Highlights on U.S. FDA-approved fluorinated drugs over the past five years (2018-2022)

Development of potent inhibitors targeting bacterial prolyl-tRNA synthetase through fluorine scanning-directed activity tuning

As essential enzymes encoded by single genes, aminoacyl-tRNA synthetases (aaRSs) have long been considered promising drug targets for combating microbial infections. In this study, we developed a novel class of amino acid-ATP dual-site inhibitors of prolyl-tRNA synthetase (ProRS) through the structural simplification of the intermediate product prolyl adenylate and its non-hydrolyzable mimic. The co-crystal structures of the compound PAA-5 bound to both Pseudomonas aeruginosa and human cytoplasmic ProRSs (PaProRS and HsPrors) were solved to high resolution. Utilizing the structural information gained, a fluorine scanning (F-scanning) strategy was applied to PAA-5, and the biochemical and biophysical assays demonstrated that fluorine substitutions at specific positions of PAA-5 selectively enhanced its activity against bacterial ProRS. The dual-fluorinated derivative PAA-38 exhibited the highest antibacterial potency, with a Kd value of 0.399 ± 0.074 nM and an IC50 value of 4.97 ± 0.98 nM against PaProRS and an MIC value of 4-8 μg mL-1 against tested bacterial strains. Our study provides a novel lead compound for the development of aaRS-based antibiotics and highlights F-scanning as a powerful strategy for lead optimization, particularly in pinpointing the subtle fluorophilic environments within the protein pocket to achieve better activity and selectivity.

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.

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.

Regio- and Diastereoselective Cascade Reactions of Bicyclo[1.1.0]butanes: Access to gem-Difluorinated Carbocyclic Rings

gem-Difluorinated carbocyclic rings are attractive motifs in drug development. Herein, we report the transition-metal free cascade reaction of bicyclo[1.1.0]butanes (BCBs) with gem-difluorocyclopropenes for the synthesis of gem-difluorinated carbocyclic rings with excellent regio- and diastereoselectivity. This method was successfully applied to provide a broad range of gem-difluorinated cyclopentenes and cyclopropanes, which could undergo a variety of difluoromethylene (CF2) retaining transformations.

Quantitative Generation of HF from KF and Formation of Amine-3HF Complexes by Using Cation Exchange Reaction Between KF and Amberlyst 15DRY

A safe and convenient method for the quantitative generation of hydrogen fluoride (HF) from potassium fluoride (KF) at room temperature was successfully demonstrated using the cation exchange reaction between KF and Amberlyst 15DRY in acetonitrile (MeCN). After one of the cation exchange reactions, HF was generated from KF in 69% yield. On the other hand, HF was generated quantitatively by removing the generated HF and repeating the cation exchange reaction seven times. During and after the cation exchange reaction, the generated HF was separated from the Amberlyst 15DRY by decantation and filtration without loss of HF. When the Amberlyst 15DRY was regenerated and then reused in the cation exchange reaction ten times, HF was generated almost quantitatively each time and the yield of HF did not decrease at all. In addition, when 1/3 equivalent of amines was added to the resulting HF-containing solution, a variety of amine-3HF complexes with controlled stoichiometric ratios were formed in quantitative yields.

5-Fluorouracil Impairs Transmission of Acetylcholine in the Hippocampus and Induces Cognitive Impairments in Mice

BACKGROUND

Chemotherapy-induced cognitive impairments are a significant adverse sequela of cancer treatment. The potential mechanism of chemotherapy-induced cognitive impairments remains elusive. The present study evaluated the impact of a commonly utilized chemotherapy agent, 5-fluorouracil (5-FU), on acetylcholine (ACh) levels in the hippocampus.

METHODS

5-FU was injected into mice once a day for 10 days to create a mouse model of chemotherapy-induced cognitive impairment. Microdialysis and HPLC-MS/MS were used to determine hippocampal ACh levels. Biocytin injection and patch-clamp recordings were performed on cholinergic (ChAT) neurons in the medial septum (MS) to observe their morphological and electrophysiological changes. Chemogenetic tools were used to activate ChAT neurons in the MS. The acetylcholinesterase inhibitor donepezil was injected i.p. into mice to elevate ACh levels in the brain.

RESULTS

Cognitive performance in mice was impaired after 5-FU treatment, accompanied by reduced ACh release in the hippocampus. The administration of 5-FU led to compromised structural integrity and diminished activity of ChAT neurons in the MS. Chemogenetic stimulation of MS ChAT neurons ameliorated the cognitive impairments. The administration of donepezil also reduced the cognitive impairments caused by 5-FU.

CONCLUSIONS

5-FU therapy caused cognitive impairments in mice by affecting the neuronal structure and activity of ChAT neurons in the MS. Inducing the increase of ACh levels could be a promising therapeutic approach for addressing 5-FU treatment-induced cognitive impairments.

