Search Results (90)

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. Full article

The palladium-catalyzed cross-coupling reaction used for carbon–carbon bond formation is one of the most commonly applied reactions in modern organic synthesis. In this work, a concise strategy was developed for constructing the tetrahydroisoquinoline core, a key structural motif found in many biologically active compounds. This method involves the palladium-catalyzed intramolecular coupling of aryl iodides with ester enolates generated in the presence of K₃PO₄ as a base, resulting in the formation of the tetrahydroisoquinoline ring with an exceptionally high yield of 84%. Full article

The tetrahydroisoquinoline skeleton is a pharmacologically significant core structure containing chiral centers, making enantiomeric separation crucial due to the potentially distinct biological effects of each enantiomer. In this study, laudanosine (N-methyl-tetrahydropapaverine) and its three derivatives (6′-bromo-laudanosine, norlaudanosine, and N-propyl-norlaudanosine) were synthesized and used as model compounds to investigate chiral recognition mechanisms. Screening over twenty cyclodextrins (CyDs) as chiral selectors in capillary electrophoresis (CE), we found anionic CyDs to be the most effective, with sulfated-γ-CyD (S-γ-CyD) achieving a maximum R_s of 10.5 for laudanosine. Notably, octakis-(6-deoxy-6-(2-carboxyethyl)-thio)-γ-CyD (sugammadex, SGX), heptakis-(2,3-O-diacetyl-6-O-sulfo)-β-CD (HDAS), heptakis-(2,3-O-dimethyl-6-O-sulfo)-β-CD (HDMS), and octakis-(2,3-O-dimethyl-6-O-sulfo)-γ-CD (ODMS) provided excellent enantioseparation for all four analytes. Following HPLC screening on CyD-based and polysaccharide-based chiral stationary phases, semi-preparative HPLC methods using amylose and cellulose-based columns were optimized to isolate enantiomers. The purity of the isolated enantiomers was evaluated by HPLC, and their configurations were confirmed via circular dichroism spectroscopy. The isolated enantiomers allowed us to explore enantiomer migration order reversals in CE and enantiomer elution order reversal in HPLC. Further ¹H and 2D ROESY NMR experiments provided atomic-level insights into enantioselective complex formation, confirming enantiomer differentiation by SGX and elucidating the inclusion complex structure, where the ring C immersion into the CyD cavity is prevalent. Full article

A visible-light-mediated strategy for the direct oxygenation of N-substituted tetrahydroisoquinolines and isoindolines to the corresponding benzo-fused lactams under clean conditions without using any external photocatalysts has been developed. The reaction was performed in the presence of a catalytic amount of base and oxygen. Mechanistic studies reveal that the reaction is initiated by the substrates themselves as photosensitizers. Additionally, BHT could be used as a buffer-like additive to improve reaction selectivity and product yield in this photo-oxidation process. Full article

Herein, we take an underground natural gas storage in the Ordos Basin as an example to explore the influence of temperature, CO₂ flow rate, CO₂ partial pressure, and chloride ion concentration on the corrosion rate of N80 and P110 steels in CaCl₂ brine type. Meanwhile, in order to reduce the amount of chemical corrosion inhibitors and improve performance, a novel corrosion inhibitor with a quinoline quaternary ammonium structure named YS-QB was synthesized from 1-methyl-1,2,3,4-tetrahydroisoquinoline, epichlorohydrin, and oleic acid amide propyl dimethylamine. Under normal and high-pressure environments, YS-QB exhibits a superior corrosion inhibition effect to the market product of CX-1. In order to further reduce the amount of corrosion inhibitor and improve the corrosion inhibition effect, orthogonal experiments were conducted to optimize the formula system, and the optimal composite system was finally obtained by forming YS-QB, propargyl alcohol, hexamethylenetetramine, and isopropanol in a mass ratio of 12:1:1:2. At 80 °C, a dosage of 30 mg/L can suppress the CO₂ corrosion rate below 0.076 mm/a, while a dosage of 60 mg/L can suppress the CO₂ corrosion rate below 0.076 mm/a at a high-pressure environment of 120 °C. Combining weightlessness and electrochemical experiments, it is found that the composite corrosion inhibitor performs best when the dosage reached 100 mg/L, and a further increase in the dosage weakens the corrosion inhibition capacity. Based on the polarization curve changes with the dosage of the composite corrosion inhibitor, it can be determined that the final obtained composite corrosion inhibitor system was a cathodic corrosion inhibitor. Full article

