U.S. FDA Approved Drugs from 2015-June 2020: A Perspective

Anti-Inflammatory Furylidene Tetronic Acid Derivatives from an Endophytic Fungus Hypoxylon monticulosum ZZ14

Naturally occurring furylidene tetronic acids were rare and structurally unique, typically with a furylidene connected to a furan-2,4-(3H, 5H)dione (tetronic acid moiety). In the current study, seven furylidene tetronic acid derivatives (1-7) were isolated and identified from the endophytic fungus Hypoxylon monticulosum ZZ14, including three new ones, hypoxytetronic acids A and B (1 and 2) and 2',3'-dihydronodulisporacid A methyl ester (3). Compounds 1 and 2 possess an unusual skeleton, with two tetrahydrofurans attached to the tetronic acid moiety. Their absolute configurations were elucidated by custom-DP4+ probability analysis of NMR chemical shifts and ECD calculations. Nodulisporacid A methyl ester (7) significantly inhibited the production of interleukin 6 (IL-6), interleukin 10 (IL-10), nitric oxide (NO), and inducible nitric oxide synthase (iNOS), comparable to the positive control dexamethasone. Several analogues of nodulisporacid A methyl ester were synthesized, and structure-activity relationship studies were performed, suggesting that the conjugated fragment of 1/2/3/1'/2'/3' and the methyl ester group may be the pharmacophores.

General Approach To Access Aldehyde Oxidase Metabolites of Drug Molecules via N-Oxidation/Reissert-Henze-Type Reaction

Aldehyde oxidase (AO) contributes significantly to metabolism of drug molecules containing heteroaromatics, and the lack of synthetic mimics for AO-mediated reactivity is a barrier to drug development. Herein, we use tandem N-oxidation and Reissert-Henze-type reaction of quinoline and related heteroaromatics to form quinolone derivatives. This reactivity is showcased with small molecule building blocks and active pharmaceutical ingredients with known AO metabolism. The products of the latter substrates map directly onto established AO metabolites.

Accessing sulfonamides via formal SO2 insertion into C-N bonds

Functional group interconversions are particularly sought after by medicinal chemists as a means to enable both lead optimization and library diversification. Here we report SO2 insertion into the C-N bond of primary amines, enabling the direct synthesis of primary sulfonamides without preactivation and effectively inverting the nitrogen's properties (acidity, hydrogen bonding and so on). The key to this transformation is the implementation of an anomeric amide as a dual-function reagent that both serves to cleave the initial C-N bond and delivers a nitrogen atom to the product after SO2 incorporation. The process tolerates a wide array of functionalities and can be run in an automated fashion, thus allowing libraries of amines to be viable progenitors to highly desirable sulfonamides. Mechanistic studies support an isodiazene radical chain mechanism that generates an intermediate sulfinate that reacts with the anomeric amide to forge the S-N bond. Our protocol was used to conduct a high-throughput library diversification campaign, was applied to the synthesis and modification of approved active pharmaceutical ingredients and was used to enable a net CO-to-SO2 isosteric replacement approach.

A Predictive Model for Thiol Reactivity of N-Heteroaryl α-Methylene-γ-Lactams─A Medicinally Relevant Covalent Reactive Group

Herein, we present a systematic study on the effects of electronically diverse heteroarenes on the rate of glutathione (GSH) addition to novel N-heteroaryl α-methylene-γ-lactam covalent reactive groups (CRGs). Despite their unique electronic and drug-like properties, heteroarenes have not been extensively studied as handles for systematically tuning the reactivity of CRGs. Informed by mechanistic insights, we evaluated 16 substrate parameters, including a new heteroaryl Hammett-type substituent constant (σHet), for their correlation with experimental reactivity (ΔG‡exp) as determined by 1H NMR kinetic studies. Of these parameters, electron affinity represents a robust single-parameter predictive model of CRG reactivity with thiols, as demonstrated by test sets of additional N-heteroaryl lactams (MUE = 0.4 kcal/mol) and other α,β-unsaturated amide CRGs (MUE = 0.3 kcal/mol). These N-heteroaryl lactams were subsequently shown to inhibit cysteine protease activity (i.e., papain enzyme) to varying degrees that correlate with both the experimentally observed and predicted reactivity with GSH.

Photochemical C3-amination of pyridines via Zincke imine intermediates

Selective skeletal and peripheral editing of the pyridine moiety has broadly expanded the chemical space. While C-H functionalization at C2 and C4 positions are enabled by the inherent reactivity of this heteroarene, selective derivatization at the C3 position has long posed a significant challenge. Recently, based on a dearomatization-rearomatization sequence, involving Zincke imine intermediates, selective halogenation (-Br, -Cl, and -I) and isotopic labelling were accomplished. Here, we report a mild and regioselective method for C3-amination that relies on the photochemical reaction of Zincke imine with an amidyl radical generated from N-aminopyridinium salts. Mechanistic and theoretical studies indicate that radical intermediates are involved and explain the C3 regioselectivity of the reaction.

A modular, reusable biocatalytic flow system for UDP-GlcNAc production

We report here the continuous flow synthesis of a high-value sugar nucleotide. Immobilisation of enzymes onto solid carriers permitted transfer of the biocatalysts into packed bed reactors to realise a continuous biocatalytic platform for the synthesis of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) on 100 mg scale, with capacity for multiple reuses. The modular continuous flow approach described here represents a significant, up to 11-fold, improvement in space time yield (STY) when compared to batch studies, along with preventing product induced enzyme inhibition, reducing the need for an additional enzyme to break down inorganic pyrophosphate (PPi). The modular nature of the system has also allowed tailored conditions to be applied to each enzyme, overcoming issues relating to thermal stability. This development presents a platform approach towards a more efficient, continuous synthesis of important glycan targets including glycoproteins, specific oligosaccharide sequences and glycosylated drug targets.