Photo-induced decarboxylative radical cascade cyclization of unactivated alkenes: access to CF- and CF2-substituted ring-fused imidazoles

A mild and effective visible-light-induced decarboxylative radical cascade reaction of olefin-containing imidazoles with α-fluorinated carboxylic acids as building blocks containing CF or ArCF2 moieties, has been developed to afford a series of monofluoromethylated or aryldifluoromethylated polycyclic imidazoles in medium to excellent yields with features of simple operation, available raw materials, and wide substrate scopes. In addition, the mechanistic experiments indicated that the methodology involved a radical pathway.

Highlights on U.S. FDA-approved halogen-containing drugs in 2024

This comprehensive review offers an update on the FDA-approved halogen-containing drugs in 2024. The agency approved a total of 50 drugs, including small molecules and macromolecules. Excitingly, 16 out of 50 are halogen-containing drugs, indicated to diagnose, mitigate and treat the various human diseases. Among halogens, fluorine and chlorine are highly prevalent in drug discovery and development. Therefore, the properties of fluorine and chlorine and their impact on the drug profile are briefly discussed. In addition, the specific role of halogens in these drugs has been discussed with the help of structure-activity relationships (SARs), co-crystal structures, and closely related literature precedents. This review also provides the additional information for each drug, such as trade name, active ingredients, route of administration, approval date, sponsors, indication, mode of action, major drug metabolizing enzyme(s), and route of elimination. We expect that the present review may garner the attention of drug discovery researchers and inspire them toward the potential applications of halogens to discover novel therapeutics in the future.

A novel pyridine-2-one AMPK inhibitor: Discovery, mechanism, and in vivo evaluation in a hypoxic pulmonary arterial hypertension rat model

AMP-activated protein kinase (AMPK), a heterotrimeric serine-threonine kinase, has been identified as a promising target for regulating vascular remodeling in pulmonary arterial hypertension (PAH) due to its capacity to promote proliferation, autophagy, and anti-apoptosis in pulmonary artery smooth muscle cells (PASMCs). However, research into AMPK inhibitors is very limited. Herein, a virtual screening strategy was employed to identify CHEMBL3780091 as a lead compound for a series of novel AMPK inhibitors by exploring the structure-activity relationship around a specific pyridine-2-one scaffold. Subsequently, the most promising 13a was observed to exhibit excellent AMPK inhibitory activity and favorable anti-proliferative activity against PASMCs through the inhibition of the AMPK signaling pathway in vitro. Moreover, compound 13a significantly reduced right ventricular systolic pressure, attenuated vascular remodeling, and improved right heart function in hypoxia-induced PAH rats in vivo. In conclusion, this study provides a novel and potential lead compound for the study of AMPK inhibitors and a new direction for the development of PAH drugs that focus on improving vascular remodeling.

Selective Decarboxylative Fluorination of β-Keto Acids in Aqueous Media: 19F-NMR-Assisted Batch Optimization and Transfer to Continuous Flow

The selective decarboxylative fluorination of 3-oxo-3-phenylpropionic acid is used as a benchmark reaction to optimize it under biocompatible conditions in batch and to transfer it to continuous flow mode. The reaction conditions are varied with respect to temperature, fluorinating reagents, inorganic base additives, and pH, as these parameters have been identified as having a significant impact on the process. The formation of the products and any by-products is analyzed using gas chromatography (GC) and 19F nuclear magnetic resonance spectroscopy (NMR). Once optimal conditions have been determined, the reaction is carried out using an automated continuous laboratory synthesis system that features a mesostructured capillary reactor and an integrated 19F-NMR spectrometer for real-time monitoring of the reaction. The work presented here represents the initial phase of a multi-step continuous flow process that will include additional biocatalyzed downstream reactions in future applications.

Design, synthesis and investigation of biological activity and mechanism of fluoroaryl-substituted derivatives at the FL118 position 7

Addition of fluorine atoms into chemical compounds is a validated strategy to enhance their physical, chemical and biological properties. In this study, FL118, a novel camptothecin-related small molecule known for its unique mechanism of action and superior antitumor efficacy, was utilized as a foundational drug platform. By replacing the hydrogen atom at position 7 of FL118 with a fluoroaryl group, a diverse array of FL118 derivatives were synthesized. Our investigations revealed that the majority of these newly synthesized compounds exhibited improved cytotoxicity compared to FL118, with some demonstrating enhanced in vivo antitumor efficacy. Among these derivatives, compound 7h stood out and was subjected to detailed analysis. Compound 7h demonstrated a remarkable ability to inhibit colorectal cancer (CRC) cell colony formation and cell migration, while also promoting reactive oxygen species (ROS) production and CRC cell apoptosis. Notably, our studies unveiled that the presence of DDX5 could modulate Topoisomerase I (Top1) activity, a process effectively reversed by a low concentration of 7h, but not SN38. Moreover, only 7h was able to decrease DDX5 expression, SN38 was not. Molecular docking studies further supported the binding of 7h to DDX5. Interestingly, although both 7h and SN38 exhibited similar inhibitory effects on Top1 activity, only 7h, and not SN38, could inhibit DDX5. These findings not only pave the way for deeper mechanistic explorations of FL118 and its derivatives in cancer research but also position the identified compound 7h as a promising candidate for further development.