Quercetin, a well-known flavonoid with significant medicinal potential, was derivatized at the C8 position with a tetrahydroisoquinoline (THIQ) moiety, and physicochemical and pharmacological properties, inhibition potential, antioxidant activity, and cytotoxicity of new compounds were evaluated. Physicochemical and pharmacological properties, including lipophilicity, membrane permeability, and P-glycoprotein substrate affinity, were assessed theoretically using the SwissADME software. The metal-chelating ability of the new compounds was evaluated on metal ions Fe²⁺, Zn²⁺, and Cu²⁺, whose homeostasis disruption is linked to the development of Alzheimer’s disease. Inhibition potential was tested on the cholinergic enzymes acetylcholinesterase and butyrylcholinesterase, as well as Na⁺, K⁺-ATPase, an enzyme commonly overexpressed in tumours. Antioxidant potential was assessed using the DPPH assay. Cytotoxicity studies were conducted on healthy MRC-5 cells and three cancer cell lines: HeLa, MDA-231, and MDA-468. The results indicated that derivatization of quercetin with THIQ yielded compounds with lower toxicity, preserved chelating ability, improved antioxidant potential, increased selectivity toward the cholinergic enzyme butyrylcholinesterase, and enhanced inhibition potential toward Na⁺, K⁺-ATPase and butyrylcholinesterase compared to quercetin alone. Therefore, the synthesized derivatives represent compounds with an improved profile and could be promising candidates for further optimization in developing drugs for neurodegenerative and cancer diseases. Full article

Enantiopure tetrahydroisoquinolines (THIQs), recognized as privileged skeletal structures in natural alkaloids, have attracted considerable attention from chemists due to their biological and pharmacological activities. Synthetic strategies for optically active THIQs have been rapidly and extensively developed in the past decades. In view of simplicity and atom economy, asymmetric reduction of N-heteroaromatics, imines, enamines, and iminium salts containing an isoquinoline (IQ) moiety should be the preferred approaches to obtain chiral THIQs. This review focuses on recent advances in the catalytic asymmetric synthesis of enantiopure THIQs via asymmetric reduction, including asymmetric hydrogenation, transfer hydrogenation, reductive amination, and deracemization. Highly enantioselective synthesis of THIQs was achieved via transition-metal-catalyzed asymmetric reduction and organocatalytic asymmetric reduction utilizing either catalyst activation or substrate activation strategy. Despite much progress in the enantioselective synthesis of THIQs, there still remain considerable opportunities and challenges for progress and developments in this field of research, particularly in the development of asymmetric catalytic systems for the direct reduction of IQs. Full article

Cardiovascular disease is the first cause of death worldwide and kills more people each year than any other cause of death. N, N-dimethylaniline-heliamine (DH), a synthetic tetrahydroisoquinoline alkaloid, has shown notable antiarrhythmic activity. However, the metabolic processes and pharmacokinetic characteristics of DH in rats have not been studied. This study aims to identify its metabolites, as well as develop and validate a rapid and efficient bioanalytical method for quantifying DH in rat plasma over a wide range of concentrations. Its metabolites were characterized in silico, in vitro, and in vivo. A series of 16 metabolites were identified, of which 12 were phase I metabolites and 4 were phase II metabolites. A low probability of DH binding to DNA, protein, and glutathione is predicted by the in silico model. The main metabolic processes of DH were demethylation, dehydrogenation, glucuronidation, and sulfation. Concentration–time profiles were generated by analyzing the plasma, and the outcomes were analyzed via non-compartmental analysis to identify the pharmacokinetic parameters. Among the detected parameters were the volume of distribution, estimated at 126,728.09 ± 56,867.09 mL/kg, clearance at 30,148.65 ± 15,354.27 mL/h/kg, and absolute oral bioavailability at 16.11%. The plasma distribution volume of DH was substantially higher than the overall plasma volume of rats, which suggests that DH has a specific tissue distribution in rats. This study suggests that DH is appropriately bioavailable and excreted via a variety of routes and has low toxicity. Full article

