Applications of fluorine-containing amino acids for drug design

Photoinduced Copper-Mediated Difluoroalkylation of Arylsulfonium Salts with XCF2COR

Photoredox fluoroalkylation has emerged as a powerful method and have unlocked new possibilities in organic chemistry. In this work, the green-light-induced copper-mediated difluoroalkylation of arylsulfonium salts with different XCF2COR reagents is described. The reaction proceeded smoothly at ambient temperature under mild conditions and allowed the formation of a variety of difluoroalkylated arenes in good yields. The photocatalyst, visible-light, and Cu(I) salt played a synergetic role in the reduction of arylsulfonium salt and XCF2COR to the respective radical intermediates. This metallophotoredox protocol was applicable to the late-stage difluoroalkylation of multifunctionalized bioactive molecules, offering opportunities to the discovery of new medicinal agents. The transformation showed advantages of mildness, simple operation, good functional group tolerance, a wide range of substrates, and excellent regioselectivity, which provided an interesting alternative to other difluoroalkylation reactions in terms of structural diversity, selectivity, and availability by the application of arylsulfonium platforms.

Inverse conjugate additions of acrylic amides and esters with F/Cl/O/N-nucleophiles and CF3+ reagents

The conjugate additions of nucleophiles to conjugate acceptors are among the most powerful hetero-carbon bond formation reactions. The conjugate addition normally occurs via a β-nucleophilic addition, resulting in the formation of a stabilized α-carbanion intermediate that can be subsequently quenched by electrophiles or protons. Nevertheless, the inverse conjugate addition involving an α-specific nucleophilic addition remains less explored because of the electronic mismatch. In this research, we disclosed an α-specific nucleophilic addition of the nucleophiles including Py·HF, TBACl, HOR, H2O, H218O, RCO2H, and pyrazole to conjugate acceptors concurrent with a trifluoromethylation. This umpolung and inversely regioselective conjugate addition, enabled by a visible light-induced redox photocatalysis, occurred via an unusual α-nucleophilic addition other than the normal β-nucleophilic addition to efficiently generate diverse α-functionalized CF3-containing amides/esters. The broad substrate scope, excellent functional-group tolerance, and versatile late-stage derivatizations as well as the biologically and functionally important CF3-containing products demonstrated the potential applications of this protocol in materials, agrochemicals, and pharmaceutical chemistry.

A facile synthesis of CF3-containing iminoisobenzofurans via copper-catalyzed oxygen trifluoromethylation-cyclization of o-vinyl-N-alkylamide

A copper-catalyzed oxygen trifluoromethylation of o-vinyl-N-alkylamide using Togni reagent as the trifluoromethyl precursor is demonstrated for the efficient synthesis of trifluoromethyl-containing iminoisobenzofurans. Preliminary mechanistic studies indicate that free radicals are involved in this process. The advantages of this approach include relatively mild reaction conditions and good functional group tolerance.

Regioselective intermolecular carboamination of allylamines via nucleopalladation: empowering three-component synthesis of vicinal diamines

An intermolecular carboamination reaction of allyl amines under Pd(ii)-catalysis is reported, expediting the synthesis of valuable vicinal diamines embedded in a functionally enriched linear carbon framework with high yields and exclusive Markovnikov selectivity. Central to our approach is the strategic use of a removable picolinamide auxiliary, which directs the regioselectivity during aminopalladation and stabilizes the crucial 5,5-palladacycle intermediate. This stabilization facilitates oxidative addition to carbon electrophiles, enabling the simultaneous incorporation of diverse aryl/styryl groups as well as important amine motifs, such as sulfoximines and anilines, across carbon-carbon double bonds. The protocol features broad substrate compatibility, tolerance to various functional groups, and scalability. The utility of this method is further demonstrated by the site-selective diversification of pharmaceutical agents. Additionally, these products serve as versatile intermediates for synthesizing heterocycles and function as effective ligands in catalytic transfer hydrogenation reactions. Notably, this work represents a rare instance of nucleopalladation-guided intermolecular carboamination of allylamines.

Recent advances in the synthesis of N-heterocycles from α-amino acids mediated by iodine

The synthesis of N-heterocycles has received extensive attention from scientists considering their important role in organic synthesis, pharmaceuticals, and materials chemistry. α-Amino acids (α-AAs), both natural and non-natural, are structurally diverse, containing basic amino groups, acidic carboxyl groups, and various side-chain R groups in a single molecule. Given their structural properties and wide range of sources, they have undoubtedly become suitable synthetic building blocks for organic synthesis. However, conventional transformations of amino acids (AAs) focus on the amino and carboxyl groups independently. Conversions for these two prominent functional groups generally do not affect both their alpha positions and their branched chains. Over the past decade, with the application of iodine (I2) in the field of heterocyclic synthesis, the use of α-AAs for diverse construction of complex N-heterocyclic structures has gained increasing attention. This synthetic strategy relies on the I2-mediated Strecker degradation, which introduces α-AAs as electrophilic carbon species into the domino reaction sequence via decarboxylation and deamination processes. In this review, we have summarized recent advances in this emerging area.