Electrochemical Fluorination of Organic Compounds Using a Hexafluorosilicate Salt as an Inexpensive and Widely Available Fluorine Source

The introduction of fluorine into organic molecules is of the utmost importance in the preparation of active pharmaceutical ingredients (APIs). While a wide range of fluorine sources for organic synthesis have been used over the past decades, the associated safety risks, cost, or environmental impact are still serious limitations. Hexafluorosilicate salts are one of the most inexpensive and readily available sources of nucleophilic fluorine, but they have so far not been used in organic synthesis. Herein we report the first example of the use of a hexafluorosilicate salt as a reagent for the formation of C-F bonds. We have selected as the model reaction an electrochemical decarboxylative fluorination procedure. The synthesis of bis(5-ethyl-2-methylpyridin-1-ium) hexafluorosilicate(IV) was key to obtaining a soluble and reactive hexafluorosilicate salt. This protocol enabled the synthesis of a wide range of primary, secondary, and tertiary aliphatic fluorides (22 examples) in up to 85% yield. The electrochemical method was also successfully transferred to a flow electrolysis cell, demonstrating its robustness and scalability. Finally, we extended the scope of the fluorine source by demonstrating its applicability to electrochemical benzylic C-H fluorination.

Synthesis of fluorine-containing bicyclo[4.1.1]octenes via photocatalyzed defluorinative (4 + 3) annulation of bicyclo[1.1.0]butanes with gem-difluoroalkenes

Although bicyclo[4.1.1] systems are privileged scaffolds in many natural products and drug molecules, efficient synthetic approaches to these systems remain underdeveloped. In this work, we disclose a photoredox-catalyzed defluorinative (4 + 3) annulation of bicyclo[1.1.0]butanes with gem-difluoroalkenes, which provides practical and straightforward access to the fluorine-containing bicyclo[4.1.1]octenes. Our protocol is characterized by mild conditions, broad substrate scope, excellent functional group tolerance and good to excellent yields. Notably, the ease and variety of product derivatizations further enrich the diversity and complexity of the fluorine-containing bicyclo[4.1.1] systems.

Visible-Light Photoredox-Catalyzed Radical-Polar Crossover 1,4-Hydrofluoromethylation of 1,3-Enynes

We report herein a visible-light photoredox-catalyzed 1,4-hydrofluoromethylation of terminal-alkene-derived 1,3-enynes with sodium fluoromethylsulfinate, providing an effective protocol to access a diversity of di- and trisubstituted allenes under mild conditions. The synthetic utility of the present protocol was demonstrated by a large-scale reaction as well as the synthetic derivatization of the allene product.

Fluorinated Sulfonamides: Synthesis, Characterization, In Silico, Molecular Docking, ADME, DFT Predictions, and Structure-Activity Relationships, as Well as Assessments of Antimicrobial and Antioxidant Activities

The design and synthesis of unique two series of fluorinated sulfonamides 3a-f and 5a-g utilizing nucleophilic aromatic substitution reactions of tetrafluorophthalonitrile 1 with various sulfonamides 2 under a variety of different reactions conditions were the key goals of the current research. The chemical composition of the generated products has been investigated via mass spectroscopy, 1HNMR, 13CNMR, infrared, and elemental analyzes. Antimicrobial studies were conducted in vitro to evaluate the activity of all new synthesized compounds against resistant strains. The first series showed high potency in very low concentrations. All compounds were studied against DPPH Radical Scavenging Activity and the other series showed high activity even in low molar ratio. In silico molecular docking was used to investigate the potential binding pathways for different receptors: dihydroprotien synthase protein (ID Code: 1AJ0) as an antibacterial and EGFRWT co-crystallized with erlotinib [PDB ID code 1m17]. Furthermore, synthesized compounds with good ADME predictions to the Lipinski rule of five demonstrated that the recently synthesized compounds had high drug-likeness qualities when the physicochemical parameter for the most powerful novel candidates was determined. Moreover, the DFT/B3LYP method functionalized with a 6-31G (d, p) basis set was employed to calculate quantum parameters, MEP analysis, HUMO, and LUMO.