C3-H Trifluoroacetylation of Quinolines and Pyridines: Access to Heteroaryl Ketones, Carboxylic Acids, and Amides

Despite extensive synthetic endeavors, achieving direct C3-H trifluoroacetylation in quinolines/pyridines continues to pose significant challenges. We report a protocol for direct C3-H trifluoroacetylation of quinolines and pyridines under transition-metal-free conditions. Readily accessible quinolines or pyridines serve as starting materials and undergo a dearomatization process to generate dihydroquinoline or dihydropyridine intermediates, which readily react with trifluoracetic anhydride. Subsequent acid-promoted dealkylative rearomatization delivers heteroaryl trifluoromethyl ketones. This tandem process is accomplished in a two-pot, one column process. The trifluoroacetyl group in the resulting heteroarenes can be readily transformed into a variety of functional groups.

Deciphering the electronic structure and conformational stability of 2-pyridinecarboxaldehyde

The conformational structures and ionisation dynamics of 2-pyridinecarboxaldehyde (2-PCA) were explored using high-resolution vacuum ultraviolet mass-analysed threshold ionisation (VUV-MATI) spectroscopy, complemented by Franck-Condon (FC) simulations and quantum chemical calculations. The precise adiabatic ionisation energy of 2-PCA was determined to be 76 589 ± 4 cm-1 (9.4958 ± 0.0005 eV), which is notably lower than the previous values obtained from electron impact ionisation studies. The vibrationally resolved VUV-MATI spectrum of the molecule confirmed that ionisation predominantly originates from its s-trans conformer, with no significant contribution from its s-cis conformer, indicating that the interconversion barrier effectively limits the population of this species under supersonic expansion conditions. Molecular and natural bond orbital analyses revealed that the highest occupied molecular orbital of the s-trans conformer is primarily composed of a nitrogen nonbonding orbital, which interacts with the oxygen lone pairs of the formyl group. This interaction stabilises the electronic structure of the conformer, resulting in an increased ionisation energy compared with pyridine. FC analysis further demonstrated that vibrational excitations in the cationic state are predominantly associated with the in-plane ring and formyl bending modes, producing distinct vibrational progressions in the VUV-MATI spectrum. These findings provide not only valuable insights into the electronic structure, conformational stability, and ionisation dynamics of 2-PCA, but also a deeper understanding of the effect of functional-group substitution in pyridine derivatives. Moreover, the results underscore the effectiveness of VUV-MATI spectroscopy in resolving conformer-specific ionisation processes, paving the way for further investigations into the electronic properties of heterocyclic molecules.

Iron-Catalyzed Alkylative Aminosulfonylation of Alkenes and Alkynes via Radical-Anion Relay

A novel Fe-catalyzed alkylative aminosulfonylation of alkenes and alkynes with alkyl halides and O-Ts activated hydroxylamines by using Na2S2O4 as a reductant and sulfone source has been developed. The metal-electron-shuttle catalysis was discovered to be vital for the highly efficient generation of sulfonyl radicals and anions without requiring organometallic intermediates. This method provides efficient access to sulfonamides from easily available alkenes and Na2S2O4 and features a broad substrate scope.

Visible-Light-Mediated Copper-Catalyzed S-Arylation of Sulfenamides with Aryl Thianthrenium Salts

The site-selective incorporation of sulfilimine functionalities into aromatic compounds provides a vital strategy for drug discovery in medicinal chemistry. However, green and sustainable methods for realizing the goal are still limited. Here, we report a copper-catalyzed S-arylation of sulfenamides with aryl thianthrenium salts irradiated by visible light without the photocatalyst, which exhibited fine functional-group compatibility and gave the desired products in high yields. Mechanistic investigations revealed that the key to achieving these results is the generation of an electron donor-acceptor (EDA) complex between sulfenamides and aryl thianthrenium salts under basic conditions.

Diastereoselective Radical Cyclization of Imine and Olefin: Rapid Access to 1,2,3,4-Tetrahydroquinoline Scaffolds

Herein, we developed an intramolecular radical cyclization reaction between imines (or aldehydes) and olefins using Hantzsch ester as the reductant to enable the efficient and diastereoselective synthesis of 1,2,3,4-tetrahydroquinoline scaffolds with a high medicinal value. Deuteration experiments indicated that the radical intermediate abstracts a hydrogen atom directly from the 4 position of the Hantzsch ester, thereby ruling out the possibility of an anionic intermediate formation via the radical crossover pathway. A fast synthesis of BRD4 degraders and the elucidation of their cellular and enzymatic activities demonstrate the practicality of this method.

Recent advances in the synthesis of bicyclo[4.1.1]octanes

The exploration of bicyclo[n.1.1]alkanes, known for their intricate chemical diversity and potential as benzene bioisosteres, has garnered significant attention over the past two decades. In particular, the past year has seen the emergence of bicyclo[4.1.1]octanes and their structural analogues as promising bioisosteres for meta-substituted arenes and cis-1,3-disubstituted cyclohexanes. To meet the growing demand for bicyclo[4.1.1]octanes, chemists have recently developed innovative (4 + 3) cycloaddition strategies, leveraging bicyclobutanes (BCBs) and 1,4-dipoles for their synthesis. This review provides a comprehensive evaluation of recent advancements in the synthesis and functionalization of these compounds, emphasizing their scope and underlying mechanisms. Additionally, we highlight the challenges and future prospects of identifying novel reaction pathways to access new functionalized bicyclo[4.1.1]octanes.

Visible light-promoted cascade synthesis of pyrazolidinones via N-aryl glycine and azomethine imines

We present an effective, visible light-driven method for the synthesis of N-(β-amino)pyrazolidin-3-ones from N-aryl glycine and azomethine imines. This additive-free protocol utilizes blue light (λmax = 435-445 nm) at room temperature, enabling a radical-mediated cascade reaction that delivers a diverse range of pyrazolidinones in yields up to 99%. The mild conditions, high efficiency, and broad substrate scope of this process make it an attractive strategy for streamlined synthesis in drug discovery and material science.

The metal(loid)s' dilemma. What's the next step for a new era of inorganic molecules in medicine?