Construction of a Defective Chiral Covalent Organic Framework for Fluorescence Recognition of Amino Acids

The design and synthesis of chiral covalent organic frameworks (COFs) with controlled defect sites are highly desirable but still remain largely unexplored. Herein, we report the synthesis of a defective chiral HD-TAPB-DMTP COF by modifying the chiral monomer helicid (HD) into the framework of an achiral imine-linked TAPB-DMTP COF using a chiral monomer exchange strategy. Upon the introduction of the chiral HD unit, the obtained defective chiral HD-TAPB-DMTP COF not only displays excellent crystallinity, large specific surface area (up to 2338 m2/g) and rich accessible chiral functional sites but also exhibits fluorescence emission, rendering it a good candidate for discrimination of amino acids. Notably, the resultant defective chiral HD-TAPB-DMTP COF can be used as a fluorescent sensor for enantioselective recognition of both tyrosine and phenylalanine enantiomers in water, showing enhanced fluorescent responses for the L conformations over those of the D conformations with the enantioselectivity factors being 1.84 and 2.02, respectively. Moreover, molecular docking simulations uncover that stronger binding affinities between chiral HD-TAPB-DMTP COF and L-tyrosine/L-phenylalanine in comparison to those with D-tyrosine/D-phenylalanine play important roles in enantioselective determination. This work provides new insights into the design and construction of highly porous defective chiral COFs for enantioselective fluorescence recognition of amino acids.

Fluorinated Peptide Hydrogels Result in Longer In Vivo Residence Time after Subcutaneous Administration

Peptide-based hydrogels are of interest to biomedical applications. Herein, we have explored the introduction of fluorinated amino acids in hydrogelator H-FQFQFK-NH2 (P1) to design a series of fluorinated peptide hydrogels and evaluate the in vitro and in vivo properties of the most promising analogues. The impact of fluorinated groups on peptide gelation, secondary structure, and self-assembly processes was assessed. We show that fluorine can significantly improve hydrogel stiffness, compared to the nonfluorinated reference P1. For P15 (H-FQFQF(o-CF3)K-NH2), P18 (H-FQFQF(F5)K-NH2), and P19 (H-FQFQM(CF3)K-NH2), microscopy studies scrutinized fiber morphologies and alignment in the network. In vitro release studies of hydrogels loaded with an opioid cargo suggested improved hydrogel stability for P15 and P18. This improved stability was further validated in vivo, notably for P15, giving the most significant increased gel residence time, with more than 20% of hydrogel still present 9 days post-injection, as monitored by nuclear SPECT-CT imaging.

Recent Progress in the Electrochemical Formation of C-N Bonds for Construction of Organic Compounds via the Use of NOx/NOx. CHEMSUSCHEM 2024:e202401751. [PMID: 39375153 DOI: 10.1002/cssc.202401751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Emissions of nitrogen oxide (NOx) species (NO and NO2) and nitrate/nitrite NOx -, such as NO3 - and NO2 -, have led to serious water pollution and climate challenges. How to remove these wastes is a global problem that urgently needs to be addressed. As reported, electrochemical catalytic technology under ambient conditions is of great interest for NOx/NOx - removal. Additionally, the in situ utilization of surface-adsorbed nucleophilic intermediates generated from the electrochemical reduction of NOx/NOx - can provide a sustainable strategy for building C-N bonds, upgrading waste NOx/NOx - into value-added organic products, such as amines, oximes, amides, and amino acids, while remediating the environment. This review summarizes the most recent progress in the construction of nitrogen compounds by coupling electrochemical NOx/NOx - reduction reactions with inorganic/organic substrates, focuses on understanding the adsorption-transformation mechanism during the NOx/NOx - reduction process, and discusses multiple side reactions and complex pathways. Important strategies, such as coupled system development and catalyst preparation, are also presented to broaden the range of nitrogen compounds and improve yields. Finally, a few key challenges and future research directions for the development of efficient and low-cost electrochemical C-N coupling processes are discussed.

Incorporation of CF3-pseudoprolines into polyproline type II foldamers confers promising biophysical features

The development and the use of fluorinated polyproline-type II (PPII) foldamers are still underexplored. Herein, trifluoromethyl pseudoprolines have been incorporated into polyproline backbones without affecting their PPII helicity. The ability of the trifluoromethyl groups to increase hydrophobicity and to act as 19F NMR probes is demonstrated. Moreover, the enzymatic stability and the non-cytotoxicity of these fluorinated foldamers make them valuable templates for use in medicinal chemistry.

Ribosomal translation of fluorinated non-canonical amino acids for de novo biologically active fluorinated macrocyclic peptides

Fluorination has emerged as a promising strategy in medicinal chemistry to improve the pharmacological profiles of drug candidates. Similarly, incorporating fluorinated non-canonical amino acids into macrocyclic peptides expands chemical diversity and enhances their pharmacological properties, from improved metabolic stability to enhanced cell permeability and target interactions. However, only a limited number of fluorinated non-canonical amino acids, which are canonical amino acid analogs, have been incorporated into macrocyclic peptides by ribosomes for de novo construction and target-based screening of fluorinated macrocyclic peptides. In this study, we report the ribosomal translation of a series of distinct fluorinated non-canonical amino acids, including mono-to tri-fluorinated variants, as well as fluorinated l-amino acids, d-amino acids, β-amino acids, etc. This enabled the de novo discovery of fluorinated macrocyclic peptides with high affinity for EphA2, and particularly the identification of those exhibiting broad-spectrum activity against Gram-negative bacteria by targeting the BAM complex. This study not only expands the scope of ribosomally translatable fluorinated amino acids but also underscores the versatility of fluorinated macrocyclic peptides as potent therapeutic agents.