Identification of novel brain penetrant GSK-3β inhibitors toward Alzheimer's disease therapy by virtual screening, molecular docking, dynamic simulation, and MMPBSA analysis

One of the significant therapeutic targets for Alzheimer's disease (AD) is Glycogen Synthase Kinase-3β (GSK-3β). Inhibition of GSK-3β can prevent hyperphosphorylation of tau, and thus prevent formation and accumulation of neurofibrillary tangles and neuropil threads that block intracellular transport, trigger unfolded protein response, and increase oxidative stress, cumulatively leading to neurodegeneration. In this study, we have performed structure-based virtual screening of two small-molecule libraries from ChemDiv CNS databases using AutoDock Vina to identify hit molecules based on their binding affinities compared to that of an established GSK-3β inhibitor, indirubin-3'-monoxime (IMO). Pharmacoinformatic screening on SwissADME and pkCSM servers enabled identification of lead molecules with favorable pharmacoinformatic properties for drug likeliness, including blood brain barrier (BBB) permeability. Further, molecular dynamic simulations identified six candidate lead molecules that show stable complex formation with GSK-3β in dynamic state under physiological conditions. Principal component analysis of the dynamic state was used to plot Free Energy Landscapes (FELs) of GSK-3β-ligand complexes. STRIDE secondary structure analysis of the lowest energy conformations identified from FEL plots, and binding free energy calculations by Molecular Mechanics Poisson-Boltzmann Surface Area ((ΔGbind)MM-PBSA) of the simulation trajectories led to the identification of two ligands as potential lead molecules having favorable free energy landscape profiles as well as significantly lower (ΔGbind)MM-PBSA in dynamic state compared to that of reference inhibitor IMO. Hence, this study identifies two novel brain penetrant GSK-3β inhibitors that are likely to have therapeutic potential against Alzheimer's disease.

The significance of chirality in contemporary drug discovery-a mini review

More than half of drugs are chiral compounds with their chirality determining their molecular interactions, ecofriendly environmental safety and efficacy. Overall nearly 90% of chiral compounds are marketed as racemates consisting of an equimolar mixture of two enantiomers. Despite having identical chemical structure and bonding, racemates function differently when exposed to chiral environments and demonstrate notable variances in biological properties such as pharmacology, toxicology, metabolism and pharmacokinetics, etc. Advancements in asymmetric synthesis in recent years have led to considerable interest in the development of single enantiomers of chiral drug molecules for medicinal chemistry settings. In this review, we want to compile examples of chiral medicines approved by the FDA in the years 2022 and 2023 with an emphasis on their synthesis along with information on chiral induction as well as enantiomeric excess.

Synthesis of Diverse N-Trifluoromethyl Pyrazoles by Trapping of Transiently-Generated Trifluoromethylhydrazine

A one-pot synthesis of functionalized N-trifluoromethyl pyrazoles from readily available di-Boc trifluoromethylhydrazine and dialdehydes, diketones, carbonylnitriles, and ketoesters/amides/acids is described. 19F NMR studies were used to characterize the stability of trifluoromethylhydrazine HCl salt in solution and in solid form and identified a short solution-state half-life of ∼6 h. Optimization of cyclization conditions identified DCM, combined with a strong acid, as a key to suppress the undesired des-CF3 side products, which formed as a result of the instability of trifluoromethylhydrazine and related intermediates. Despite the short-lived nature of these transient intermediates, their reactivity could be utilized to directly deliver a diverse array of pharmaceutically relevant N-trifluoromethyl pyrazoles in synthetically useful yields.

A Metal-Free Direct Decarboxylative Fluoroacylation of Indole Carboxylic Acids with Fluorinated Acids

A straightforward preparation of diversified fluorinated indol-3-yl ketones was developed by the direct decarboxylative fluoroacylation of indole carboxylic acids. The reaction could be performed on a gram scale under net conditions. Neither a metal catalyst nor an additive was employed. This methodology featured simple reaction conditions, high efficiency, exclusive selectivity, a broad substrate scope, and easy operation, which allowed it to meet the green chemistry requirement of the modern pharmaceutical industry. Control experiments confirmed that a radical process might be involved in the tandem decarboxylative fluoroacylation sequence.

Synthesis of Axially Chiral Monofluoroalkenes via Nickel-Catalyzed Reductive Cross-Coupling of gem-Difluoroalkenes

Enantioenriched monofluoroalkenes are important structural motifs in life science and functional materials. To date, only limited strategies were reported for the synthesis of monofluoroalkenes with stereogenic carbon centers; the axially chiral counterpart is still highly desirable. Herein, we report Ni-catalyzed defluorinative cross-electrophile coupling of gem-difluoroalkenes with biaryl electrophiles for the synthesis of axially chiral monofluoroalkenes. The resulting axially chiral monofluoroalkenes are formed with excellent regio- and stereoselectivities. Synthetic transformation of these axially enantioenriched monofluoroalkenes was also demonstrated.

