Achiral 2-pyridone and 4-aminopyridine act as chiral inducers of asymmetric autocatalysis with amplification of enantiomeric excess via the formation of chiral crystals

Enantiomorphous crystals of achiral 2-pyridone and 4-aminopyridine served as sources of chirality, to induce the asymmetric autocatalysis of 5-pyrimidyl alkanol during the asymmetric addition of diisopropylzinc to the corresponding pyrimidine-5-carbaldehyde, that is, the Soai reaction. Following a significant amplification of enantiomeric excess through asymmetric autocatalysis, highly enantioenriched 5-pyrimidyl alkanol could be synthesized with their corresponding absolute configurations to those of chiral crystals of 2-pyridone and 4-aminopyridine.

Proton-transfer salts of diphenylphosphinic acid with substituted 2-aminopyridine: crystal structure, spectroscopic and DFT studies

Three proton-transfer salts of diphenylphosphinic acid (DPPA) with 2-amino-5-(X)-pyridine (AMPY, X = Cl, CN or CH₃), namely, 2-amino-5-chloropyridinium diphenylphosphinate, C₅H₆ClN₂⁺·C₁₂H₁₀O₂P^- (1, X = Cl), 2-amino-5-cyanopyridinium diphenylphosphinate, C₆H₆N₃⁺·C₁₂H₁₀O₂P^- (2, X = CN), and 2-amino-5-methylpyridinium diphenylphosphinate, C₆H₉N₂⁺·C₁₂H₁₀O₂P^- (3, X = CH₃), have been synthesized and characterized by FT-IR and ¹H NMR spectroscopy, and X-ray crystallography. The crystal structures of compounds 1-3 were determined in the space group P\overline{1} for 1 and 2, and C2/c for 3. All three compounds contain N-H...O hydrogen-bonding interactions due to proton transfer from the O=P-OH group of DPPA as donor to the pyridine N atom of AMPY as acceptor. The proton transfer of compounds 1-3 was also verified by ¹H NMR and FT-IR spectroscopy. The stoichiometry of all three proton-transfer salts was determined to be 1:1 and the Benesi-Hildebrand equation was applied to determine the formation constant (K_CT) and the molar extinction coefficient (ϵ_CT) in each case. Theoretical density functional theory (DFT) calculations were performed to investigate the optimized geometries, the molecular electrostatic potentials (MEP) and the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of all three proton-transfer salts. The results showed good agreement between the experimental data and the DFT computational analysis.

Synthesis and Fluorescent Properties of Aminopyridines and the Application in "Click and Probing"

Unsubstituted pyridin-2-amine has a high quantum yield and is a potential scaffold for a fluorescent probe. However, the facile access to conjugated highly substituted aminopyridines and the study of their fluorescent properties is scarce. In this paper, synthesis and fluorescent properties of multisubstituted aminopyridines were studied based on a recently developed Rh-catalyzed coupling of vinyl azide with isonitrile to form a vinyl carbodiimide intermediate, following tandem cyclization with an alkyne. An aminopyridine substituted with an azide group as a potential probe was further designed, synthesized, and evaluated. The “clicking-and-probing” experiment of it on BSA protein showed the potential of aminopyridine as a scaffold of a biological probe.

Induction of Λ-helicity in a zinc complex with an alanine-appended aminopyridine ligand

The crystal structure of tris[dimethyl 5-({1-[(pyridin-2-yl-κN)carbamoyl-κO]ethyl}carbamoyl)benzene-1,3-dicarboxylate]zinc(II) dinitrate acetonitrile trisolvate, [Zn(C₁₉H₁₉N₃O₆)₃](NO₃)₂·3CH₃CN or [Zn(L)₃](NO₃)₂·3CH₃CN, (1), has been determined by single-crystal X-ray diffraction. The neutral ligand L coordinates to the Zn²⁺ cation in a bidentate fashion via the pyridine N atom and an amide O atom, forming a six-membered chelate ring. The Λ-helical chirality of the Zn²⁺ coordination sphere is induced by pendant L-alanine residues through stacking interactions between the arene groups of two coordinated ligands, assisted by a hydrogen bond between amide groups bonded to the stacked arene rings. The third ligand is coordinated to the Zn²⁺ cation by the same six-membered chelate ring, but in the opposite direction with respect to the analogous chelate rings of the first two coordinated ligands. Besides ionic interactions between [ZnL₃]²⁺ complexes and NO₃^- anions, several types of hydrogen bonds and intermolecular stacking interactions contribute to the stability of the solid-state phase.