Visible-Light-Induced Difunctionalization of 3-Butenoic Acid with Bromodifluoromethyl Heteroarylsulfones

Herein, we report a visible-light-induced iridium-promoted direct bifunctionalization of 3-butenoic acid with bromodifluoromethyl heteroarylsulfones. This methodology enables the concurrent introduction of difluoromethyl heteroarylsulfone and bromine groups into 3-butenoic acid under mild reaction conditions. Various α-substituted 3-butenoic acids and bromodifluoromethyl heteroarylsulfones were found to be compatible, yielding the corresponding products in moderate to good yields. This method opens a new route for the synthesis of fluorocarboxylic acid derivatives.

Synthesis of N-Sulfinyl Sulfoximines from 5-(Sulfoximido)dibenzothiophenium Triflates and Sodium Sulfinates

A transition-metal-free and efficient S-O/S-N bond interconversion reaction has been developed. The protocol facilitates an efficient synthesis of N-sulfinyl sulfoximines by reacting sulfoximido-substituted sulfonium salts with a wide range of sodium sulfinates, featuring broad substrate scope, including a plethora of heterocyclic and fluoroalkyl substrates, high functional group tolerance, and mild conditions.

Diverse role, structural trends, and applications of fluorinated sulphonamide compounds in agrochemical and pharmaceutical fields

Our knowledge of fluorine's unique and complex properties has significantly increased over the past 20 years. Consequently, more sophisticated and innovative techniques have emerged to incorporate this feature into the design of potential drug candidates. In recent years, researchers have become interested in synthesizing fluoro-sulphonamide compounds to discover new chemical entities with distinct and unexpected physical, chemical, and biological characteristics. The fluorinated sulphonamide molecules have shown significant biomedical importance. Their potential is not limited to biomedical applications but also includes crop protection. The discovery of novel fluorine and Sulfur compounds has highlighted their importance in the chemical sector, particularly in the agrochemical and medicinal fields. Recently, several fluorinated sulphonamide derivatives have been developed and frequently used by agriculturalists to produce food for the growing global population. These molecules have also exhibited their potential in health by inhibiting various human diseases. In today's world, it is crucial to have a steady supply of innovative pharmaceutical and agrochemical molecules that are highly effective, less harmful to the environment, and affordable. This review summarizes the available information on the activity of Fluorine and Sulphonamide compounds, which have proven active in pharmaceuticals and agrochemicals with excellent environmental and human health approaches. Moreover, it focuses on the current literature on the chemical structures, the application of fluorinated sulphonamide compounds against various pathological conditions, and their effectiveness in crop protection.

Fluorinated Protein-Ligand Complexes: A Computational Perspective

Fluorine is an element renowned for its unique properties. Its powerful capability to modulate molecular properties makes it an attractive substituent for protein binding ligands; however, the rational design of fluorination can be challenging with effects on interactions and binding energies being difficult to predict. In this Perspective, we highlight how computational methods help us to understand the role of fluorine in protein-ligand binding with a focus on molecular simulation. We underline the importance of an accurate force field, present fluoride channels as a showcase for biomolecular interactions with fluorine, and discuss fluorine specific interactions like the ability to form hydrogen bonds and interactions with aryl groups. We put special emphasis on the disruption of water networks and entropic effects.

Visible-Light-Induced Hydrodifluoromethylation of Unactivated Alkenes with Difluoroacetic Anhydride

We herein described a practical and efficient protocol for hydrodifluoromethylation of unactivated alkenes using readily available difluoroacetic anhydride as a difluoromethyl source by merging photocatalysis and N-hydroxyphthalimide activation. This method features a wide substrate scope and excellent compatibility with various functional groups, as demonstrated by more than 50 examples, including bioactive molecules and pharmaceutical derivatives. Mechanism investigation indicated that N-hydroxyphthalimide may also serve as the hydrogen atom donor.

Microwave‐Assisted Synthesis of Fluorinated 5‐Membered Nitrogen Heterocycles

The fluorinated 5‐membered N‐containing heterocyclic compounds have wide utility in varied fields. The importance of these compounds has encouraged researchers to explore environment‐friendly synthetic techniques for their synthesis. In this context, microwave‐assisted synthesis has proved beneficial for the synthesis of fluorinated 5‐membered N‐heterocycles in an environmentally benign and energy‐efficient manner. Compared to conventional heating, it offers several advantages, including quick heating, short reaction times, higher yields, and fewer side reactions. This article highlights the microwave‐assisted fluorination of 5‐membered N‐heterocyclic compounds along with the synthesis of fluorinated 5‐membered N‐heterocyclic compounds using fluorinated starting materials.

Phosphine-Catalyzed Domino Annulation of γ-Vinyl Allenoates: Synthesis of Tetrahydrofuro[3,2-c]quinoline Derivatives

A novel phosphine-catalyzed domino annulation reaction of γ-vinyl allenoates and o-aminotrifluoacetophenones for the construction of terahydrofuro[3,2-c]quinoline derivatives has been developed. In this domino reaction, two kinds of terahydrofuro[3,2-c]quinoline compounds containing CF3 groups were obtained with good yields under mild conditions, three new C-N, C-C, and C-O bonds can be built in one step, and the reaction selectivity is achieved by adjusting the reaction conditions. Furthermore, preliminary studies on an asymmetric variant of this reaction proceeded with moderate enantioselectivity.

