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The year 2024 marked the 80th anniversary of Woodward’s total synthesis of quinine. Quinine is a natural alkaloid from the bark of the cinchona tree that has been used for years as an antimalarial drug. The antibacterial effect of quinine salts has also been regarded. With this in mind, a series of original 9-deoxycinchone alkaloid derivatives bearing a dialkylamino- or heterocyclic moiety at the 4 position of the 9-(((4-X-but-2-ynyloxy)methyl)-1,2,3-triazolyl)-substituent was synthesized. The copper-catalyzed three-component A3-coupling reaction of 9-(((4-prop-2-ynyloxy)methyl)-1,2,3-triazolyl)- substituted cinchona alkaloid derivatives with secondary amines and formaldehyde was the main route of synthesis. The present study attempted to examine the antibacterial properties of 9-substituted 9-desoxyquinine-derived compounds and their antibacterial activity against pathogenic bacterial strains, e.g., Staphylococcus aureus, Bacillus subtillis, Bacillus cereus, and Escherichia coli. The difference in the antibacterial activity profile of diastereoisomeric 9-(((4-X-but-2-ynyloxy)methyl)-1,2,3-triazolyl)-substituted derivatives of cinchona alkaloids indicated the importance of the nature of nitrogen substituents in the molecules. In a concentration-dependent pattern, (9R)- and (9S)- (((4-asocan-1yl)-but-2-ynyl-oxy)methyl)-1,2,3-triazolyl)-substituted compounds demonstrated considerable biofilm-inhibitory efficacy against the S. aureus bacterial strain. A detailed study of the molecular interactions with the targeted protein MurB was performed using docking simulations, and the obtained results are quite promising.

Cinchona alkaloids are naturally occurring chiral molecules that have emerged as catalysts in asymmetric organocatalysis especially in enantioselective transformations because of their inherent chirality and unique structural features. Immobilizing these alkaloids on polymeric supports has significantly influenced their use in catalysis. Polymer-anchored cinchona alkaloids combine the catalytic efficacy of cinchona derivatives with additional benefits of polymer chain, such as ease of recovery, recyclability, reusability, and reduced environmental impact. These polymer-supported cinchona alkaloids have found wide applications in enantioselective reactions such as Michael addition, aldol condensations, Henry reaction, dimerization reaction, dihydroxylation, and benzylation. Various strategies have been employed for anchoring cinchona alkaloids onto polymers, including covalent attachment of alkaloids in the polymer side chain or main chain, and ionic attachment of alkaloids via quaternization in the main chain or side chain of polymer. This review focuses on the various synthetic methodologies for the preparation of polymer-anchored cinchona alkaloids and their application in numerous asymmetric transformations.

Novel peptides based on common amino acid building blocks may serve as possible drug candidates; however, their flexible structures may require stabilization via the incorporation of conformational constraints. The insertion of unusual amino acids is a feasible option that may provide improved pharmacokinetic and pharmacodynamic properties of such peptide-type drugs. The stereochemical purity of these kinds of building blocks must be verified by an efficient separation technique, such as high-performance liquid chromatography. Here, we present and discuss the results of the stereoselective separation mechanism of ß-methylated phenylalanine (ß-MePhe), tyrosine (ß-MeTyr), 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (ß-MeTic), and cyclohexylalanine (ß-MeCha) together with non-methylated Phe, Tyr, Tic, and Cha applying Cinchona alkaloid-based chiral stationary phases (CSPs). The studied zwitterionic CSPs acting as ion exchangers provided optimal performance in the polar ionic mode when methanol or a mixture of methanol and acetonitrile was utilized as the mobile phase together with organic acid and base additives. It was found that the basicity of small amines applied as mobile phase additives did not directly influence the chromatographic ion exchange concept. However, the size of the amines and their concentration led to a reduced retention time following the principles of ion exchange chromatography. On the basis of a systematic study of the effects of the eluent composition on the chromatographic behavior, important structure–retention and enantioselectivity relationships could be revealed. Through a temperature study, it has become evident that the composition of the eluent and the structure of analytes markedly affect the thermodynamic properties.