In this paper, we critically examine the key challenges associated with the development of inorganic drugs, a field that remains underrepresented despite its significant therapeutic potential. Currently, most clinically approved pharmaceuticals are organic compounds, a trend driven by multiple interconnected factors that have historically limited the adoption and regulatory approval of metal(loid)-based entities. These challenges include issues related to stability, selectivity, pharmacokinetics, and potential toxicity, which require systematic investigation and innovative solutions. Nevertheless, the profound clinical impact of approved inorganic drugs-particularly transition metal(loid)-based agents for both therapeutic and diagnostic applications-is well-established. The success of these compounds underscores the need for expanded research efforts and optimized clinical protocols to fully harness the advantages of metal-based pharmaceuticals. In this context, we explore emerging strategies to overcome current limitations and accelerate the development of next-generation inorganic drugs. These include the rational design of metal-based therapeutics, the integration of advanced metallomics and metalloproteomics, and the application of AI-driven predictive modeling to improve drug selectivity, bioavailability, and safety. By overcoming these challenges through an interdisciplinary approach, metal-based medicine will advance significantly, expanding its impact across a wide range of therapeutic applications.

In-depth understanding of the structure-based reactive metabolite formation of organic functional groups

Idiosyncratic drug-induced liver injury (DILI) is a leading cause of drug attrition and/or withdrawal. The formation of reactive metabolites is widely accepted as a key factor contributing to idiosyncratic DILI. Therefore, identifying reactive metabolites has become a critical focus during lead optimization, and a combination of GSH-/cyano-trapping and cytochrome P450 inactivation studies is recommended to identify compounds with the potential to generate reactive metabolites. Daily dose, clinical indication, detoxication pathways, administration route, and treatment duration are the most considerations when deprioritizing candidates that generate reactive metabolites. Removing the structural alerts is considered a pragmatic strategy for mitigating the risk associated with reactive metabolites, although this approach may sometimes exclude otherwise potent molecules. In this context, an in-depth insight into the structure-based reactive metabolite formation of organic functional groups can significantly aid in the rational design of drug candidates with improved safety profiles. The primary goal of this review is to delve into an analysis of the bioactivation mechanisms of organic functional groups and their potential detrimental effects with recent examples to assist medicinal chemists and metabolism scientists in designing safer drug candidates with a higher likelihood of success.

Design and development of new substituted pyrimidine hybrids with imidazole and triazole: Exploring utility as an anticancer agent via human topoisomerase-II and tubulin inhibition

In the present research, we developed pyrimidine-based hybridized molecules with either imidazole or triazole to find effective anticancer drugs. The reaction was accomplished using a multicomponent reaction pathway. The synthetics were explored for their utility as an anticancer agent via human topoisomerase-II and tubulin inhibition. Among the synthetics, compounds 1B4, 1B5, and 1B6 were potent anticancer agents tested in five cancer cell lines compared to colchicine and etoposide employed as positive controls. These synthetics were found further devoid of any significant cytotoxicity towards normal cells, thus proving their selective anticancer nature. Further, these compounds inhibited both the tubulin and hTopoII as indicated by in vitro-based assay. The mechanistic insights were corroborated using molecular docking studies. Besides this, the molecules were found to portray their secondary anticancer cell death mechanism via apoptosis. They decreased the oxidative stress, induced apoptosis, and arrested the cell cycle arrest at the G2/M phase in cancer cells.

Fluorine in the Pharmaceutical Industry: FDA-Approved Fluorine-Containing Drugs in 2024

Fluorine has become an essential element in the development of modern pharmaceuticals, due to its unique chemical properties that can significantly enhance the biological activity, metabolic stability, and lipophilicity of drug molecules. This review explores recent advancements in the synthesis and application of fluorine-containing drugs approved by the US Food and Drug Administration (FDA) in 2024. These novel drugs demonstrate improved efficacy and safety profiles, addressing a range of therapeutic areas including oncology, infectious diseases, metabolic disorders and genetic disorders that affect the adrenal glands. The incorporation of fluorine atoms into drug candidates has facilitated the development of molecules with optimized pharmacokinetic and pharmacodynamic properties, leading to better patient outcomes. The review further discusses the synthetic methodologies employed, the structural characteristics of these drugs, and their clinical implications, providing insights into the ongoing innovation within the pharmaceutical industry driven by fluorine chemistry.

Water-Stable 2-Pyridylboron Reagents: Pd-Catalyzed 2-Pyridylation Reaction of Aryl Halides

The stability of 2-pyridylation reagents is a long-standing issue in cross-coupling chemistry due to hydrolysis. However, as the use of pyridine-based pharmaceuticals continues to increase, there is a high demand for stable and reactive 2-pyridylation reagents. Herein, a general strategy to prepare water-stable 2-pyridylboron reagents has been developed. The application of the water-stable 2-pyridylboron reagents in a neutral Suzuki-Miyaura coupling with a halide scavenger enables an efficient 2-pyridylation reaction of aryl halides.

Systematic Investigation of CYP3A4 Using Side-by-Side Comparisons of Apo, Active Site, and Allosteric-Bound States

Cytochrome P450 (CYP) 3A4 (CYP3A4) is a complex enzyme that metabolizes diverse substrates. It contains a large binding site accommodating diverse ligands, binding to active or allosteric sites. CYP3A4 does not always follow Michaelis-Menten kinetics. While Km reflects substrate affinity, it does not necessarily determine the enzyme's activity, though it is often considered indicative of substrate binding characteristics. The mechanism may be highly sophisticated and driven by multiple factors. This suggests that the ligand binding affinity alone may not explain the differential behavior of the enzyme conformational stability. Here, we analyzed sequence conserveness of 57 CYPs, followed by a detailed molecular dynamics simulation study (9 μs) on CYP3A4. We studied three CYP3A4 enzyme states (apo-state, active-site, and allosteric-site ligand-bound states) collected from the same experimental setup to reduce the systematic error. We found that the enzyme conformational stability followed a consistent trend of allosteric > active > apo states, which was inconsistent with the enzyme-ligand (active/allosteric) binding affinity and the ligand conformational stability. However, the heme group showed a significant protein affinity and stability pattern directly related to the enzyme stability, suggesting that the active/allosteric binding may work by influencing the heme-CYP3A4 binding affinity, and the allosteric ligand appeared to form the most stable enzyme state of the three studied states.