Triazole derivatives of fluorescein-containing N,N-dimethylaminopropyl fragments and their ammonium salts were synthesized with yields of 74–85%. The resulting compounds exhibit fluorescent properties in the green region of the visible spectrum. The critical aggregation concentration (CAC) was estimated using a pyrene fluorescent probe corresponding to a range of 0.28–1.43 mM, and at concentrations above the CAC, the compounds form stable aggregates ranging from 165 to 202 nm. A relative quantum yield of 5–24% has been calculated based on fluorescence and UV spectra. The best value is shown by a derivative containing a tetradecyl substituent. When studying the photocatalytic properties of synthesized compounds through the reaction between N-substituted 1,2,3,4-tetrahydroisoquinoline and malonic ester, the mono-tetradecyl derivative demonstrated the best results. According to gas chromatography–mass spectrometry (GC-MS) data, the conversion of the initial heterocycle reached 95%. Therefore, these resulting compounds have the potential to act as an effective photocatalysts. Full article

Mechanochemistry has emerged as a potential alternative for organic transformations, leveraging substrate availability, stability, and reduced solvent use. Its high efficiency and eco-friendly profile have garnered significant attention, particularly in the pharmaceutical industry, where it is hailed as the most promising environmentally friendly method for organic synthesis. This approach harnesses mechanical energy to stimulate or accelerate chemical changes, offering a green and effective means to obtain organic molecules. We employed an innovative green and eco-friendly approach—mechanochemical, solvent-free, and heterogeneously catalyzed—to synthesize a series of new biofunctional hybrid molecules, specifically derivatives of biologically active 1,2,3,4-tetrahydroisoquinoline alkaloids. Our method involves a mechanochemically driven intramolecular α-amidoalkylation reaction. To facilitate this reaction under acidic conditions, we successfully utilized polyphosphoric acid on silica as a heterogeneous catalyst. This approach enables the rapid and straightforward synthesis of novel compounds without the generation of byproducts or waste. All newly obtained bio-functional hybrid compounds were fully characterized via ¹H, ¹³C NMR, UV, and mass spectral data. In our quest for environmentally sustainable synthesis methods, we made a significant breakthrough by synthesizing a series of innovative N-ibuprofen-substituted 1,2,3,4-tetrahydroisoquinolines through solvent-free mechanosynthesis. These novel derivatives offer exciting prospects for studying their biological properties and investigating correlations between structure and activity. Full article

Isoquinoline alkaloids constitute a substantial category of natural products, among which 1,2,3,4-tetrahydroisoquinoline (THIQ) holds significance. THIQ-based compounds, whether natural or synthetic, showcase a wide array of biological activities, demonstrating efficacy against diverse infectious pathogens and neurodegenerative disorders. Consequently, THIQ heterocyclic structures have garnered considerable interest within the scientific realm, driving the exploration and synthesis of novel THIQ derivatives with notable biological potential. In contrast, flurbiprofen falls under the category of nonsteroidal anti-inflammatory drugs (NSAIDs) and demonstrates both antipyretic and analgesic effects. Its potential extends beyond mere pain relief; it has been suggested for both local and systemic applications, such as inhibiting colon tumor growth and platelet aggregation. In our research, we focus on synthesizing novel N-flurbiprofen-substituted 1,2,3,4-tetrahydroisoquinolines. We explore novel methods for the amide cyclization, investigating the feasibility of utilizing new environmentally friendly reagents. Specifically, we examine the efficacy of strong protic acids that are immobilized on a silica gel as heterogeneous acid catalysts in intramolecular α-amidoalkylation reactions. These acid-supported silica gel systems are pivotal in acid-catalyzed synthetic processes, emerging as preferred options for producing novel organic compounds, aligning with eco-friendly practices. Our interest lies in applying this heterogeneous acid system on a silica gel as a “heterogeneous catalyst” to synthesize isoquinoline derivatives of flurbiprofen and elucidate the relationship between their structure and activity. When investigating the intramolecular α-amidoalkylation reaction, we conduct multiple experiments to determine the ideal reaction conditions. This involves altering solvents and acid reagents while considering the acid-catalyzed nature of the reaction. The novel compounds were successfully synthesized through an intramolecular α-amidoalkylation reaction. This synthesis method involved heating the reactants at 80 °C in dichloroethane, supplemented with a heterogeneous acid catalyst, PPA/SiO₂. The obtained compounds underwent full spectral characterization using ¹H and ¹³C NMR, IR spectroscopy, and mass analysis. Full article