Complementary to enantioselective transformations of planar functionalities, catalytic desymmetrization of meso compounds is another fundamentally important strategy for asymmetric synthesis. However, experimentally established stereochemical models on how a chiral catalyst discriminates between two enantiotopic functional groups in the desymmetrization of a meso substrate are particularly lacking. This article describes our endeavor to elucidate the chemical mechanism and characterization of the active conformation of the cinchona alkaloid-derived catalyst for a desymmetrization of meso cyclic anhydrides via asymmetric alcoholysis. First, our kinetic studies indicate that the cinchona alkaloid-catalyzed alcoholysis proceeds by a general base catalysis mechanism. Furthermore, the active conformer of the cinchona alkaloid-derived catalyst DHQD-PHN was clarified by catalyst conformation studies with a designed, rigid cinchona alkaloid derivative as a probe. These key mechanistic insights enabled us to construct a stereochemical model to rationalize how DHQD-PHN differentiates the two enantiotopic carbonyl groups in the transition state of the asymmetric alcoholysis of meso cyclic anhydrides. This model not only is consistent with the sense of asymmetric induction of the asymmetric alcoholysis but also provides a rationale on how the catalyst tolerates a broad range of cyclic anhydrides. These mechanistic insights further guided us to develop a novel practical catalyst for the enantioselective alcoholysis of meso cyclic anhydrides.

Neurodegenerative diseases (NDs), like Alzheimer’s disease (AD), present immense global health challenges, marked by progressive and irreversible neuronal loss. While many studies have reported the neuroprotective potential of various phytochemicals, the neurotherapeutic relevance of alkaloids, like cinchonine remains largely unexplored. This study for the first time investigates cinchonine, a natural Cinchona alkaloid with reported antioxidant, anti-inflammatory, and amyloid-inhibitory properties, for its interaction with human transferrin (hTf), a glycoprotein central to iron homeostasis and neuroprotection employing a combination of computational and experimental approaches. UV-Vis spectroscopy revealed significant changes in hTf’s absorbance upon cinchonine binding, confirming stable protein-ligand complex formation, with a binding constant ( K ) of 0.7 × 10 5 M − 1 . Fluorescence binding assay further validated the formation of a stable protein-ligand complex. Cinchonine binds with hTf with a binding constant ( K ) of 0.4 × 10 6 M − 1 , signifying the strength of interaction. Molecular docking pinpointed cinchonine’s specific binding site on hTf with a binding affinity of − 6.9 kcal/mol and its interactions with critical residues like Thr392. These findings were reinforced by molecular dynamics (MD) simulations and MM-PBSA, which showcased the stability and conformational integrity of the hTf-cinchonine complex over time. Additionally, hydrogen bonding and free energy analyses provided deeper insights into the molecular basis of the protein-ligand complex. All the findings imply the formation of a stable hTf-cinchonine complex. This study underscores cinchonine’s potential as a therapeutic lead, generating hypotheses for future experimental validation of its efficacy in preventing or mitigating NDs.

Among all the malaria parasites, P. falciparum is the most predominant species which has developed drug resistance against most of the commercial anti-malarial drugs. Thus, finding a new molecule for the inhibition of enzymes of P. falciparum is the pharmacological challenge in present era. Herein, ten novel molecules have been designed with an amalgamation of cinchonidine, carbohydrate moiety and triazole ring by utilizing copper-catalyzed click reaction of cinchonidine-derived azide and clickable glycosyl alkynes. The molecular docking of developed molecules showed promising results for plasmepsin inhibition in the form of effective binding with target proteins.

