthesized by nature through mixed biosynthetic pathways such as, a) integration of the different biosynthetic pathways or b) Carbon- Carbon bond formation between different components derived through different biosynthetic pathways. Multicomponent reactions are a great way to generate efficient libraries of hybrid compounds with high diversity. Throughout the scientific history, the most common factors developing technologies are less energy consumption and avoiding the use of hazardous reagents. In this case, microwave energy plays a vital role in chemical transformations since it involves two very essential criteria of synthesis, minimizing energy consumption required for heating and time required for the reaction. This review summarizes the use of microwave energy in the synthesis of steroidal and non-steroidal hybrid molecules and the use of multicomponent reactions.

Empowering the Medicinal Applications of Bisphosphonates by Unveiling their Synthesis Details

Bisphosphonates (BPs), well-known medicinal compounds used for osteoporosis management, are currently the target of intensive research, from basic pre-formulation studies to more advanced stages of clinical practice. The high demand by the pharmaceutical industry inherently requires an easy, efficient and quick preparation of BPs. Current synthetic procedures are, however, still far from ideal. This work presents a comprehensive compilation of reports on the synthesis of the commercially available bisphosphonates that are pharmaceutical active ingredients. Current limitations to the conventional synthesis are assessed, and paths towards their improvement are described, either through the use of alternative solvents and/or by selecting appropriate ratios of the reactants. Innovative processes, such as microwave-assisted synthesis, are presented as more environmental-friendly and effective methods. The main advantages and setbacks of all syntheses are provided as a way to clarify and promote the development of simpler and improved procedures. Only in this way one will be able to efficiently respond to the future high demand of BPs, mostly due to the increase in life span in occidental countries.

Stereoselective Four-Component Synthesis of Functionalized 2,3-Dihydro-4-Nitropyrroles

We report a metal-free and stereoselective four-component reaction between α-ketoamides, amines, aromatic aldehydes and β-nitroalkenes or β-pivaloxy-nitroalkanes to obtain 2,3-dihydro-4-nitropyrroles functionalized in every position. The heterocycles accessible using this reaction may have utility in the synthesis of pharmacologically active compounds.

1,3,4-Oxadiazoles by Ugi-Tetrazole and Huisgen Reaction

Easy to perform, functional group tolerant, and short syntheses of the privileged scaffold oxadiazole are highly desired. Here, a metal-free protocol for MCR-based synthesis of 2,5-disubstituted 1,3,4-oxadiazoles via a Ugi-tetrazole/Huisgen sequence was developed. Optimization and scope and limitations of this short and general sequence are described. The reaction was also successfully performed on a gram scale.

Microwave-accelerated diastereoselective catalyst-free one-pot four-component synthesis of 2-(N-carbamoylacetamide)-substituted 2,3-dihydrothiophenes in glycerol

In the current study, glycerol was successfully employed as a nonvolatile, non-toxic, non-flammable, biodegradable, very cheap, easily accessible, and efficient reaction medium for the microwave-enhanced diastereoselective synthesis of 2-(N-carbamoylacetamide)-substituted 2,3-dihydrothiophenes via a catalyst-free one-pot four-component reaction. A versatile range of starting materials were used, and diverse products were obtained in good to excellent yields and very short reaction times. Moreover, the reaction medium was recovered and reused several times without any loss of the efficiency.

Synthesis of multisubstituted arylsulfones via a one-pot, three-component [3 + 3] benzannulation reaction

A one-pot, three-component [3 + 3] benzannulation reaction of α,β-unsaturated carbonyl compounds, bromoallylic sulfones, and sodium sulfinates provided multisubstituted arylsulfones with moderate to good yields.

Ruthenium polypyridyl complex-catalysed aryl alkoxylation of styrenes: improving reactivity using a continuous flow photo-microreactor

Previously, we reported the ruthenium polypyridyl complex-catalysed aryl alkoxylation reaction of styrenes with aryldiazonium salts.

Caught in-between: System for in-flow inactivation of enzymes as an intermediary step in "plug-and-play" microfluidic platforms

The need for fast and comprehensive characterization of biocatalysts has pushed the development of new screening platforms based on microfluidics, capable of monitoring several parameters simultaneously, with new configurations of liquid handling, sample treatment and sensing. Modular microfluidics allows the integration of these newly developed approaches in a more flexible way towards increasing applicability of the microfluidic chips to different types of biocatalysts and reactions. A highly relevant operation in such a system is biocatalyst inactivation, which can enable the precise control of reaction time by avoiding the continuation of the reaction in another module or connecting tubes. Such control is important when different modules of reactors and/or sensing units are used and changed frequently. Here we describe the development, characterization and application of a module for rapid enzyme inactivation. The thermal inactivation platform developed is compared with a standard benchtop ThermoMixer in terms of inactivation efficiency for glucose oxidase and catalase. A higher activity loss was observed for enzyme inactivation under flow conditions (inactivation achieved at 120 s residence time at 338 K and 20 s residence time at 353 K) which indicated a high heat transfer to the fluid under dynamic conditions. Moreover, partial deactivation of the enzymes was observed for the continuous thermal inactivation module, when activity measurements were performed after 1 and 2 days following inactivation. The thermal inactivation unit presented can be easily integrated into modular microfluidic platforms and can be a useful addition for enzyme characterization and screening.

