(3S)-N-(L-Aminoacyl)-1,2,3,4-tetrahydroisoquinolines, a class of novel antithrombotic agents: synthesis, bioassay, 3D QSAR, and ADME analysis

Synthesis of Polycyclic Tetrahydroisoquinolines and Tetrahydrobenzo[d]azepines from Polymer-Supported Allylglycine

Herein, we report a multistep synthesis of polycyclic tetrahydroisoquinolines and tetrahydrobenzo[d]azepines starting from Wang resin-immobilized allylglycine. After sulfonylation with 2/4-nitrobenzenesulfonyl chlorides, Mitsunobu alkylation with various phenylalkynols yielded the corresponding (phenylprop-2-yn-1-yl)-sulfonamides. "Interior" ring-closure enyne metathesis (RCEM) using a Grubbs catalyst second generation (Ru2) yielded functionalized tetrahydroisoquinoline/tetrahydrobenzo[d]azepine intermediates. "East-side" [4 + 2] cycloaddition with representative dienophiles was followed by the "west-side" construction of different heterocycles using various electrophiles to finally furnish a set of novel molecular frameworks bearing fused [6 + 6] or [6 + 7] rings. The developed methodology enables the facile parallel synthesis of novel, pharmacologically promising compounds derived from privileged scaffolds.

In silico discovery of SARS-CoV-2 main protease inhibitors from the carboline and quinoline database

Aim: SARS-CoV-2 caused more than 3.8 million deaths according to the WHO. In this urgent circumstance, we aimed at screening out potential inhibitors targeting the main protease of SARS-CoV-2. Materials & methods: An in-house carboline and quinoline database including carboline, quinoline and their derivatives was established. A virtual screening in carboline and quinoline database, 50 ns molecular dynamics simulations and molecular mechanics Poisson−Boltzmann surface area calculations were carried out. Results: The top 12 molecules were screened out preliminarily. The molecular mechanics Poisson−Boltzmann surface area ranking showed that p59_7m, p12_7e, p59_7k stood out with the lowest binding energies of -24.20, -17.98, -17.67 kcal/mol, respectively. Conclusion: The study provides powerful in silico results that indicate the selected molecules are valuable for further evaluation as SARS-CoV-2 main protease inhibitors.

Synthesis, biological evaluation and docking study of a new series of di-substituted benzoxazole derivatives as selective COX-2 inhibitors and anti-inflammatory agents

A new series of substituted-N-(3,4-dimethoxyphenyl)-benzoxazole derivatives 13a-13p was synthesized and evaluated in vitro for their COX (I and II) inhibitory activity, in vivo anti-inflammatory and ulcerogenic potential. Compounds 13d, 13h, 13k, 13l and 13n exhibited significant COX-2 inhibitory activity and selectivity towards COX-2 over COX-1. These selected compounds were screened for their in vivo anti-inflammatory activity by carrageenan induced rat paw edema method. Among these compounds, 13d was the most promising analogs of the series with percent inhibition of 84.09 and IC₅₀ value of 0.04 µM and 1.02 µM (COX-2 and COX-1) respectively. Furthermore, ulcerogenic study was performed and tested compounds (13d, 13h, 13k, 13l) demonstrated a significant gastric tolerance than ibuprofen. Molecular docking study was also performed with resolved crystal structure of COX-2 to understand the binding mechanisms of newly synthesized inhibitors in the active site of COX-2 enzyme and the results were found to be concordant with the biological evaluation studies of the compounds. These newly synthesized inhibitors also showed acceptable pharmacokinetic profile in the in silico ADME/T analyses.

Docking based design of diastereoisomeric MTCA as GPIIb/IIIa receptor inhibitor

In GPIIb/IIIa mediated arterial thrombosis platelet activation plays a central role. To discover platelet activation inhibitor the pharmacophores of GPIIb/IIIa receptor inhibitors and anti-thrombotic agents were analyzed. This led to the design of (1R,3S)- and (1S,3S)-1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acids as GPIIb/IIIa inhibitors. Comparing to (1S,3S)-isomer (1R,3S)-isomer had lower cdocker interaction energy. AFM image showed that the minimal effective concentration of (1S,3S)-isomer and (1R,3S)-isomer inhibiting platelet activation were 10^-5 M and 10^-6 M, respectively. In vivo 1 μmol/kg of oral (1S,3S)-isomer effectively inhibited the rats to form arterial thrombus and down regulated GPIIb/IIIa expression, but the activities were significantly lower than those of 1 μmol/kg of oral (1R,3S)-isomer. Both (1S,3S)-isomer and (1R,3S)-isomer can be safely used for structural modifications, but (1R,3S)-isomer should be superior to (1S,3S)-isomer.