Composition and Conformation of Hetero- versus Homo-Fluorinated Triazolamers Influence their Activity on Islet Amyloid Polypeptide Aggregation

Novel fluorinated foldamers based on aminomethyl-1,4-triazolyl-difluoroacetic acid (1,4-Tz-CF2) units were synthesized and their conformational behaviour was studied by NMR and molecular dynamics. Their activity on the aggregation of the human islet amyloid polypeptide (hIAPP) amyloid protein was evaluated by fluorescence spectroscopy and mass spectrometry. The fluorine labelling of these foldamers allowed the analysis of their interaction with the target protein. We demonstrated that the preferred extended conformation of homotriazolamers of 1,4-Tz-CF2 unit increases the aggregation of hIAPP, while the hairpin-like conformation of more flexible heterotriazolamers containing two 1,4-Tz-CF2 units mixed with natural amino acids from the hIAPP sequence reduces it, and more efficiently than the parent natural peptide. The longer heterotriazolamers having three 1,4-Tz-CF2 units adopting more folded hairpin-like and ladder-like structures similar to short multi-stranded β-sheets have no effect. This work demonstrates that a good balance between the structuring and flexibility of these foldamers is necessary to allow efficient interaction with the target protein.

Selective Electrocatalytic Conversion of Nitric Oxide to High Value-Added Chemicals

The artificial disturbance in the nitrogen cycle has necessitated an urgent need for nitric oxide (NO) removal. Electrochemical technologies for NO conversion have gained increasing attention in recent years. This comprehensive review presents the recent advancements in selective electrocatalytic conversion of NO to high value-added chemicals, with specific emphasis on catalyst design, electrolyte composition, mass diffusion, and adsorption energies of key intermediate species. Furthermore, the review explores the synergistic electrochemical co-electrolysis of NO with specific carbon source molecules, enabling the synthesis of a range of valuable chemicals with C─N bonds. It also provides in-depth insights into the intricate reaction pathways and underlying mechanisms, offering valuable perspectives on the challenges and prospects of selective NO electrolysis. By advancing comprehension and fostering awareness of nitrogen cycle balance, this review contributes to the development of efficient and sustainable electrocatalytic systems for the selective synthesis of valuable chemicals from NO.

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.

Synthesis and biological evaluation of selective Pepstatin based trifluoromethylated inhibitors of Cathepsin D

Cathepsin D (CD) is overexpressed in several types of cancer and constitutes an important biological target. Pepstatin A, a pentapeptide incorporating two non-proteinogenic statin residues, is among the most potent inhibitor of CD but lacks selectivity and suffers from poor bioavailability. Eight analogues of Pepstatin A, were synthesized, replacing residues in P3 or P1 position by non-canonical (S)- and (R)-α-Trifluoromethyl Alanine (TfmAla), (S)- and (R)-Trifluoromethionine (TFM) or non-natural d-Valine. The biological activities of those analogues were quantified on isolated CD and Pepsin by fluorescence-based assay (FRET) and cytotoxicity of the best fluorinated inhibitors was evaluated on SKOV3 ovarian cancer cell line. (R)-TFM based analog of Pepstatin A (compound 6) returned a sub-nanomolar IC50 against CD and an increased selectivity. Molecular Docking experiments could partially rationalize these results. Stabilized inhibitor 6 in the catalytic pocket of CD showed strong hydrophobic interactions of the long and flexible TFM side chain with lipophilic residues of S1 and S3 sub-pockets of the catalytic pocket. The newly synthesized inhibitors returned no cytotoxicity at IC50 concentrations on SKOV3 cancer cells, however the compounds derived from (S)-TfmAla and (R)-TFM led to modifications of cells morphologies, associated with altered organization of F-actin and extracellular Fibronectin.

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

An efficient multicomponent reaction of newly designed β-trifluoromethyl β-diazo esters, acetonitrile, and carboxylic acids via an interrupted esterification process under copper-catalyzed conditions has been developed, which affords various unsymmetrical β-trifluoromethyl N,N-diacyl-β-amino esters in good to excellent yields. The reaction features mild conditions, a wide scope of β-amino esters and carboxylic acids, and also applicability to large-scale synthesis, thus providing an efficient way for the synthesis of β-trifluoromethyl β-diacylamino esters. Furthermore, this reaction represents the first example of a Mumm rearrangement of β-trifluoromethyl β-diazo esters.

Desymmetrization of Geminal Difluoromethylenes using a Palladium/Copper/Lithium Ternary System for the Stereodivergent Synthesis of Fluorinated Amino Acids

Fluorinated amino acids and related peptides/proteins have been found widespread applications in pharmaceutical and agricultural compounds. However, strategies for introducing a C-F bond into amino acids in an enantioselective manner are still limited and no such asymmetric catalysis strategy has been reported. Herein, we have successfully developed a Pd/Cu/Li ternary system for stereodivergent synthesis of chiral fluorinated amino acids. This method involves a sequential desymmetrization of geminal difluoromethylenes and allylic substitution with amino acid Schiff bases via Pd/Li and Pd/Cu dual activation, respectively. A series of non-natural amino acids bearing a chiral allylic/benzylic fluorine motif are easily synthesized in high yields with excellent regio-, diastereo-, and enantioselectivities (up to >20 : 1 dr and >99 % ee). A density functional theory (DFT) study revealed the F-Cu interaction of the allylic substrate and the Cu catalyst significantly influence the stereoselectivity.

Synthesis of α-Trifluoromethyl Alkynes through Fluoroalkynylation of gem-Difluoroalkenes

A trifluoromethylalkynylation reaction of gem-difluoroalkenes with alkynyl sulfoxide by photoredox radical addition with good functional group tolerance in moderate to high yields, is developed for the synthesis of α-trifluoromethyl alkyne. This reaction features simple operation and inexpensive raw materials and provides an expeditious route to synthesize biologically relevant fluorine-containing alkynyl compounds with diverse structural skeletons.