Synthesis of Indazole Fused 2-Benzazepines with Polarity-Dependent Fluorescence Based on Formal [4 + 3] Annulation of 3-Aryl-1H-indazoles with Cyclopropenones

The effective assembly of benzazepine skeletons in a sustainable and atom-economical fashion remains a challenging goal in modern organic synthesis. Presented herein is a novel synthesis of indazole fused 2-benzazepine derivatives based on a formal [4 + 3] annulation of 3-aryl-1H-indazoles with cyclopropenones. The formation of products proceeds through Ir(III)-catalyzed aryl C-H bond metalation and cyclopropenone ring-opening leading to aryl acylation, followed by an intramolecular N-nucleophilic conjugated addition. By using this method, a number of valuable benzazepine derivatives were effectively generated. This protocol addresses the challenges in constructing medium-sized rings through cascade C-H/C-C bond activation and C-C/C-N bond formation. Moreover, the photophysical properties of the products thus obtained were also evaluated. It turned out that all compounds tested showed solvent polarity-dependent fluorescence features, which could be potentially applied for revealing the polarity of their immediate environments.

Heterocycle-based dynamic covalent chemistry for dynamic functional materials

Dynamic covalent chemistry, which renders reusable and degradable thermoset polymers, is a promising tool for solving the global problem of plastic pollution. Although dynamic covalent chemistry can construct dynamic polymer networks, it rarely introduces other functions into polymers, which limits the development of dynamic functional materials. Herein, we develop heterocycle-based dynamic covalent chemistry and demonstrate the reversibility of the aza-Michael addition reaction between functional heterocycle dihydropyrimidin-2(1H)-thione and electron-deficient olefins. Our method produces a degradable linear polymer and recyclable and self-healable crosslinked polymers similar to traditional dynamic covalent chemistry, but the heterocycles endow the polymer with excellent ultraviolet-blocking and high-energy blue light-blocking abilities, and tunable fluorescence and phosphorescence properties. These are difficult to create with ordinary dynamic covalent chemistry. This proof-of-concept study provides insights into heterocycle-based dynamic reactions, and may prompt the development of dynamic chemistry and dynamic functional materials.

Enhanced Regioselectivity Prediction of sp2 C-H Halogenation via Negative Data Augmentation and Multimodel Integration

Efficient molecular editing is pivotal in synthetic chemistry, especially for developing drugs, materials, and high-value chemicals. Electrophilic aromatic substitution (SEAr) reactions, specifically sp2 C-H halogenation, face significant challenges due to electronic and steric factors, necessitating extensive trial-and-error. This study introduces an innovative machine learning-based model to predict halogenation sites in SEAr reactions, achieving an average accuracy of 93% in 5-fold cross-validation. Employing ensemble techniques, particularly AutoGluon-Tabular (AG), the model demonstrates broad applicability across various aromatic halides, enhancing its utility in drug design, materials science, and more. By reducing experimental uncertainty and optimizing synthetic pathways, this model saves considerable time and resources, thereby accelerating innovation in synthetic chemistry.

Cyclic Diphenylchloronium-Salt-Triggered Coupling of Sulfides with Nucleophiles: Modular Assembly of Pharmaceuticals

We report a novel coupling strategy enabled by cyclic diphenylchloronium salt that facilitates reactions between sulfides and diverse nucleophiles, including oxygen- and nitrogen-based species. The methodology efficiently produces structurally varied valuable compounds, including carbamates, carboxylic esters, aryl ethers, and alkylated amines, under mild, operationally simple conditions. The protocol's synthetic utility was highlighted through modular preparation of five important drugs and five structural analogues, demonstrating significant potential for drug discovery applications.

Synthesis of 2,5-Dithia-bicyclo[4.1.1]octanes by Silver-Catalyzed Formal (4+3) Cycloadditions of Bicyclobutanes with Benzodithioloimines

Cycloadditions of bicyclobutanes with two- or three-atom reaction partners have been widely exploited to access bicyclo[2.1.1]hexanes and bicyclo[3.1.1]heptanes. However, their application to the synthesis of bicyclo[4.1.1]octane derivatives has remained elusive. Herein, we report silver-catalyzed formal (4+3) cycloadditions between simple bicyclobutanes and benzodithioloimines, establishing a new method for synthesizing previously inaccessible 2,5-dithia-bicyclo[4.1.1]octanes, which have two sulfur atoms in their bicyclo[4.1.1]octane frameworks. This mild method tolerates bicyclobutane substrates with a wide range of substituents. The synthetic utility of this method was demonstrated via various synthetic transformations of the products to yield valuable sulfur-containing bridged bicyclic scaffolds.

Tandem Azolation/Aromatization of Tetrahydronaphthalenes with Hydrogen Evolution via Organophotoredox/Cobalt Dual Catalysis

Reported herein is a photoredox/cobaloxime dual-catalytic approach to execute tandem dehydrogenative azolation and aromatization of tetrahydronaphthalene for rapid construction of N-(β-naphthyl)azole architectures. This protocol highlights noble metal-free and external oxidants-free conditions, step- and atom-economy, and site-selectivity. A preliminary mechanistic study has uncovered that the transformation undergoes a N-centered radical mediated C-H/N-H cross-coupling followed by dehydrogenative aromatization of saturated naphthyl surrogates under visible light irradiation, and DFT calculations elucidate the site-selectivity.