Dithiocarbamate-based novel anti-histaminic agents: synthesis, characterization, crystal structure and thermal study

A new N-(4-fluorobenzyl) N-(pyridin-2-ylmethyl) dithiocarbamate ligand (fbpm) having structural similarity to clinically approved antihistaminic drugs (viz. pheniramine, chlorpheniramine, and brompheniramine) and its four metal complexes [Co(fbpm)3] (1), [Ni(fbpm)2] (2), [Cu(fbpm)2] (3), and [Zn(fbpm)2] (4) were successfully synthesized and characterized by various techniques i.e. elemental analysis, FT-IR spectroscopy, HR-MS, NMR spectroscopy, and absorption and emission spectroscopy. Furthermore, complexes 1 and 2 were characterized by single crystal X-ray diffraction. Complex 1 adopts distorted octahedral geometry around the Co(III) center while complex 2 adopts distorted square planar geometry around the Zn(II) center. X-ray data also showed various weak intermolecular C-H⋯F and C-H⋯N hydrogen bonding interactions leading to supramolecular architectures in complexes 1 and 2. The thermal decomposition study of complexes 1-4 analyzed by TGA shows that they are thermally stable up to 150 °C and also gives strong evidence for the formation of respective metal sulfides at higher temperatures. The antihistaminic activity of the ligand (fbpm) and its complexes 1-4 was examined against clonidine and haloperidol-induced catalepsy in Swiss albino mice of either gender in an in vivo animal model. The result shows that these synthesized compounds have antihistaminic potential to inhibit clonidine-induced catalepsy and may be targeted for different allergic conditions. Complex 3 showed maximum reduction in clonidine-induced catalepsy after 180 minutes of treatment when compared with the induced control.

Chloroimidazolium Deoxyfluorination Reagent with H2F3- Anion as a Sole Fluoride Source

In the study, we introduce an air-stable NHC-based deoxyfluorination reagent ImCl[H2F3], offering a promising avenue for deoxyfluorination across various substrates. Reagent efficiently fluorinates benzyl alcohols, carboxylic acids, and P(V) compounds without external fluoride sources. A mechanistic study reveals a two-step process involving benzyl chloride as an intermediate, shedding light on the two-step reaction pathway. The Hammet plot provides insights into reaction mechanisms with different substrates, enhancing our understanding of this versatile deoxyfluorination method.

The role of the methoxy group in approved drugs

The methoxy substituent is prevalent in natural products and, consequently, is present in many natural product-derived drugs. It has also been installed in modern drug molecules with no remnant of natural product features because medicinal chemists have been taking advantage of the benefits that this small functional group can bestow on ligand-target binding, physicochemical properties, and ADME parameters. Herein, over 230 methoxy-containing small-molecule drugs, as well as several fluoromethoxy-containing drugs, are presented from the vantage point of the methoxy group. Biochemical mechanisms of action, medicinal chemistry SAR studies, and numerous X-ray cocrystal structures are analyzed to identify the precise role of the methoxy group for many of the drugs and drug classes. Although the methoxy substituent can be considered as the hybridization of a hydroxy and a methyl group, the combination of these functionalities often results in unique effects that can amount to more than the sum of the individual parts.

Visible Light-Induced Radical Cascade Difluoromethylation/Cyclization of Unactivated Alkenes: Access to CF2H-Substituted Polycyclic Imidazoles

An efficient and mild protocol for the visible light-induced radical cascade difluoromethylation/cyclization of imidazoles with unactivated alkenes using easily accessible and bench-stable difluoromethyltriphenylphosphonium bromide as the precursor of the -CF2H group has been developed to afford CF2H-substituted polycyclic imidazoles in moderate to good yields. This strategy, along with the construction of Csp3-CF2H/C-C bonds, is distinguished by mild conditions, no requirement of additives, simple operation, and wide substrate scope. In addition, the mechanistic experiments have indicated that the difluoromethyl radical pathway is essential for the methodology.

Synthesis of Sterically Hindered Dialkyl Ethers via Palladium-Catalyzed Fluoro-alkoxylation of gem-Difluoroalkenes

Organofluorine compounds are of high value in medicinal and agricultural chemistry. Herein, we report a palladium-catalyzed fluoro-alkoxylation of gem-difluoroalkenes for the synthesis of much more challenging sterically hindered ethers. This reaction represents a direct synthesis method for α-trifluoromethyl ethers with a broad functional group tolerance and excellent regioselectivity. This system employs N-fluorobenzenesulfonimide (NFSI) as an electrophilic fluorine source and alcohols as nucleophilic donors, including but not limited to sterically hindered tert-substituted alcohols.