Obtaining Pure 1H NMR Spectra of Individual Pyranose and Furanose Anomers of Reducing Deoxyfluorinated Sugars

Due to tautomeric equilibria, NMR spectra of reducing sugars can be complex with many overlapping resonances. This hampers coupling constant determination, which is required for conformational analysis and configurational assignment of substituents. Given that mixtures of interconverting species are physically inseparable, easy-to-use techniques that enable facile full 1H NMR characterization of sugars are of interest. Here, we show that individual spectra of both pyranoside and furanoside forms of reducing fluorosugars can be obtained using 1D FESTA. We discuss the unique opportunities offered by FESTA over standard sel-TOCSY and show how it allows a more complete characterization. We illustrate the power of FESTA by presenting the first full NMR characterization of many fluorosugars, including of the important fluorosugar 2-deoxy-2-fluoroglucose. We discuss in detail all practical considerations for setting up FESTA experiments for fluorosugars, which can be extended to any mixture of fluorine-containing species interconverting slowly on the NMR frequency-time scale.

Trifluoromethylthiolation of Tryptophan and Tyrosine Derivatives: A Tool for Enhancing the Local Hydrophobicity of Peptides

The incorporation of fluorinated groups into peptides significantly affects their biophysical properties. We report herein the synthesis of Fmoc-protected trifluoromethylthiolated tyrosine (CF3S-Tyr) and tryptophan (CF3S-Trp) analogues on a gram scale (77-93% yield) and demonstrate their use as highly hydrophobic fluorinated building blocks for peptide chemistry. The developed methodology was successfully applied to the late-stage regioselective trifluoromethylthiolation of Trp residues in short peptides (66-80% yield) and the synthesis of various CF3S-analogues of biologically active monoamines. To prove the concept, Fmoc-(CF3S)Tyr and -Trp were incorporated into the endomorphin-1 chain (EM-1) and into model tripeptides by solid-phase peptide synthesis. A remarkable enhancement of the local hydrophobicity of the trifluoromethylthiolated peptides was quantified by the chromatographic hydrophobicity index determination method, demonstrating the high potential of CF3S-containing amino acids for the rational design of bioactive peptides.

Mechanism of molecular interaction of sitagliptin with human DPP4 enzyme - New Insights

PURPOSE

Dipeptidyl peptidase 4 (DPP4) inactivates a range of bioactive peptides. The cleavage of insulinotropic peptides and glucagon-like peptide 1 (GLP1) by DPP4 directly influences glucose homeostasis. This study aimed to describe the mode of interaction between sitagliptin (an antidiabetic drug) and human DPP4 using in silico approaches.

MATERIALS AND METHODS

Docking studies were conducted using AutoDock Vina, 2D and 3D schematic drawings were obtained using PoseView and PLIP servers, and the DPP4-sitagliptin complex was visualized with Pymol software.

RESULTS

The best affinity energy to form the DPP4-sitagliptin complex was E-value ​= ​- 8.1 ​kcal ​mol-1, as indicated by docking simulations. This result suggests a strong interaction. According to our observations, hydrophobic interactions involving the amino acids residues Tyr663 and Val712, hydrogen bonds (Glu203, Glu204, Tyr663, and Tyr667), π-Stacking interactions (Phe355 and Tyr667), and halogenic bonds (Arg123, Glu204, and Arg356) were prevalent in the DPP4-sitagliptin complex. Root Mean Square Deviation prediction also demonstrated that the global structure of the human DPP4 did not have a significant change in its topology, even after the formation of the DPP4-sitagliptin complex.

CONCLUSION

The stable interaction between the sitagliptin ligand and the DPP4 enzyme was demonstrated through molecular docking simulations. The findings presented in this work enhance the understanding of the physicochemical properties of the sitagliptin interaction site, supporting the design of more efficient gliptin-like iDPP4 inhibitors.

LiBF4-Promoted Aromatic Fluorodetriazenation under Mild Conditions

An efficient and mild fluorination method through LiBF4-promoted aromatic fluorodetriazenation of 3,3-dimethyl-1-aryltriazenes is developed. The reaction proceeds smoothly and tends to complete within 2 h in the absence of a protic acid or strong Lewis acid. This method tolerates a wide range of functional groups and affords the aryl fluoride products in moderate to excellent yields.

Tinker, Tailor, Soldier, Spy: The Diverse Roles That Fluorine Can Play within Amino Acid Side Chains

Side chain-fluorinated amino acids are useful tools in medicinal chemistry and protein science. In this review, we outline some general strategies for incorporating fluorine atom(s) into amino acid side chains and for elaborating such building blocks into more complex fluorinated peptides and proteins. We then describe the diverse benefits that fluorine can offer when located within amino acid side chains, including enabling 19F NMR and 18F PET imaging applications, enhancing pharmacokinetic properties, controlling molecular conformation, and optimizing target-binding.

Chemistry and Pharmacology of Fluorinated Drugs Approved by the FDA (2016-2022)

Fluorine is characterized by high electronegativity and small atomic size, which provide this molecule with the unique property of augmenting the potency, selectivity, metabolic stability, and pharmacokinetics of drugs. Fluorine (F) substitution has been extensively explored in drug research as a means of improving biological activity and enhancing chemical or metabolic stability. Selective F substitution onto a therapeutic or diagnostic drug candidate can enhance several pharmacokinetic and physicochemical properties such as metabolic stability and membrane permeation. The increased binding ability of fluorinated drug target proteins has also been reported in some cases. An emerging line of research on F substitution has been addressed by using 18F as a radiolabel tracer atom in the extremely sensitive methodology of positron emission tomography (PET) imaging. This review aims to report on the fluorinated drugs approved by the US Food and Drug Administration (FDA) from 2016 to 2022. It cites selected examples from a variety of therapeutic and diagnostic drugs. FDA-approved drugs in this period have a variety of heterocyclic cores, including pyrrole, pyrazole, imidazole, triazole, pyridine, pyridone, pyridazine, pyrazine, pyrimidine, triazine, purine, indole, benzimidazole, isoquinoline, and quinoline appended with either F-18 or F-19. Some fluorinated oligonucleotides were also authorized by the FDA between 2019 and 2022.