N-Heterocyclic Carbene Organocatalysis Enabled Modular Synthesis of Fluorinated Isoflavonoids to Suppress Proliferation and Migration in Breast Cancer Cells

Isoflavonoids represent a privileged scaffold among various bioactive natural products, rendering their structural diversification through green synthesis and subsequent biological evaluations a compelling research area. In this study, an NHC organocatalytic radical acylalkylation of 1,3-enynes using salicylaldehydes is presented, followed by a cascade intramolecular annulation, yielding a series of fluorinated isoflavone derivatives with substantial yields under environmental-friendly conditions. This approach, distinguished by its excellent modularity and high functional group tolerance, represents an unprecedented organocatalytic 1,3,4-trifunctionalization of 1,3-enynes designed for the green synthesis of bioactive isoflavones in a single step. Furthermore, it is demonstrated that these synthesized fluorinated isoflavonoids effectively suppress proliferation in breast cancer cells, with the most potent compound 8 also inhibiting migration in MDA-MB-231 cells.

Modular Synthesis of 3,3-Disubstituted Azetidines via Azetidinylation Reagents

Azetidines represent an attractive and emerging design option in medicinal chemistry owing to their small size and polar nature, as well as their potential to significantly impact the physicochemical properties of drug molecules. However, traditional methods for the synthesis of 3,3-disubstituted azetidines usually require higher step counts or exhibit poor functional group compatibility. Herein, we report a modular synthesis strategy for 3,3-disubstituted azetidines based on azetidinylation reagents. The practicality of this method is further exemplified by the use of readily available starting materials, mild reaction conditions, and a very broad substrate scope.

Platform of Oxidative Transformation of α-Methyl Secondary Enaminones toward Tetrahydropyridines

In this paper, the application of α-methyl secondary enaminones in the synthesis of tetrahydrofuropyridines is described. The key step of the methodology is the in situ generation of 1-azadiene from oxidation of α-methyl secondary enaminone, followed by a subsequent inverse-electron-demand hetero-Diels-Alder reaction proceeded to give the desired product. Mechanistic studies and density functional theory (DFT) calculations revealed the detailed reaction pathway. Gram-scale preparation experiments and further transformation of the product demonstrate the potential applicability of this method. In addition, the amide derivatives could be obtained by employing β-methyl secondary enaminones as substrates under similar oxidative conditions. The present work opens a new window to the application of rarely reported α-methyl secondary enaminones.

Construction of Benzoxazole and Isoquinoline Compounds via Base-Mediated Cyclization of Amino Acid Derivatives

Biological organisms contain bioactive macromolecules such as amino acids, which serve as basic materials for constructing cells and repairing tissues. Due to the unique properties of the fluorine atom, which can alter the structure of proteins and increase their lipophilicity, incorporating a fluorine atom into amino acids has become a research hotspot. In this study, ethyl 3-bromo-2-((diphenylmethylene)amino)-3,3-difluoropropanoate was synthesized from glycine derivatives. Under alkaline conditions, this compound reacted with 2-aminophenol to generate a benzoxazole-containing amino acid derivative. This method is simple to operate, without metal participation, and is performed under relatively eco-friendly reaction conditions, providing a novel approach for the synthesis of benzoxazole heterocycles.

The Long Arc of Substance Use Policy Innovation in Medicaid: Looking Back, Looking Forward

Policy Points The role of Medicaid in financing, organizing, and delivering substance use disorder (SUD) treatment has grown tremendously over time owing to expansions of eligibility and a push toward more uniformity in benefits. Current innovations in SUD treatment focus on expanding the delivery system to create a comprehensive continuum of care, using more value-based payment to reward quality care, and integrating SUD treatment with other systems (e.g., housing, employment, and the criminal legal system). Many of the promising innovations in delivery have not yet been rigorously studied, and implementation of effective models is often stymied because of the lack of flexibility in program requirements and variation in needs and resources across communities. Although policymakers can justifiably laud the great strides Medicaid has made in raising the standards for SUD treatment, there is a huge remaining gap in access to services amidst an unprecedented overdose crisis and looming turmoil in the program.

Silver-mediated formal [4π + 2σ] cycloaddition reactions of bicyclobutanes with nitrile imines: access to 2,3-diazobicyclo[3.1.1]heptenes

Despite recent advances in the synthesis of aza-bicyclo[3.1.1]heptanes (aza-BCHeps, which have an sp3-hybridized nitrogen atom) and azabicyclo[3.1.1]heptenes (aza-BCHepes, which have an sp2-hybridized nitrogen atom), which are bioisosteres of pyridine, construction of 2,3-diazobicyclo[3.1.1]heptenes (2,3-diazo-BCHepes), which have both sp2- and sp3-hybridized nitrogen atoms, has yet to be achieved. Herein, we disclose a method for silver-enabled formal [4π + 2σ] cycloaddition reactions between bicyclobutanes and nitrile imines (generated from hydrazonyl chlorides) to furnish a diverse array of 2,3-diazo-BCHepes, which feature both sp2- and sp3-hybridized nitrogen atoms embedded in a BCHepe framework. These compounds have the potential to serve as bioisosteres of both pyridines and pyridazines. Owing to the presence of the sp3-hybridized nitrogen, 2,3-diazo-BCHepes can be expected to exhibit geometries similar to those of aza-BCHepes and much better solubility. We demonstrated the synthetic utility of our method by carrying out a scaled-up reaction and diverse postcatalytic transformations.

Exploring USFDA-Approved Imidazole-Based Small Molecules in Drug Discovery: A Mini Perspective

In the present work, we have explored the importance of the imidazole ring and its importance in drug discovery, citing the key approvals in the present decade (2013-2024). The pharmacological attribution for the approved drugs revealed that out of 20 approved drugs, 45% of the approvals were made as anti-infectives, followed by approvals under the category of genetic and metabolic disorders, sexual endocrine disorders, anticancer, and to treat blood pressure, gastrointestinal disorders, and neurological conditions. Most approved drugs were dispensed through solid dosage forms (13) and thus had predominantly oral routes beside others. The metabolism pattern revealed that the drugs undergo metabolism via the involvement of multiple enzymes, where CYP3A4 and CYP3A5 were the core enzymes. The excretion pattern of these drugs revealed that the drugs are majorly excreted via the fecal route. The chemical analysis showed that pyrrolidine/pyrrole was the major heterocycle in the approved drugs, followed by the indole ring in the hybridization. Considering the substitution pattern, most drugs possessed amide, amines, and fluoro group as the functional substitution with the 2,4-substitution pattern seen in most approved drugs. Besides this, the three approved drugs were found to possess chiral centers and exhibit chirality. The article also expanded to cover the synthetic routes and metabolic routes for this versatile ring system and case studies for its utility to serve as bioisostere in drug discovery. Furthermore, this article also presents the receptor-ligand interactions of imidazole-based drugs with various target receptors. The present article is, therefore, put forth to assist medicinal chemists and chemists working in drug discovery of this versatile ring system.