DHDMIQK(KAP): a novel nano-delivery system of dihydroxyl-tetrahydro-isoquinoline-3-carboxylic acid and KPAK towards the thrombus

Vascular thrombosis is a major risk of the onset of stroke and so novel therapeutic candidates have been attracting interest. In this context, here docking based computer assisted screening and mesoscale simulation were used to design N-[(S)-6,7-dihydroxy-1,1-dimethyl-1,2,3,4-tetrahydroisoquinoline-3-carbonyl]-Lys(Pro-Ala-Lys), DHDMIQK(KAP), for inhibiting P-selectin expression. In vitro, 1 nM of DHDMIQK(KAP) effectively down-regulated P-selectin expression. In water, in rat plasma and in the solid state DHDMIQK(KAP) formed nanoparticles of a size capable of suitable delivery in the blood circulation. FT-MS and NOESY 2D NMR spectra showed DHDMIQK(KAP) formed hexamers, identified the intermolecular interactions of the hexamer, and assigned the hexamer a butterfly like conformation. Transmission electron microscopy, scanning electron microscopy and atomic force microscopy (AFM) imaged DHDMIQK(KAP) forming size-suitable nanoparticles for safe delivery in the blood circulation. In particular, AFM images showed that the nanoparticles effectively adhered onto the surfaces of the platelets. In vivo DHDMIQK(KAP) lysed the thrombus and inhibited thrombosis with a minimal effective dose of 0.01 nmol kg^-1. FT-MS spectrum analyses defined a specific distribution of DHDMIQK(KAP) in the thrombus, but not in the blood and vital organs. Therefore, DHDMIQK(KAP) should be a novel nano-delivery system of 6,7-dihydroxyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid and KPAK to target the thrombus.

Diversity-oriented synthesis of medicinally important 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) derivatives and higher analogs

1,2,3,4-Tetrahydroisoquinoline-3-carboxylic acid (Tic) is a constrained analog of phenylalanine (Phe). The Tic unit has been identified as a core structural element present in several peptide-based drugs and forms an integral part of various biologically active compounds. This report covers the biological significance of the Tic core and provides a detailed account of various synthetic approaches available for the construction of Tic derivatives. Along with the traditional methods such as the Pictet-Spengler and Bischler-Nepieralski reactions, we cover various recent approaches such as enyne metathesis, [2 + 2 + 2] cycloaddition and the Diels-Alder reaction to generate Tic derivatives. In addition, syntheses of higher analogs of Tic are also discussed.

Advances in computationally modeling human oral bioavailability

Although significant progress has been made in experimental high throughput screening (HTS) of ADME (absorption, distribution, metabolism, excretion) and pharmacokinetic properties, the ADME and Toxicity (ADME-Tox) in silico modeling is still indispensable in drug discovery as it can guide us to wisely select drug candidates prior to expensive ADME screenings and clinical trials. Compared to other ADME-Tox properties, human oral bioavailability (HOBA) is particularly important but extremely difficult to predict. In this paper, the advances in human oral bioavailability modeling will be reviewed. Moreover, our deep insight on how to construct more accurate and reliable HOBA QSAR and classification models will also discussed.

The application of tetrahydroisoquinoline-3-carbonyl-TARGD(F)F as an anti-thrombotic agent having dual mechanisms of action

Platelet surface glycoproteins P-selectin and GPIIb/IIIa are implicated in the formation of platelet-fibrin-leukocyte thrombus and platelet-fibrin-platelet thrombus, respectively. In the current study, taking N-(3S-tetrahydroisoquinoline-3-carbonyl)-Thr-Ala-Arg-Gly-Asp-(Phe)-Phe (IQCA-TAFF) as a model compound, the molecular modeling, synthesis, and an evaluation system for a novel anti-thrombotic agent were investigated. The synthesis of IQCA-TAFF was achieved by coupling 3S-tetrahydro-isoquinoline-3-carboxylic acid (IQCA) and Thr-Ala-Arg-Gly-Asp(Phe)-Phe (TAFF). The molecular modeling indicated that IQCA-TAFF was able to occupy the active site pocket of P-selectin with its IQCA moiety and to block GPIIb/IIIa fibrinogen-binding sites with its TAFF moiety, respectively. These are consistent with the dual inhibition of the expressions of P-selectin and GPIIb/IIIa, and with the in vitro anti-platelet aggregation activity of IQCA-TAFF. Besides, the dual suppression of P-selectin and GPIIb/IIIa leads to significant in vivo efficacy of IQCA-TAFF, 500-fold higher than those of IQCA and TAFF, respectively. Transmission electron microscopy (TEM) images indicated that in water, IQCA-TAFF concentration-dependently formed nano-globes. The molecular modeling, in vitro bioassay, in vivo bioassay, action mechanism investigation, and nano-image visualization together constitute a model system to characterize the anti-thrombotic agent capable of simultaneously inhibiting P-selectin and GPIIb/IIIa mediated thrombosis.