Discovery of 3-((4-Benzylpyridin-2-yl)amino)benzamides as Potent GPR52 G Protein-Biased Agonists

Orphan GPR52 is emerging as a promising neurotherapeutic target. Optimization of previously reported lead 4a employing an iterative drug design strategy led to the identification of a series of unique GPR52 agonists, such as 10a (PW0677), 15b (PW0729), and 24f (PW0866), with improved potency and efficacy. Intriguingly, compounds 10a and 24f showed greater bias for G protein/cAMP signaling and induced significantly less in vitro desensitization than parent compound 4a, indicating that reducing GPR52 β-arrestin activity with biased agonism results in sustained GPR52 activation. Further exploration of compounds 15b and 24f indicated improved potency and efficacy, and excellent target selectivity, but limited brain exposure warranting further optimization. These balanced and biased GPR52 agonists provide important pharmacological tools to study GPR52 activation, signaling bias, and therapeutic potential for neuropsychiatric and neurological diseases.

Liquid Chromatographic Enantioseparation of Newly Synthesized Fluorinated Tryptophan Analogs Applying Macrocyclic Glycopeptides-Based Chiral Stationary Phases Utilizing Core-Shell Particles

Due to the favorable features obtained through the incorporation of fluorine atom(s), fluorinated drugs are a group with emerging pharmaceutical importance. As their commercial availability is still very limited, to expand the range of possible candidates, new fluorinated tryptophan analogs were synthesized. Control of enantiopurity during the synthesis procedure requires that highly efficient enantioseparation methods be available. In this work, the enantioseparation of seven fluorinated tryptophans and tryptophan was studied and compared systematically to (i) develop analytical methods for enantioselective separations and (ii) explore the chromatographic features of the fluorotrytophans. For enantioresolution, macrocyclic glycopeptide-based selectors linked to core-shell particles were utilized, applying liquid chromatography-based methods. Application of the polar-ionic mode resulted in asymmetric and broadened peaks, while reversed-phase conditions, together with mobile-phase additives, resulted in baseline separation for all studied fluorinated tryptophans. The marked differences observed between the methanol and acetonitrile-containing eluent systems can be explained by the different solvation abilities of the bulk solvents of the applied mobile phases. Among the studied chiral selectors, teicoplanin and teicoplanin aglycone were found to work effectively. Under optimized conditions, baseline separations were achieved within 6 min. Ionic interactions were semi-quantitatively characterized and found to not influence enantiorecognition. Interestingly, fluorination of the analytes does not lead to marked changes in the chromatographic characteristics of the methanol-containing eluents, while larger differences were noticed when the polar but aprotic acetonitrile was applied. Experiments conducted on the influence of the separation temperature indicated that the separations are enthalpically driven, with only one exception. Enantiomeric elution order was found to be constant on both teicoplanin and teicoplanin aglycone-based chiral stationary phases (L < D) under all applied chromatographic conditions.

Orphan GPR52 as an emerging neurotherapeutic target

GPR52 is a highly conserved, brain-enriched, Gs/olf-coupled orphan G protein-coupled receptor (GPCR) that controls various cyclic AMP (cAMP)-dependent physiological and pathological processes. Stimulation of GPR52 activity might be beneficial for the treatment of schizophrenia, psychiatric disorders and other human neurological diseases, whereas inhibition of its activity might provide a potential therapeutic approach for Huntington's disease. Excitingly, HTL0048149 (HTL'149), an orally available GPR52 agonist, has been advanced into phase I human clinical trials for the treatment of schizophrenia. In this concise review, we summarize the current understanding of GPR52 receptor distribution as well as its structure and functions, highlighting the recent advances in drug discovery efforts towards small-molecule GPR52 ligands. The opportunities and challenges presented by targeting GPR52 for novel therapeutics are also briefly discussed.

Molecular dynamics and NMR reveal the coexistence of H-bond-assisted and through-space JFH coupling in fluorinated amino alcohols

The JFH coupling constants in fluorinated amino alcohols were investigated through experimental and theoretical approaches. The experimental JFH couplings were only reproduced theoretically when explicit solvation through molecular dynamics (MD) simulations was conducted in DMSO as the solvent. The combination of MD conformation sampling and DFT NMR spin-spin coupling calculations for these compounds reveals the simultaneous presence of through-space (TS) and hydrogen bond (H-bond) assisted JFH coupling between fluorine and hydrogen of the NH group. Furthermore, MD simulations indicate that the hydrogen in the amino group participates in both an intermolecular bifurcated H-bond with DMSO and in transmitting the observed JFH coupling. The contribution of TS to the JFH coupling is due to the spatial proximity of the fluorine and the NH group, aided by a combination of the non-bonding transmission pathway and the hydrogen bonding pathway. The experimental JFH coupling observed for the molecules studied should be represented as 4TS/1hJFH coupling.