Rapid C-S Coupling in Water via Ion-Pair-Catalyzed Dehydration

The C-S bond is of significant importance due to its unique properties and diverse roles in chemistry, biology, and materials science. In this work, we present an efficient synthetic protocol of a rapidly dehydrative C-S coupling reaction with alcohols and thiols in water catalyzed by a triaryl-carbenium ion pair. Under metal-free conditions, a wide range of thioethers were obtained in good yields (up to 99%) with excellent functional group tolerance, including the fast modification of amino acid derivatives and functional molecules. This method allowed reactions to be conducted with low catalyst loading, down to 1.0 mol %, and was practical for gram-scale synthesis. Furthermore, the reactions were performed under biocompatible conditions, making this approach highly suitable for potential bioconjugation.

High Selectivity Hydroxylation and Other Functionalization of Quinoline-Directed Reactions under Cu(II)-Catalysis

Despite progress in ortho C-H functionalization of aromatic rings directed by guiding groups, achieving highly selective hydroxylation in simple systems without the need for additional ligand assistance remains a significant challenge. Here, we report the direct hydroxylation of the ortho C-H bond of aromatic rings directed by quinoline under Cu(II) catalysis. Based on experimental analysis and DFT calculations, the main reason for the high selectivity of the quinoline-directed hydroxylation reaction is that the match between the new substrate and the method leads to an increased range of oxygen source incorporation. Isotope experiments and DFT calculations provide support for the origin of the oxygen source in the hydroxylation process and the rationale behind its observed distribution. Additionally, the introduction of various nucleophiles enabled the cyanation, nitration, and halogenation of ortho C-H bonds in the aryl group.

An expedient ruthenium(II) catalyzed multicomponent access to phthalazinones bearing trisubstituted alkenes

Nitrogen based heterocycles bearing trisubstituted alkenes are prodigious and indispensable motifs in pharmaceuticals, clinical candidates and functional materials. Herein, we developed a tandem one-pot ruthenium-catalyzed multicomponent reaction to access phthalazinones bearing trisubstituted alkenes by employing readily available hydrazines, 2-formyl-benzoic acid and alkynes. The key highlights of this work are its atom economy and greenness, with water as the only byproduct. This reaction exhibits high functional group tolerance and is also scalable to gram-scale synthesis. Remarkably, the current protocol is applied to a four-component reaction involving in situ nitro reduction by utilizing TFE (2,2,2-trifluoroethanol) as a liquid hydrogen carrier, along with imine formation and esterification. A series of control experiments were conducted to elucidate the reaction mechanism. Importantly, the possible intermediates were confirmed by mass spectrometry. Moreover, the products obtained show strong emission properties that are aligning well with DFT calculations.

meta-Nitration of Pyridines and Quinolines through Oxazino Azines

meta-Nitration of azines (pyridines and quinolines) serves as a powerful method for the prompt construction and derivatization of several pharmaceuticals, agrochemicals, and materials. However, due to the inherent electronic properties of pyridines, achieving direct selective meta-C-H nitration under mild conditions has been a long-standing challenge in synthetic chemistry. Currently, there is no adequate strategy for late-stage meta-C-H nitration of pyridine-containing drugs and drug precursors. To address this void, we introduce a practical protocol for the highly regioselective meta-nitration of pyridines using a dearomatization-rearomatization strategy. The introduced method provides a diversification platform for selective nitration at the meta-position of azines via a radical pathway. This mild, open-air, one-pot, scalable, and catalyst-free process is employed for the late-stage meta-nitration of pyridine containing drugs, drug precursors, and ligands using pyridines as the limiting reagents. Consecutive C3 and C5 difunctionalization of pyridines is also achieved with complete regiocontrol relying on sequential addition, which further highlights the potential of the presented work. Additionally, the obtained products could be transformed into meta-amino azine products and other valuable building blocks. Incorporating N-heterocyclic amine structures through amidation into ibuprofen has significantly improved the drug's clinical success, highlighting the importance of this work.

Design, synthesis, and screening of an RNA optimized fluorinated fragment library

Fragment-based screening is an efficient method for early-stage drug discovery. In this study, we aimed to create a fragment library optimized for producing high hit rates against RNA targets. RNA has historically been an underexplored target, but recent research suggests potential for optimizing small molecule libraries for RNA binding. We extended this concept to fragment libraries to produce an RNA optimized fluorinated fragment library. We then screened this library, alongside two non-RNA optimized fragment libraries, against three RNA targets: the human cytoplasmic A-site and the S. cerevisiae tRNAAsp anticodon stem loop with and without nucleobase modifications. The screens yielded 24, 31, and 20 hits against the respective targets. Importantly, statistical analysis confirmed a significant overrepresentation of hits in our RNA optimized library. Based on these findings, we propose guidelines for developing RNA optimized fragment libraries. We hope the guidelines will help expediting fragment-based ligand discovery for RNA targets and contribute to presenting RNA as a promising target in drug discovery.