β-thalassemias are among the most common inherited hemoglobinopathies worldwide and are the result of autosomal mutations in the gene encoding β-globin, causing an absence or low-level production of adult hemoglobin (HbA). Induction of fetal hemoglobin (HbF) is considered to be of key importance for the development of therapeutic protocols for β-thalassemia and novel HbF inducers need to be proposed for pre-clinical development. The main purpose on this study was to analyze Cinchona alkaloids (cinchonidine, quinidine and cinchonine) as natural HbF-inducing agents in human erythroid cells. The analytical methods employed were Reverse Transcription quantitative real-time PCR (RT-qPCR) (for quantification of γ-globin mRNA) and High Performance Liquid Chromatography (HPLC) (for analysis of the hemoglobin pattern). After an initial analysis using the K562 cell line as an experimental model system, showing induction of hemoglobin and γ-globin mRNA, we verified whether the two more active compounds, cinchonidine and quinidine, were able to induce HbF in erythroid progenitor cells isolated from β-thalassemia patients. The data obtained demonstrate that cinchonidine and quinidine are potent inducers of γ-globin mRNA and HbF in erythroid progenitor cells isolated from nine β-thalassemia patients. In addition, both compounds were found to synergize with the HbF inducer sirolimus for maximal production of HbF. The data obtained strongly indicate that these compounds deserve consideration in the development of pre-clinical approaches for therapeutic protocols of β-thalassemia.

Background Cancer cells are known to over-express TRAF6 that is critical for both AKT and TAK1 activations. The Really Interesting New Gene (RING) domain of TRAF6 is believed to be responsible for the E3 ligase activity, ZINC fingers of TRAF6 provide critical support for the activity of the RING domain which is critical for both AKT and TAK1 activations. Methods We employed computational docking program to identify small molecules that could effectively and competitively bind with the RING domain of TRAF6, which is believed to be responsible for its E3 ligase activity. MTT assay and flow cytometry were employed to analyze apoptosis of cancer cells. Signaling pathways were detected using immunoprecipitation and western blotting, and immunofluorescence was pursued to assess the nature of binding of cinchonine to TRAF6. We also performed animal experiments to test effect of cinchonine in vivo. Results Cinchonine, a naturally occurring Cinchona alkaloid identified from the docking study, could bind to TRAF6 in HeLa and A549 cells and induce apoptosis of these cancer cells. We found that AKT ubiquitination and phosphorylation as well as phosphorylation of TAK1 were decreased. These activities would lead to subsequent suppression anti-apoptotic protein Bcl-2, while elevating pro-apoptotic protein Bax. Immunofluorescence staining unambiguously demonstrated the binding of cinchonine specifically at the RING domain of TRAF6 in cells, thereby validating the computational modeling. Animal experiments showed that cinchonine could suppress tumor growth in mice without showing significant acute toxicity. Conclusion These investigations suggest that through competitive binding with the RING domain of TRAF6, cinchonine could induce apoptosis via inhibiting AKT and TAK1 signaling pathways.

Polar-ionic and hydro-organic mobile phase mode of high-performance liquid chromatographic separations of 23 sterically constrained primary β(3)-amino acid enantiomers containing, alkyl, aryl or heteroaryl side-chains were carried out by using newly developed Cinchona alkaloid-based zwitterionic chiral selectors and the stationary phases Chiralpak ZWIX(+)™ and ZWIX(-)™. In the polar-ionic mode, the effects of the composition of the bulk solvent and the natures of the co- and counter-ions, while in the hydro-organic mode, the effects of the pH, the counter-ion concentration and the structures of the analytes were investigated. The separations of the enantiomers of these 23 primary β(3)-amino acids, which can be classified as a series of quasi- (pseudo-) homologs, were optimized in both chromatographic modes. The elution sequence was determined in most cases and a reversal of elution order on ZWIX(+)™ and ZWIX(-)™ column was observed. On the basis of this intermolecular recognition model between the selectors and the given enantiomers an indirect assignment of the resolved enantiomer via chromatography is proposed.

Detailed investigations concerning the organocatalytic (asymmetric) α-azidation of prochiral β-ketoesters were carried out. It was shown that the racemic version of such a reaction can either be carried out under oxidative conditions using TMSN3 as the azide-source with quaternary ammonium iodides as the catalysts, or by using hypervalent iodine-based electrophilic azide-transfer reagents with different organocatalysts. In addition, the latter strategy could also be carried out with modest enantioselectivities when using simple cinchona alkaloid catalysts, albeit with relatively low yields.