4-Fluoro-benzyl (Z)-2-(2-oxoindolin-3-yl-idene)hydrazine-1-carbodi-thio-ate

The title compound, C16H12FN3OS, a fluorinated di-thio-carbazate imine derivative, was synthesized by the one-pot, multi-component condensation reaction of hydrazine hydrate, carbon di-sulfide, 4-fluoro-benzyl chloride and isatin. The compound demonstrates near-planarity across much of the mol-ecule in the solid state and a Z configuration for the azomethine C=N bond. The Z form is further stabilized by the presence of an intra-molecular N-H⋯O hydrogen bond. In the extended structure, mol-ecules are linked into dimers by N-H⋯O hydrogen bonds and further connected into chains along either [20] or [100] by weak C-H⋯S and C-H⋯F hydrogen bonds, which further link into corrugated sheets and in combination form the overall three-dimensional network.

The Role of Small Molecules Containing Fluorine Atoms in Medicine and Imaging Applications

The fluorine atom possesses many intrinsic properties that can be beneficial when incorporated into small molecules. These properties include the atom's size, electronegativity, and ability to block metabolic oxidation sites. Substituents that feature fluorine and fluorine-containing groups are currently prevalent in drugs that lower cholesterol, relieve asthma, and treat anxiety disorders, as well as improve the chemical properties of various medications and imaging agents. The dye scaffolds (fluorescein/rhodamine, coumarin, BODIPY, carbocyanine, and squaraine dyes) reported will address the incorporation of the fluorine atom in the scaffold and the contribution it provides to its application as an imaging agent. It is also important to recognize radiolabeled fluorine atoms used for PET imaging in the early detection of diseases. This review will discuss the many benefits of incorporating fluorine atoms into small molecules and give examples of fluorinated molecules used in the pharmaceutical industry and imaging techniques.

Trifluoromethyl-β-dicarbonyls as Versatile Synthons in Synthesis of Heterocycles

Trifluoromethyl group relishes a privileged position in the realm of medicinal chemistry because its incorporation into organic molecules often enhances the bioactivity by altering pharmacological profile of molecule. Trifluoromethyl-β-dicarbonyls have emerged as pivotal building blocks in synthetic organic chemistry due to their facile accessibility, stability and remarkable versatility. Owing to presence of nucleophilic and electrophilic sites, they offer multifunctional sites for the reaction. This review covers a meticulous exploration of their multifaceted role, encompassing an in-depth analysis of mechanism, extensive scope, limitations and wide-ranging applications in diverse organic synthesis, covering the literature from the 21st century. This comprehensive review encapsulates the applications of trifluoromethyl-β-dicarbonyls and their synthetic equivalents as precursors of complex and diverse heterocyclic scaffolds, fused heterocycles and spirocyclic compounds having medicinal and material importance. Their potent synthetic utility in cyclocondensation reactions with binucleophiles, cycloaddition reactions, C-C bond formations, asymmetric multicomponent reactions using classical/solvent-free/catalytic synthesis have been presented. Influence of unsymmetrical trifluoromethyl-β-diketones on regioselectivity of transformation is also reviewed. This review will benefit the synthetic and pharmaceutical communities to explore trifluoromethyl-β-dicarbonyls as trifluoromethyl building blocks for fabrication of heterocyclic scaffolds having implementation into drug discovery programs in the imminent future.

Silver-Enabled Dearomative Trifluoromethoxylation of Indoles

The only known method for the dearomative trifluoromethoxylation of indoles is preliminary, with only one substrate successfully undergoing the reaction. In this study, we not only developed a broadly applicable method for indole dearomative trifluoromethoxylation but also achieved divergent trifluoromethoxylation by fine-tuning the reaction conditions. Under optimized conditions, with a silver salt and an easily handled OCF3 reagent, various indoles smoothly underwent dearomatization to afford a diverse array of ditrifluoromethoxylated indolines in 50-84% isolated yields with up to 37:1 diastereoselectivity, and fluorinated trifluoromethoxylated indolines were obtained with exclusive trans selectivity. In addition, the reaction conditions were compatible with other heteroaromatic rings as well as styrene moieties.

Highlights on Fluorine-containing Drugs Approved by U.S. FDA in 2023

Fluorine continues to show its potential applications in drug discovery and development, as reflected by twelve drugs being fluorinated out of the fifty-five approved by the FDA in 2023. This concise review highlights the discovery of each of these fluorine-containing drugs in the past year, including its brand name, date of approval, composition, sponsors, indication, and mechanism of action. The relevant future trend is also briefly discussed.