New Approved Drugs Appearing in the Pharmaceutical Market in 2022 Featuring Fragments of Tailor-Made Amino Acids and Fluorine

The strategic fluorination of oxidatively vulnerable sites in bioactive compounds is a relatively recent, widely used approach allowing us to modulate the stability, bio-absorption, and overall efficiency of pharmaceutical drugs. On the other hand, natural and tailor-made amino acids are traditionally used as basic scaffolds for the development of bioactive molecules. The main goal of this review article is to emphasize these general trends featured in recently approved pharmaceutical drugs.

Merging Copper(I) Photoredox Catalysis and Iodine(III) Chemistry for the Oxy-monofluoromethylation of Alkenes

A simple process for the oxy-monofluoromethylation of alkenes is described. In combination with visible-light copper(I) photoredox catalysis, an easily accessible iodine(III) reagent containing monofluoroacetoxy ligands serves as a powerful source of a monofluoromethyl (CH₂ F) radical, enabling the step economical synthesis of γ-fluoro-acetates from a broad range of olefinic substrates under mild conditions. Applications to late-stage diversification of alkenes derived from complex molecules, amino acids and the synthesis of fluoromethylated heterocycles are also demonstrated.

Palladium-Catalyzed [6+2] Double Allene Annulation for Benzazocines Synthesis

An efficient double allene protocol for the formation of benzazocines has been developed. The reaction constitutes a highly regioselective palladium-catalyzed formal [6+2] annulation of allenyl benzoxazinanones with terminal allenes forming the challenging 8-membered cycles. Decent yields and excellent regioselectivity have been observed under mild conditions with a remarkable Z-stereoselectivity for the exo-cyclic C=C bonds. The synthetic potentials of benzazocine products have been demonstrated.

Synthesis, molecular docking, and antioxidant activity of new fluorescent tetrafluoroterphenyl analogues

Nucleophilic aromatic substitution (S_N Ar) chemistry has been applied to develop many functionalized pentafluorobenzene derivatives. Those compounds are highly specific at the para position of the fluorinated ring. Therefore, they are typical adducts for the preparation of antioxidant molecular systems. In this context, we report the use of S_N Ar chemistry as a suitable and simple approach for the synthesis of fluorescent antioxidant perfluorinated materials bearing ether bonds in various para-substituted alkoxy chains and with high purity and excellent yields. The fluoroterphenyl core was prepared via alkylation, Cu(I)-assisted decarboxylation, and cross-coupling using the potassium salt of fluorobenzoate, followed by the reaction with different alcohols. The structures of the synthesized fluoroterphenyl adducts were investigated using FT-IR, ¹ H NMR, ¹³ C NMR, and ¹⁹ F NMR spectroscopy. The emission spectra and absorption spectra showed solvatochromism. The newly prepared tetrafluoroterphenyl analogues were investigated by antioxidant examination using the 2,2-diphenyl-1-picrylhydrazyl assay. Results were compared with ascorbic acid and butylated hydroxytoluene as references, and revealed that the tetrafluoroterphenyl analogues containing a decyl chain had the highest activity, with an IC₅₀ value of 22.36 ± 0.19 g/ml. The produced tetrafluoroterphenyl analogues were used in molecular docking strategies with a Protein Data Bank protein ID 5IKQ. The antioxidant investigations and docking results were convergent.

Fast, highly enantioselective, and sustainable fluorination of 4-substituted pyrazolones catalyzed by amide-based phase-transfer catalysts

Highly enantioselective and sustainable fluorination of 4-substituted pyrazolones has been developed by amide-based phase-transfer catalysts.

Cobalt-electrocatalytic C-H hydroxyalkylation of N-heteroarenes with trifluoromethyl ketones

Trifluoromethyl carbinols and N-heteroarenes are both prevalent in bioactive molecules. However, access to high-value pharmacophores combining these two functional groups still remains a challenge. Herein, we report an electro-chemical redox-neutral coupling for the synthesis of N-heteroaryl trifluoromethyl carbinols from readily available N-heteroarenes and trifluoromethyl ketones. The reaction starts with reversing the polarity of ketones to nucleophilic ketyl radicals through an electrocatalytic proton-coupled electron transfer (PCET), followed by radical addition to heteroarenes and rearomatization to afford tertiary alcohol products. Importantly, the merging of paired electrolysis and cobalt catalysis is crucial to this regioselective C-H hydroxyalkylation of heteroarenes, and thus avoids several known competing pathways including the spin-center shift (SCS) process. Collectively, this protocol provides straightforward access to heteroaryl trifluoromethyl carbinols, featuring ideal atom economy, excellent regioselectivity, and paired redox-neutral electrolysis.