Evaluation of WO2014121383 A1: a process for preparation of rufinamide and intermediates

INTRODUCTION

There is great potential in the synthetic development of rufinamide to treat childhood-onset epilepsy known as Lennox-Gastaut syndrome (LGS). Areas covered: 1,4-disubstituted triazole ring formed by 1,3-dipolar cycloaddition reaction is an important structural motif widely used to construct diverse chemotypes in chemical, biological, and material fields. 1,2,3-triazole ring containing rufinamide, an antiepileptic drug developed by Novartis, is useful in combination with other antiepileptic medicaments for the treatment of childhood-onset epilepsy known as LGS. There are numerous synthetic methods used to construct the rufinamide through 1,3-dipolar cycloaddition. The application claims processes for the preparation of rufinamide and their intermediates. The synthetic strategy covered for the synthesis of rufinamide using activated acetylenic esters. The activation is done using N-hydroxy succinimide, N-hydroxyphthalimide, 1-hydroxy benzotriazole, and 4-nitro phenol. Expert opinion: The manufacturing route appears to follow the regioselective Cu catalyzed cycloaddtion of 2,6-difluro benzyl azide with or without isolated activated acetylenic esters in three steps that provide a good lead for new synthetic strategy for the rufinamide synthesis.

Asymmetric phosphoric acid-catalyzed four-component Ugi reaction

The Ugi reaction constructs α-acylaminoamide compounds by combining an aldehyde or ketone, an amine, a carboxylic acid, and an isocyanide in a single flask. Its appealing features include inherent atom and step economy together with the potential to generate products of broad structural diversity. However, control of the stereochemistry in this reaction has proven to be a formidable challenge. We describe an efficient enantioselective four-component Ugi reaction catalyzed by a chiral phosphoric acid derivative that delivers more than 80 α-acylaminoamides in good to excellent enantiomeric excess. Experimental and computational studies establish the reaction mechanism and origins of stereoselectivity.

Recent Advances and Perspectives in Cancer Drug Design

Cancer is one of the leading causes of death worldwide. With the increase in life expectancy, the number of cancer cases has reached unprecedented levels. In this scenario, the pharmaceutical industry has made significant investments in this therapeutic area. Despite these efforts, cancer drug research remains a remarkably challenging field, and therapeutic innovations have not yet achieved expected clinical results. However, the physiopathology of the disease is now better understood, and the discovery of novel molecular targets has refreshed the expectations of developing improved treatments. Several noteworthy advances have been made, among which the development of targeted therapies is the most significant. Monoclonal antibodies and antibody-small molecule conjugates have emerged as a worthwhile approach to improve drug selectivity and reduce adverse effects, which are the main challenges in cancer drug discovery. This review will examine the current panorama of drug research and development (R&D) with emphasis on some of the major advances brought to clinical trials and to the market in the past five years. Breakthrough discoveries will be highlighted along with the medicinal chemistry strategies used throughout the discovery process. In addition, this review will provide perspectives and updates on the discovery of novel molecular targets as well as drugs with innovative mechanisms of action.

N1-Selective alkenylation of 1-sulfonyl-1,2,3-triazoles with alkynes via gold catalysis

A N¹-selective alkenylation of 1-sulfonyl-1,2,3-triazoles with alkynes via gold catalysis is reported. N¹-Vinyl substituted 1,2,3-triazoles were selectively prepared in up to 92% yield through the sulfonyl group of 1,2,3-triazole derivatives transformed to alkenyl groups in a "one-pot two steps" manner. This method provided a new method for the synthesis of potentially biological-active vinyl-triazole building blocks.

Design and synthesis of a new series of 3,5-disubstituted isoxazoles active against Trypanosoma cruzi and Leishmania amazonensis

Chagas disease and leishmaniasis are neglected tropical diseases (NTDs) endemic in developing countries. Although there are drugs available for their treatment, efforts on finding new efficacious therapies are continuous. The natural lignans grandisin (1) and veraguensin (2) show activity against trypomastigote T. cruzi and their scaffold has been used as inspiration to design new derivatives with improved potency and chemical properties. We describe here the planning and microwave-irradiated synthesis of 26 isoxazole derivatives based on the structure of the lignans 1 and 2. In addition, the in vitro evaluation against culture trypomastigotes and intracellular amastigotes of T. cruzi and intracellular amastigotes of L. amazonensis and L. infantum is reported. Among the synthesized derivatives, compounds 17 (IC₅₀ = 5.26 μM for T. cruzi), 29 (IC₅₀ = 1.74 μM for T. cruzi) and 31 (IC₅₀ = 1.13 μM for T. cruzi and IC₅₀ = 5.08 μM for L. amazonensis) were the most active and were also evaluated against recombinant trypanothione reductase of T. cruzi in a preliminary study of their mechanism of action.

N-2-Selective gold-catalyzed alkylation of 1-sulfonyl-1,2,3-trizoles

An efficient new method was developed to synthesis N-2-alkyl-1,2,3-trizoles via gold catalyzed alkylation of 1-sulfonyl-1,2,3-trizoles with vinyl ethers.