Concentration-QT modelling of the novel DHFR inhibitor P218 in healthy male volunteers

Aims

Given the increasing emergence of drug resistance in Plasmodium, new antimalarials are urgently required. P218 is an aminopyridine that inhibits dihydrofolate reductase being developed as a malaria chemoprotective drug. Assessing the effect of new compounds on cardiac intervals is key during early drug development to determine their cardiac safety.

Methods

This double‐blind, randomized, placebo‐controlled, parallel group study evaluated the effect of P218 on electrocardiographic parameters following oral administration of seven single‐ascending doses up to 1000 mg in 56 healthy volunteers. Participants were randomized to treatment or placebo at a 3:1 ratio. P218 was administered in the fasted state with standardized lunch served 4 hours after dosing. 12‐lead ECGs were recorded in triplicate at regular intervals on the test day, and at 48, 72, 120, 168, 192 and 240 hours thereafter. Blood samples for pharmacokinetic evaluations were collected at similar time points. Concentration‐effect modelling was used to assess the effect of P218 and its metabolites on cardiac intervals.

Results

Concentration–effect analysis showed that P218 does not prolong the QTcF, J‐Tpeak or TpTe interval at all doses tested. No significant changes in QRS or PR intervals were observed. Two‐sided 90% confidence intervals of subinterval effects of P218 and its metabolites were consistently below the regulatory concern threshold for all doses. Study sensitivity was confirmed by significant shortening of QTcF after a meal.

Conclusion

Oral administration of P218 up to 1000 mg does not prolong QTcF and does not significantly change QRS or PR intervals, suggesting low risk for drug‐induced proarrhythmia.

Overcoming presynaptic effects of VAMP2 mutations with 4-aminopyridine treatment

Clinical and genetic features of five unrelated patients with de novo pathogenic variants in the synaptic vesicle-associated membrane protein 2 (VAMP2) reveal common features of global developmental delay, autistic tendencies, behavioral disturbances, and a higher propensity to develop epilepsy. For one patient, a cognitively impaired adolescent with a de novo stop-gain VAMP2 mutation, we tested a potential treatment strategy, enhancing neurotransmission by prolonging action potentials with the aminopyridine family of potassium channel blockers, 4-aminopyridine and 3,4-diaminopyridine, in vitro and in vivo. Synaptic vesicle recycling and neurotransmission were assayed in neurons expressing three VAMP2 variants by live-cell imaging and electrophysiology. In cellular models, two variants decrease both the rate of exocytosis and the number of synaptic vesicles released from the recycling pool, compared with wild-type. Aminopyridine treatment increases the rate and extent of exocytosis and total synaptic charge transfer and desynchronizes GABA release. The clinical response of the patient to 2 years of off-label aminopyridine treatment includes improved emotional and behavioral regulation by parental report, and objective improvement in standardized cognitive measures. Aminopyridine treatment may extend to patients with pathogenic variants in VAMP2 and other genes influencing presynaptic function or GABAergic tone, and tested in vitro before treatment.

Discovery of aminopyridine-containing spiro derivatives as EGFR mutations inhibitors

Neratinib is an oral pan HER inhibitor, that irreversibly inhibits EGFR and HER2 and was proven to be effective against multiple EGFR mutations. In previous study, we reported spiro [indoline-3, 4′-piperidine]-2-ones as anticancer agents. In this study, we designed aminopyridine-containing spiro [indoline-3,4′-piperidine] derivatives A1-A4 using Neratinib and spiro [indoline-3, 4′-piperidine]-2-one compound patented as lead structure, then replaced piperidine with cyclopropane to obtain B1-B7 and replaced indoline with benzmorpholine to get C1-C4 and D1-D2. We synthesized these compounds and evaluated their residual activities under 0.5 M drug concentration on EGFR and ERBB2. Most of compounds showed stronger inhibition on EGFR-wt and ERBB2, in which A1-A4 showed excellent inhibitory activity with inhibition percentage on EGFR-wt kinase of 7%, 6%, 19%, 27%, respectively and 9%, 5%, 12%, 34% on ERBB2 kinase compared with 2% and 6% of Neratinib.