A chemselective catalyst-free three-component 1,3-dipolar cycloaddition has been described. The unique polycyclic THPI and THIQs were creatively employed as dipolarophiles, which led to the formation of functionalized β-tetrahydrocarboline- and tetrahydroisoquinoline-fused spirooxindoles in 60–94% of yields with excellent diastereoselectivities (10: 1−>99: 1 dr). This reaction not only realizes a concise THPI- or THIQs-based 1,3-dipolar cycloaddition, but also provides a practical strategy for the construction of two distinctive spirooxindole skeletons. Full article

We have synthesized 22 C-1 functionalized-N-aryl-1,2,3,4-tetrahydroisoquinoline derivatives showing biological activities towards cholinergic enzymes. Synthesis was performed using visible-light-promoted photo-redox chemistry, starting from a common intermediate, and the application of this synthetic methodology drastically simplified synthetic routes and purification of desired compounds. All synthesized derivates were divided into four groups based on the substituents in the C-1 position, and their inhibition potencies towards two cholinergic enzymes, acetyl- and butyrylcholinesterase were evaluated. Most potent derivatives were selected, and kinetic analysis was further carried out to obtain insights into the mechanisms of inhibition of these two enzymes. Further validation of the mode of inhibition of cholinergic enzymes by the two most potent THIQ compounds, 3c and 3i, was performed using fluorescence-quenching titration studies. Molecular docking studies further confirmed the proposed mechanism of enzymes’ inhibition. In silico predictions of physicochemical properties, pharmacokinetics, drug-likeness, and medicinal chemistry friendliness of the selected most potent derivatives were performed using Swiss ADME tool. This was followed by UPLC-assisted log P determination and in vitro BBB permeability studies performed in order to assess the potential of the synthesized compounds to pass the BBB. Full article

Trabectedin (TRB) and Lurbinectedin (LUR) are alkaloid compounds originally isolated from Ecteinascidia turbinata with proven antitumoral activity. Both molecules are structural analogues that differ on the tetrahydroisoquinoline moiety of the C subunit in TRB, which is replaced by a tetrahydro-β-carboline in LUR. TRB is indicated for patients with relapsed ovarian cancer in combination with pegylated liposomal doxorubicin, as well as for advanced soft tissue sarcoma in adults in monotherapy. LUR was approved by the FDA in 2020 to treat metastatic small cell lung cancer. Herein, we systematically summarise the origin and structure of TRB and LUR, as well as the molecular mechanisms that they trigger to induce cell death in tumoral cells and supporting stroma cells of the tumoral microenvironment, and how these compounds regulate immune cell function and fate. Finally, the novel therapeutic venues that are currently under exploration, in combination with a plethora of different immunotherapeutic strategies or specific molecular-targeted inhibitors, are reviewed, with particular emphasis on the usage of immune checkpoint inhibitors, or other bioactive molecules that have shown synergistic effects in terms of tumour regression and ablation. These approaches intend to tackle the complexity of managing cancer patients in the context of precision medicine and the application of tailor-made strategies aiming at the reduction of undesired side effects. Full article

Through the Lilly Open Innovation Drug Discovery program (OIDD), we discovered five cationic bis(aryltriazol-4-yl)methyl)-6,7-dimethoxytetrahydroisoquinolinium derivatives that effectively inhibit human nicotinamide N-methyltransferase. Compounds 4a, 4c, and 4f demonstrated activity against hNNMT in enzymatic-based testing, with IC₅₀ values of 3.177 μM, 7.9 μM, and 4.477 μM, respectively. In cell-based testing, 4c and 4f inhibited the enzyme in HEK293 cells with an IC₅₀ value of 2.81 μM and 1.97 μM. Compound 4m inhibited hNNMT in the enzymatic-based assay by 98% at a concentration of 10 μM, with IC₅₀ of 1.011 μM in the cell-based assay. Through structure-activity relationship analysis, we found that the active compounds had electron-withdrawing substituents at the 4-position of the phenyl-triazole, while compounds containing bulky and electron-donating groups at the same position did not display any activity. The results of docking studies using AutoDock 4.2 showed that all active compounds had similar binding patterns at the NNMT active site. They occupied the nicotinamide binding site and about two-thirds of the S-adenosyl-L-methionine site. However, the SAR and docking results of 4g contradicted the compound’s inactivity. Nevertheless, the molecular docking studies provided insight into how the ligands interact with the protein and explained the activity of our compounds. Full article