Electronic and structural study of T315I mutated form in DFG-out conformation of BCR-ABL inhibitors

In this work, the four main drugs for the treatment of chronic myeloid leukemia were analyzed, being imatinib, dasatinib, nilotinib and ponatinib followed by four derivative molecules of nilotinib and ponatinib. For these derivative molecules, the fluorine atoms were replaced by hydrogen and chlorine atoms in order to shade light to the structural effects on this set of inhibitors. Electronic studies were performed at density functional theory level with the B3LYP functional and 6-311+G(d,p) basis set. The frontier molecular orbitals, gap HOMO-LUMO, and NBO were analyzed and compared to docking studies for mutant T315I tyrosine kinase protein structure code 3IK3, in the DFG-out conformation. Structural similarities were pointed out, such as the presence of groups common to all inhibitors and modifications raised up on new generations of imatinib-based inhibitors. One of them is the trifluoromethyl group present in nilotinib and later included in ponatinib, in addition to the 1-methylpiperazin-1-ium group that is present in imatinib and ponatinib. The frontier molecular orbitals of imatinib and ponatinib are contributing to the same amino acid residues, and the ineffectiveness of imatinib against the T315I mutation was discussed.Communicated by Ramaswamy H. Sarma.

Water Network in the Binding Pocket of Fluorinated BPTI-Trypsin Complexes─Insights from Simulation and Experiment

Structural waters in the S1 binding pocket of β-trypsin are critical for the stabilization of the complex of β-trypsin with its inhibitor bovine pancreatic trypsin inhibitor (BPTI). The inhibitor strength of BPTI can be modulated by replacing the critical lysine residue at the P1 position by non-natural amino acids. We study BPTI variants in which the critical Lys15 in BPTI has been replaced by α-aminobutyric acid (Abu) and its fluorinated derivatives monofluoroethylglycine (MfeGly), difluoroethylglycine (DfeGly), and trifluoroethylglycine (TfeGly). We investigate the hypothesis that additional water molecules in the binding pocket can form specific noncovalent interactions with the fluorinated side chains and thereby act as an extension of the inhibitors. We report potentials of mean force (PMF) of the unbinding process for all four complexes and enzyme activity inhibition assays. Additionally, we report the protein crystal structure of the Lys15MfeGly-BPTI-β-trypsin complex (pdb: 7PH1). Both experimental and computational data show a stepwise increase in inhibitor strength with increasing fluorination of the Abu side chain. The PMF additionally shows a minimum for the encounter complex and an intermediate state just before the bound state. In the bound state, the computational analysis of the structure and dynamics of the water molecules in the S1 pocket shows a highly dynamic network of water molecules that does not indicate a rigidification or stabilizing trend in regard to energetic properties that could explain the increase in inhibitor strength. The analysis of the energy and the entropy of the water molecules in the S1 binding pocket using grid inhomogeneous solvation theory confirms this result. Overall, fluorination systematically changes the binding affinity, but the effect cannot be explained by a persistent water network in the binding pocket. Other effects, such as the hydrophobicity of fluorinated amino acids and the stability of the encounter complex as well as the additional minimum in the potential of mean force in the bound state, likely influence the affinity more directly.

Application of a fluorine strategy in the lead optimization of betulinic acid to the discovery of potent CD73 inhibitors

The ecto-5'-nucleotidase (CD73) is an important enzyme in the adenosine pathway and catalyzes the extracellular hydrolysis of adenosine monophosphate (AMP) yielding adenosine which is involved in the inflammation and immunosuppression. Inhibitors of CD73 have potential as novel immunotherapy agents for the treatment of cancer and infection. In this study, we discovered a series of fluorinated betulinic acid derivatives as potent CD73 inhibitors by a fluorine scanning strategy. Among these, three compounds ZM522, ZM553 and ZM557 exhibited inhibitory activity with IC₅₀ values of 0.56 uM, 0.74 uM and 0.47 uM, respectively. In addition, these compounds showed a 7-fold, 5-fold and 8-fold increase in activity compared to the positive control drug α, β-methylene adenosine diphosphate (APCP) against the human CD73 enzyme. Two of these (ZM522 and ZM553) also exhibited effective interferon gamma (INF-γ) elevation and indicated the regulation of rescued T cell activation. Therefore, our study provides both a lead optimization strategy and potential compounds for further development of small molecule CD73 inhibitors.

Microwave-assisted Synthesis of Fluorinated Heterocycles

Abstract:

The diverse biological applications of fluorinated heterocycles make them crucial chemical compounds. Several synthetic processes have been developed for their synthesis. Microwave-assisted synthesis has emerged as an important technique for generating fluorinated heterocycles in an eco-friendly and energy-efficient manner. It provides several benefits like less reaction time, high reaction yield, homogeneous heat distribution leading to lower side reaction, and better control of reaction temperature. Recently there has been significant progress in microwave use for heterocycle synthesis. This article discusses the applications of microwave irradiation in the synthesis of oxygen- and nitrogen-containing fluorinated heterocycles.

Direct C(sp3)-H Polyfluoroarylation: Access to Polyfluoroaryl Amino Acids via Rh-Catalyzed Selective C-F Bond Cleavage

A catalytic selective C-F bond alkylation method for polyfluoroarene with glycinates and derivatives in the presence of a DavePhos-ligated Rh catalyst was developed. This method avoids the preactivation of alkylating reagents and provides an efficient and straightforward route to synthesize a series of polyfluoroaryl amino acids via C(sp³)-H functionalization. This reaction proceeds under mild conditions and exhibits high reactivity and excellent chemoselectivities. Meanwhile, the synthetic potential of this method was demonstrated by gram-scale synthesis, and further transformations proved the application value of the products as well.