Studies on the enantiomers of ZJM-289: synthesis and biological evaluation of antiplatelet, antithrombotic and neuroprotective activities

ZJM-289 is a potent racemic agent which inhibits both platelet aggregation and thrombosis superior to a known anti-ischemic stroke drug 3-n-butylphthalide (NBP). Herein, the enantiomers of ZJM-289, (S)-ZJM-289 and (R)-ZJM-289, were synthesized and evaluated for their biological activities. It was observed that the two enantiomers appeared to be almost as effective as ZJM-289 in inhibiting platelet aggregation in vitro and thrombus formation in vivo. Moreover, like ZJM-289, its enantiomers could regulate the ratio of thromboxane B(2) (TXB(2)) and 6-keto-prostaglandin F(1α), and enhanced levels of nitric oxide (NO), cAMP and cGMP, suggesting that the anti-platelet and antithrombotic activities of the enantiomers and ZJM-289 are associated with both the arachidonic acid cascade and cGMP-NO signal pathway. Furthermore, it was found that oral administration of the enantiomers and ZJM-289 for three days significantly reduced the infarct size, brain water content and neurological deficit in rats after cerebral ischemia reperfusion. Importantly, the two enantiomers equally improved blood flow in the ischemic stroke model and modulated endothelial function through releasing moderate levels of NO, which might, at least partially, contribute to their neuroprotection. Collectively, the present study demonstrates that the two enantiomers are as potent as ZJM-289 in inhibition of platelet aggregation and thrombosis and in neuroprotection, and (S)-ZJM-289 shows somewhat better effects than (R)-ZJM-289 and ZJM-289 in a few cases. These findings may provide new insights into the development of therapeutic agents like ZJM-289 for the intervention of thrombosis-related ischemic stroke.

pH-Dependent nanostructure based on isoquinoline-cyclodextrin conjugate for thrombosis therapy

The modification of 3S-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (THIQA) with β-cyclodextrin (β-CD) provides an oral antithrombotic agent, 6-(3'S-isoquinoline-3'-carboxylaminoethylamino)-6-deoxy-β-CD (THIQA-β-CD). In aqueous solution THIQA-β-CD undergoes intermolecular inclusion complexation and forms pH-dependent nanostructures. The morphological feature of THIQA-β-CD is a nanocloud consisting of numerous particles that are 5 nm-6 nm in diameter at pH 3.0. The nanocloud switches to a nanorod ranging from 100 nm to 385 nm in length at pH 7.2, then to nanowires of 50 nm to 530 nm in length at pH 10.1. THIQA-β-CD, which has unusual nanostructures, offers enhanced stability in blood. Inhibition of thrombin-induced platelet aggregation in vitro and demonstrated antithrombotic efficacy in vivo. This investigation demonstrated that the modification of THIQA with β-CD is a promising approach for clinical therapy of thrombus disease. The pH-dependent nanostructures of conjugate provide the desired in vivo antithrombotic activity and in vitro stability in blood.

FROM THE CLINICAL EDITOR

This study a demonstrates that the modification of 3S-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (THIQA) with beta-cyclodextrin, which leads to pH dependent nanostructure formation, is a promising approach for clinical therapy of thrombotic disease.

2,3-Diamino acid modifying 3S-tetrahydroisoquinoline-3-carboxylic acids: leading to a class of novel agents with highly unfolded conformation, selective in vitro anti-platelet aggregation and potent in vivo anti-thrombotic activity

In the preparation of anti-thrombotic agents the 2- and 3-positions of 3S-tetra-hydroisoquinoline-3-carboxylic acid (THIQA) were simultaneously modified with amino acids to form 20 novel N-(3S-N-aminoacyl-1,2,3,4-tetrahydroisoquinoline-3-carbonyl)amino acids (8a-t). On an in vitro platelet aggregation model 8a-t selectively inhibit ADP-induced platelet aggregation and their IC(50) values are leas than 3.5 nM. On an extracorporeal circulation of arterioveinos cannula model of rats both orally and intraveously effective doses of 8a-t are less than 30 nmol/kg. Cerius(2) based stereoview of explores 8a-t having highly unfolded conformation. 3D QSAR analysis gives the importance of the unfolded conformation to high in vitro anti-platelet aggregation and in vivo anti-thrombotic potency rational understanding.