An efficient new method for the synthesis of 3-[18 F]fluoro-4-aminopyridine via Yamada-Curtius rearrangement

4-Aminopyridine is a clinically approved drug to improve motor symptoms in multiple sclerosis. A fluorine-18-labeled derivative of this drug, 3-[¹⁸ F]fluoro-4-aminopyridine, is currently under investigation for positron emission tomography (PET) imaging of demyelination. Herein, the Yamada-Curtius reaction has been successfully applied for the preparation of this PET radioligand with a better radiochemical yield and improved specific activity. The overall radiochemical yield was 5 to 15% (n = 12, uncorrected) with a specific activity of 37 to 148 GBq/μmol (end of synthesis) in a 90 minute synthesis time. It is expected that this 1 pot Yamada-Curtius reaction can be used to prepare similar fluorine-18-labeled amino substituted heterocycles.

Selective Removal of the Genotoxic Compound 2-Aminopyridine in Water using Molecularly Imprinted Polymers Based on Magnetic Chitosan and β-Cyclodextrin

To develop efficient materials with enhanced adsorption and selectivity for genotoxic 2-aminopyridine in water, based on magnetic chitosan (CTs) and β-cyclodextrin (β-CD), the magnetic molecularly imprinted polymers (MMIPs) of Fe₃O₄-CTs@MIP and Fe₃O₄-MAH-β-CD@MIP were synthesized by a molecular imprinting technique using 2-aminopyridine as a template. The selective adsorption experiments for 2-aminopyridine were performed by four analogues including pyridine, aniline, 2-amino-5-chloropyridine and phenylenediamine. Results showed the target 2-aminopyridine could be selectively adsorbed and quickly separated by the synthesized MMIPs in the presence of the above structural analogues. The coexisting ions including Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻ and SO₄²⁻ showed little effect on the adsorption of 2-aminopyridine. The maximum adsorption capacity of 2-aminopyridine on Fe₃O₄-CTs@MIP and Fe₃O₄-MAH-β-CD@MIP was 39.2 mg·g⁻¹ and 46.5 mg·g⁻¹, respectively, which is much higher than values in previous reports. The comparison result with commercial activated carbon showed the obtained MMIPs had higher adsorption ability and selectivity for 2-aminopyridine. In addition, the synthesized MMIPs exhibited excellent performance of regeneration, which was used at least five times with little adsorption capacity loss. Therefore, the synthesized MMIPs are potential effective materials in applications for selective removal and analysis of the genotoxic compound aminopyridine from environmental water.

Aminopyridyl/Pyrazinyl Spiro[indoline-3,4'-piperidine]-2-ones As Highly Selective and Efficacious c-Met/ALK Inhibitors

A series of novel aminopyridyl/pyrazinyl-substituted spiro[indoline-3,4'-piperidine]-2-ones were designed, synthesized, and tested in various in vitro/in vivo pharmacological and antitumor assays. 6-[6-Amino-5-[(1R)-1-(2,6-dichloro-3-fluorophenyl)ethoxy]-3-pyridyl]-1'-methylspiro[indoline-3,4'-piperidine]-2-one (compound 5b or SMU-B) was identified as a potent, highly selective, well-tolerated, and orally efficacious c-Met/ALK dual inhibitor, which showed pharmacodynamics effect by inhibiting c-Met phosphorylation in vivo and significant tumor growth inhibitions (>50%) in GTL-16 human gastric carcinoma xenograft models.

New Promising Compounds with in Vitro Nanomolar Activity against Trypanosoma cruzi

The antiparasitic activity of azole and new 4-aminopyridine derivatives has been investigated. The imidazoles 1 and 3-5 showed a potent in vitro antichagasic activity with IC50 values in the low nanomolar concentration range. The (S)-1, (S)-3, and (S)-5 enantiomers showed (up to) a thousand-fold higher activity than the reference drug benznidazole and furthermore low cytotoxicity on rat myogenic L6 cells.

2-Deoxystreptamine Conjugates by Truncation-Derivatization of Neomycin

A small library of truncated neomycin-conjugates is prepared by consecutive removal of 2,6-diaminoglucose rings, oxidation-reductive amination of ribose, oxidation-conjugation of aminopyridine/aminoquinoline and finally dimerization. The dimeric conjugates were evaluated for antibacterial activity with a unique hemocyanin-based biosensor. Based on the outcome of these results, a second-generation set of monomeric conjugates was prepared and found to display significant antibacterial activity, in particular with respect to kanamycin-resistant E. coli.

A mild, catalyst-free synthesis of 2-aminopyridines

Alkylation of 2-mercaptopyridine with 1,2-dibromoethane affords a cyclic dihydrothiazolopyridinium salt that can serve as a precursor of 2-aminopyridines. Its reaction with primary or secondary amines, either neat or in DMSO, under mild conditions gives the title compounds.