Comprehensive evaluation of antibacterial and anticancer activities from indole butanoic acid

Focus of this study is on the use of the hydrazone compound (3) (N-(4-bromobenzylidene)-4-(1H-indol-3-yl) butane hydrazide), which was previously prepared from the reaction of the compound p-bromobenzaldehyde with the corresponding hydrazide (2), as an intermediate compound for the synthesis of azetidine, thiazolidine, tetrazole, oxadiazole and phthalazine heterocyclic compounds through its reaction with some cyclic reagents and catalysts such as chloro acetyl chloride, thioglycolic acid, sodium-azid, lead dioxide and Hydrogen chloride gas. The prepared compounds were characterized using physical properties and also spectroscopic methods such as infrared spectroscopy, nuclear magnetic resonance spectra of the proton and the isotope of carbon13 as well as mass spectrometry, which accurately identified the proposed structures of the prepared compounds. The identity of the prepared compounds was determined using physical and spectroscopic properties, where infrared and 1HNMR spectroscopy of the proton as well as carbon13 were used in addition to using mass spectrometry to verify the validity of the prepared structures. Conclusions: Also, the biological antibacterial evaluation of the compounds (4-8) was conducted and it gave a good result compared to the drug (8) used as a reference for the control, The MTT test was performed on the healthy and cancerous cells of the compounds (4,5,8) and gave an excellent result for the compound (8).

Uncovering the role of fluorine positioning on the cationic properties of 2,4-difluoropyridine

Fluorine substitution exerts a profound influence on the electronic structures, ionization behaviours, and vibrational dynamics of pyridine systems, enabling the precise tuning of their molecular properties. 2,4-Difluoropyridine (2,4-DFP) exhibits a unique combination of inductive and resonance effects owing to the presence of fluorine atoms at the ortho and para positions relative to the nitrogen atom. However, studies on its ionization-induced structural changes and vibrational dynamics remain limited. In this study, high-resolution vacuum-ultraviolet mass-analysed threshold ionization mass spectroscopy and Franck-Condon analysis were employed to investigate the ionization-induced structural and electronic properties of 2,4-DFP. The spatial arrangement of fluorine atoms selectively stabilised the nitrogen lone pair and the π orbitals in the pyridine ring, significantly affecting valence orbital energies. Precise measurements of the adiabatic ionization energies of 2,4-DFP highlighted the synergistic effects of para-resonance and ortho-inductive withdrawal, thereby elucidating their roles in molecular stabilisation. Vibrational analyses of the proximate cationic states revealed mode-specific structural distortions, underscoring the dynamic changes induced by ionization. A comparative evaluation of 2,3-, 2,5-, and 2,6-DFP derivatives demonstrated how fluorine positioning governs ionization energies, molecular geometries, and vibronic interactions. This study advances the understanding of the chemistry of fluorinated pyridines and offers insights into their potential applications in the tailored molecular design of functional materials and chemical systems.

Photoinduced Late-Stage Radical Decarboxylative and Deoxygenative Coupling of Complex Carboxylic Acids and Their Derivatives

The simple and efficient conversion of carboxylic acids into structurally diverse organic molecules is highly desirable in chemical synthesis. This review covers recent developments in photocatalytic methodology for late-stage transformations of complex carboxylic acids and their derivatives enabled by radical decarboxylation and deoxygenation, highlighting some representative and significant contributions in this field. These advancements are categorized based on the reactivity patterns exhibited by the carboxylic acids. Several activation modes to generate alkyl or aryl radical intermediates during decarboxylation of carboxylic acids are presented, namely, single-electron transfer (SET) oxidation, ligand-to-metal charge transfer (LMCT), SET reduction, and energy transfer (EnT) processes. On the other hand, direct activation of C-O bonds in carboxylic acids mediated by phosphoranyl radicals has been discussed and illustrates their potential synthetic application for the synthesis of complex aldehydes, ketones and amides.

Enantioselective Synthesis of Chiral 1,4-Dihydroquinolines via Iridium-Catalyzed Asymmetric Partial Hydrogenation of Quinolines

Chiral 1,4-dihydroquinolines are frequently found in natural products and pharmaceuticals, yet a generally useful route for their synthesis remains elusive. Here, we present an asymmetric partial hydrogenation strategy to access enantioenriched 1,4-dihydroquinolines from quinolines. Our strategy involves incorporating an ester group at position 3 of the quinoline ring, thereby enhancing the electronic deficiency and polarity of the C3-C4 double bond. Employing a chiral Ir-SpiroPAP catalyst facilitated the hydrogenation of a wide variety of 4-substituted 3-ethoxycarbonylquinolines, yielding chiral 1,4-dihydroquinolines in high yields (up to 95%) with exceptional enantioselectivity and efficiency (up to 99% ee and 1840 TONs). Noteworthy for its scalability and practicality, the method provides a robust avenue for the synthesis of valuable compounds such as 9-aryl aza-podophyllotoxins and melatonin MT2 receptor modulators. Density functional theory calculations were performed to gain insights into the reaction mechanism and the origins of the enantioselectivity.

Metal-free four-component coupling of cyclic diarylchloronium salts, tetrahydrothiophene, amines and carbon dioxide

A four-component coupling reaction of cyclic diarylchloronium salts, tetrahydrothiophene, amines and CO2 has been reported for the first time under transition metal-free conditions, giving rise to a range of structurally diverse and useful sulfur-containing carbamates in high yields with excellent regioselectivities.

Design and Synthesis of Topoisomerases-Histone Deacetylase Dual Targeted Quinoline-Bridged Hydroxamates as Anticancer Agents

The multifactorial nature of cancer requires treatment that involves simultaneous targeting of associated overexpressed proteins and cell signaling pathways, possibly leading to synergistic effects. Herein, we present a systematic study that involves the simultaneous inhibition of human topoisomerases (hTopos) and histone deacetylases (HDACs) by multitargeted quinoline-bridged hydroxamic acid derivatives. These compounds were rationally designed considering pharmacophoric features and catalytic sites of the cross-talk proteins, synthesized, and assessed for their anticancer potential. Our findings revealed that the compound 5c significantly produced anticancer effects in vitro and in vivo by reducing the tumor growth and its size in the A549 cell-induced lung cancer xenograft model through multiple mechanisms, primarily by multi-inhibition of hTopoI/II and HDACs, especially HDAC1 via atypical binding. The present paper discusses detailed mechanistic biological investigations, structure-activity effects supported by computational docking studies, and DMPK studies and provides future scope for lead optimization and modification.