The Latest FDA-Approved Pharmaceuticals Containing Fragments of Tailor-Made Amino Acids and Fluorine

Nowadays, the selective introduction of fluorine into bioactive compounds is a mature strategy in the design of drugs allowing to increase efficiency, biological half-life and bio-absorption. On the other hand, amino acids (AAs) represent one of the most ubiquitious classes of naturally occurring organic compounds, which are found in over 40% of newly marked small-molecule pharmaceutical drugs and medical formulations. The primary goal of this work is to underscore two major trends in the design of modern pharmaceuticals. The first is dealing with the unique structural characteristics provided by the structure of amino acids featuring an abundance of functionality and the presence of a stereogenic center, all of which bodes well for the successful development of targeted bioactivity. The second is related to fine-tuning the desired activity and pharmacokinetics by selective introduction of fluorine. Historically, both trends were developed separately as innovative and prolific approaches in modern drug design. However, in recent decades, these approaches are clearly converging leading to an ever-increasing number of newly approved pharmaceuticals containing both structural features of amino acids and fluorine.

The current state of amyloidosis therapeutics and the potential role of fluorine in their treatment

Amyloidosis, commonly known as amyloid-associated diseases, is characterized by improperly folded proteins accumulating in tissues and eventually causing organ damage, which is linked to several disorders ranging from neurodegenerative to peripheral diseases. It has an enormous societal and financial impact on the global health sector. Due to the complexity of protein misfolding and intertwined aggregation, there are no effective disease-modifying medications at present, and the condition is likely mis/non-diagnosed half of the time. Nonetheless, over the last two decades, substantial research into aggregation processes has revealed the possibilities of new intervention approaches. On the other hand, fluorine has been a rising star in therapeutic development for numerous neurodegenerative illnesses and other peripheral diseases. In this study, we revised and emphasized the possible significance of fluorine-modified therapeutic molecules and fluorine-modified nanoparticles (NPs) in the modulation of amyloidogenic proteins, including insulin, amyloid beta peptide (Aβ), prion protein (PrP), transthyretin (TTR) and Huntingtin (htt).

Difluoromethylation of Unactivated Alkenes Using Freon-22 through Tertiary Amine-Borane-Triggered Halogen Atom Transfer

The application of abundant and inexpensive fluorine feedstock sources to synthesize fluorinated compounds is an appealing yet underexplored strategy. Here, we report a photocatalytic radical hydrodifluoromethylation of unactivated alkenes with an inexpensive industrial chemical, chlorodifluoromethane (ClCF₂H, Freon-22). This protocol is realized by merging tertiary amine-ligated boryl radical-induced halogen atom transfer (XAT) with organophotoredox catalysis under blue light irradiation. A broad scope of readily accessible alkenes featuring a variety of functional groups and drug and natural product moieties could be selectively difluoromethylated with good efficiency in a metal-free manner. Combined experimental and computational studies suggest that the key XAT process of ClCF₂H is both thermodynamically and kinetically favored over the hydrogen atom transfer pathway owing to the formation of a strong boron-chlorine (B-Cl) bond and the low-lying antibonding orbital of the carbon-chlorine (C-Cl) bond.

Mechanochemical Synthesis of Fluorinated Imines

A number of imines, including 12 new compounds, previously not reported in the literature, derived from variously fluorinated benzaldehydes and different anilines or chiral benzylamines were synthesized by a solvent-free mechanochemical method, which was based on the manual grinding of equimolar amounts of the substrates at the room temperature. In a very short reaction time of only 15 min, the method produced the expected products with good-to-excellent yields. The yields were comparable or significantly higher than those reported in the literature for the imines synthesized by other methods. Importantly, the conditions used for the reactions with aniline derivatives also resulted in the high yields of imines obtained from chiral benzylamines, and can be extended to the synthesis with other similar amines. Structures of all imines were confirmed by NMR spectroscopy: ¹H, ¹³C and ¹⁹F. For four compounds, X-ray structures were also obtained. The synthetic approach presented in this paper contributes to the prevention of environmental pollution and can be easily extended for larger-scale syntheses. The mechanochemical solvent-free method provides a convenient strategy particularly useful for the preparation of fluorinated imines being versatile intermediates or starting material in the synthesis of drugs and other fine chemicals.

Controllable Single and Double Difluoromethylene Insertions into C-Cu Bonds: Copper-Mediated Tetrafluoroethylation and Hexafluoropropylation of Aryl Iodides with TMSCF2H and TMSCF2Br

The selective difluoromethylene insertion into a C-Cu bond is a challenging task and is currently limited to either a single CF₂ insertion into CuCF₃ or double CF₂ insertions into CuC₆F₅ (or (Z)-CF₃CF = CFCu). Achieving both selective single and double CF₂ insertions into the same C-Cu bond is even more difficult. Herein, highly controllable single and double CF₂ insertions into CuCF₂H species with a TMSCF₂Br reagent have been described, affording two previously unknown fluoroalkylcopper species "Cu(CF₂)_nCF₂H" (n = 1 and 2) independently under different reaction conditions. This work represents the first example of both single and double CF₂ insertions into the same C-Cu bond in a highly selective manner. The synthetic value of the obtained "Cu(CF₂)_nCF₂H" (n = 1 and 2) species is demonstrated by their reactions with aryl iodides, halogenation agents, and cinnamyl chloride, which enables the direct transfer of HCF₂CF₂ and HCF₂CF₂CF₂ moieties into organic molecules. The key to controllable fluorocarbon chain elongation from C₁ to C₂ and from C₁ to C₃ is presumably attributed to the different reactivities of "Cu(CF₂)_nCF₂H" species (n = 0, 1, 2 and 3) and the loading of the TMSCF₂Br reagent.