Synthesis and Preclinical Evaluation of 22-[18F]Fluorodocosahexaenoic Acid as a Positron Emission Tomography Probe for Monitoring Brain Docosahexaenoic Acid Uptake Kinetics

Docosahexaenoic acid [22:6(n-3), DHA], a polyunsaturated fatty acid, has an important role in regulating neuronal functions and in normal brain development. Dysregulated brain DHA uptake and metabolism are found in individuals carrying the APOE4 allele, which increases the genetic risk for Alzheimer's disease (AD), and are implicated in the progression of several neurodegenerative disorders. However, there are limited tools to assess brain DHA kinetics in vivo that can be translated to humans. Here, we report the synthesis of an ω-radiofluorinated PET probe of DHA, 22-[18F]fluorodocosahexaenoic acid (22-[18F]FDHA), for imaging the uptake of DHA into the brain. Using the nonradiolabeled 22-FDHA, we confirmed that fluorination of DHA at the ω-position does not significantly alter the anti-inflammatory effect of DHA in microglial cells. Through dynamic PET-MR studies using mice, we observed the accumulation of 22-[18F]FDHA in the brain over time and estimated DHA's incorporation coefficient (K*) using an image-derived input function. Finally, DHA brain K* was validated using intravenous administration of 15 mg/kg arecoline, a natural product known to increase the DHA K* in rodents. 22-[18F]FDHA is a promising PET probe that can reveal altered lipid metabolism in APOE4 carriers, AD, and other neurologic disorders. This new probe, once translated into humans, would enable noninvasive and longitudinal studies of brain DHA dynamics by guiding both pharmacological and nonpharmacological interventions for neurodegenerative diseases.

Design, Synthesis, and Pharmacological Evaluation of Isoindoline Analogues as New HPK1 Inhibitors

Hematopoietic progenitor kinase 1 (HPK1) is an important negative regulator in T-cell receptor signaling and as a promising key target for immunotherapy. Herein, based on the reported HPK1 inhibitor 2 featuring an isofuranone component, a structural optimization approach was conducted leading to several series of derivatives characterized by containing an isoindoline structural motif. Compound 49 was identified as a new potent HPK1 inhibitor with an IC50 value of 0.9 nM, more potent than compound 2 (5.5 nM). It also has an improved IV profile in rats and enhanced aqueous solubility. It effectively inhibited pSLP76 and reinvigorated T-cell receptor (TCR) signaling, promoting T-cell function and cytokine production both in naïve and antigen-specific T cells. Furthermore, compound 49 reversed the inhibition on T-cell activity mediated by classic immunosuppressive factors in the tumor microenvironment (TME). In the murine CT-26 tumor model, this compound reinvigorated the T cell and synergistically enhanced the antitumor efficacy of anti-PD1 at a well-tolerant dosage.

Advances in Continuous Flow Fluorination Reactions

Fluorination reactions are important in constructing organofluorine motifs, which contribute to favorable biological properties in pharmaceuticals and agrochemicals. However, fluorination reagents and reactions are associated with various problems, such as their hazardous nature, high exothermicity, and poor selectivity and scalability. Continuous flow has emerged as a transformative technology to provide many advantages relative to batch syntheses. This review article summarizes recent continuous flow techniques that address the limitations and challenges of fluorination reactions. Approaches based on different flow techniques are discussed, including gas-liquid reactions, packed-bed reactors, in-line purifications, streamlined multistep synthesis, large-scale reactions well as flow photoredox- and electrocatalysis.

Amphiphilic small molecule antimicrobials: From cationic antimicrobial peptides (CAMPs) to mechanism-related, structurally-diverse antimicrobials

Bacterial infections are characterized by their rapid and widespread proliferation, leading to significant morbidity. Despite the availability of a variety of antimicrobial drugs, the resistance exhibited by pathogenic microorganisms towards these drugs demonstrates a consistent upward trajectory year after year. This trend can be attributed to the abuse or misuse of antibiotics. Although antimicrobial peptides can avoid the emergence of drug resistance to a certain extent, their clinical application has been hindered by factors such as their high production cost, poor in vivo stability, and potential cytotoxicity. Consequently, there arises an urgent need for the development of novel antimicrobial drugs. Small-molecule amphiphatic antimicrobials have a good prospect for research and development. These peptides hold the potential to address several issues, including the high cost of antimicrobial peptide production, poor in vivo stability, and cytotoxicity. Moreover, they exhibit the capability to overcome bacterial resistance, thereby considerably satisfying market demands and clinical needs. This paper reviews recent research pertaining to small molecule host-defending amphiphatic antimicrobials with cationic amphiphilic structures. It focuses on the design concepts, inherent relationships, drug-like properties, antimicrobial activities, application prospects, and emerging screening methods for novel antimicrobial. This review assumes paramount importance in mitigating the current shortcomings of antimicrobial agents. It also provides potential new ideas and methodologies for the research and development of antimicrobial agents.