A review on pyrimidine-based pharmacophore as a template for the development of hybrid drugs with anticancer potential

The low efficacy and toxicity of traditional chemotherapy, led by drug resistance of targeted anticancer therapies, have mandated the exploration and development of anticancer molecules. In this league, hybrid drugs, owing to their peculiar multitargeted functionality and structural diversity, could serve as vital leads in this quest for drug discovery. They are plausibly found to offer added advantages considering the improved efficacy, low toxicity, and improved patient compliance. Among numerous heterocycles explored, pyrimidine derivatives epitomize as a valuable resource for the hybrid drug development due to their validated efficacy and versatility. The present review discusses the role of pyrimidine, a diversified pharmacophore in drug development and concepts of hybrid drugs. The study covers the recent advancements in pyrimidine-based hybrid pharmacophores. It delves further into the challenges in hybrid drug development and ongoing research in hybrid drug discovery. Furthermore, the challenges faced in developing hybrid molecules, such as their design and optimization complexities, bioavailability and pharmacokinetics issues, target identification and validation, and off-target effects, are discussed.

Dynamic Kinetic Resolution-Based Asymmetric Transfer Hydrogenation of Racemic 2-Substituted Quinolines

The synthesis of chiral tetrahydroquinolines (THQs) has garnered significant interest from medicinal chemists due to their frequent presence as pharmacophores in bioactive compounds. While existing synthetic methods have primarily focused on THQs with single or multiple endocyclic chiral centers, the selective construction of THQs with both endo- and exo-cyclic chiral centers remains a significant challenge that requires further development. This study introduces a dynamic kinetic resolution (DKR)-based transfer hydrogenation of racemic 2-substituted quinolines, which yields structurally novel chiral THQs with consecutive endo- and exo-cyclic chiral centers in excellent yields and stereoselectivities (59 examples, with generally >20:1 dr and >90% ee, up to three consecutive stereocenters). Our approach offers a mechanistically novel method for the asymmetric transformation of electron-deficient aromatic N-heterocycles and presents an innovative way to expand the chiral N-heterocycle chemical space for medicinal chemistry.

Photoredox-Catalyzed Three-Component Sulfonaminoalkynylation of Alkenes via a Radial/Polar Crossover

We report a photoredox-catalyzed three-component sulfonaminoalkynylation of alkenes with N-aminopyridine salts and potassium alkynyltrifluoroborate salts. This aminoalkylation reaction underwent a radial/polar crossover mechanism, which was distinguished from the previous reports. A variety of β-alkynylated sulfonamides were obtained in moderate to excellent yields. The versatility of this method was further evidenced by its successful application in modifying biological molecules in advanced stages of development.

Electrochemical Ring Opening and [3 + 2] Cycloaddition of Aziridines: Access to 1,2-Bifunctionalized Products and Imidazolines

Herein, we report an electricity-driven activation of aziridine via direct anodic oxidation to give N-heterocycles and 1,2-bifunctionalized products by excluding any oxidant/reductant or metal catalyst. Many structurally modified aziridines were employed in the presence of different nitriles. A large variety of nucleophiles were screened to furnish chemoselectively O-alkylated and C-alkylated products. Late-stage derivatization of aziridine with natural and medicinally active compounds has also been done. Remarkably, our strategy was found to be a greener, sustainable, and atom-economical approach (E-factor = ca. 0.8). Azetidine was also found to be compatible with our protocol and generated six-membered N-heterocycles. The detailed mechanistic study highlighted that the reaction is driven via the generation of an aziridine radical cation followed by the SN2 nucleophilic attack.

Cu-Catalyzed Diastereo- and Enantioselective Synthesis of Borylated Cyclopropanes with Three Contiguous Stereocenters

Direct synthesis of enantioenriched scaffolds with multiple adjacent stereocenters remains an important yet challenging task. Herein, we describe a highly diastereo- and enantioselective Cu-catalyzed alkylboration of cyclopropenes, with less reactive alkyl iodides as electrophiles, for the efficient synthesis of tetra-substituted borylated cyclopropanes bearing three consecutive stereocenters. This protocol features mild conditions, a broad substrate scope, and good functional group tolerance, affording an array of chiral borylated cyclopropanes in good to high yields with excellent diastereo- and enantioselectivities. Detailed mechanistic experiments and kinetic studies were conducted to elucidate the reaction pathway and the rate-determining step of the reaction. DFT calculations revealed that the π···π stacking interaction between the phenyl groups on the substrate and the phosphorus ligand, along with the smaller distortion in the CuL-Bpin part, contributed to the high diastereo- and enantioselectivities. The synthetic utility of the protocol was showcased by the facile synthesis of some valuable chiral cyclopropanes with multiple chiral centers.

Visible-Light-Induced Imine Hydrogenation Catalyzed by Thioxanthone-TfOH Complex

Amino compounds are important molecules, commonly found in nature and widely applied in industrial production. Recently, photocatalysis has been discovered as an efficient method to synthesize amino compounds by promoting imine hydrogenation. In this work, a strategy of imine hydrogenation catalyzed by 2e- consecutive photoinduced electron transfer (ConPET) process of thioxanthone-TfOH complex (9-HTXTF) was thoroughly investigated with its reaction conditions optimized, substrate scope examined, and reaction mechanism elucidated, which provides an efficient method for synthesizing amino compounds.

Visible Light-Induced Divergent Deoxygenation/Hydroxymethylation of Pyridine N-Oxides

This study explores the deoxygenation of pyridine N-oxides and presents a one-step photoredox method for the direct synthesis of 2-hydroxymethylated pyridines from pyridine N-oxides. Mechanism studies elucidate the role of the catalyst and provide evidence of the possible electron transfer process and the formation of key radicals. A range of pyridine derivatives, particularly 2-hydroxymethyl-substituted pyridines, which may be difficult to obtain, can be synthesized in a single step.