Investigation of platelet aggregation inhibitory activity by phenyl amides and esters of piperidinecarboxylic acids

Synthesis and antithrombotic activity of 1-benzyl-N'-benzylidenepiperidine-3-carbohydrazide derivatives

: Platelet aggregation inhibition and interfering with clot formation are essential tools for antithrombotic therapy and there is a need for discovering new antithrombotic agents. In this study, we synthesized a series of benzylidenepiperidine-3-carbohydrazide derivatives (1f-11f), bearing various selected substituents on both the piperidine ring nitrogen and the hydrazide nitrogen. The synthesized compounds were characterized by FTIR, HNMR spectroscopic techniques, CHN/O elemental analysis and electrospray ionization mass spectra. All new 1-benzyl-N'-benzylidenepiperidine-3-carbohydrazides were evaluated for their antiplatelet aggregation activities (against platelet aggregation induced by AA, ADP and collagen separately) and anticoagulant activities [protrombin time (PT) and partial thromboplastin time (PTT)]. Antiplatelet aggregation activity of the new derivatives was measured using human plasma on an APACT 4004 aggregometer. All the compounds were mainly effective on ADP pathway of platelet aggregation compared with collagen and AA pathways. The most potent compound on platelet aggregation induced by ADP is compound 2f with 87% aggregation inhibition activity at 0.5 mmol/l concentration. The synthesized compounds were further investigated for their anticoagulant action via the two PT and PTT models. They all showed higher PT and PTT values compared with the blank control sample. The most potent compounds are 5f, 6f, 7f and 1f. All compounds were obtained in good yield and further evaluated for their antiplatelet and anticoagulant activity.

Synthesis and biological evaluation of direct thrombin inhibitors bearing 4-(piperidin-1-yl)pyridine at the P1 position with potent anticoagulant activity

The design and synthesis of a new class of nonpeptide direct thrombin inhibitors, built on the structure of 1-(pyridin-4-yl)piperidine-4-carboxamide, are described. Starting from a strongly basic 1-amidinopiperidine derivative (6) showing poor thrombin (fIIa) and factor Xa (fXa) inhibition activities, anti-fIIa activity and artificial membrane permeability were considerably improved by optimizing the basic P1 and the X-substituted phenyl P4 binding moieties. Structure-activity relationship studies, usefully complemented with molecular modeling results, led us to identify compound 13b, which showed excellent fIIa inhibition (Ki = 6 nM), weak anti-Xa activity (Ki = 5.64 μM), and remarkable selectivity over other serine proteases (e.g., trypsin). Compound 13b showed in vitro anticoagulant activity in the low micromolar range and significant membrane permeability. In mice (ex vivo), 13b demonstrated anticoagulant effects at 2 h after oral dosing (100 mg·kg(-1)), with a significant 43% prolongation of the activated partial thromboplastin time (aPTT), over controls (P < 0.05).

Piperazinyl-glutamate-pyrimidines as potent P2Y12 antagonists for inhibition of platelet aggregation

Piperazinyl-glutamate-pyrimidines were prepared with oxygen, nitrogen, and sulfur substitution at the 4-position of the pyrimidine leading to highly potent P2Y12 antagonists. In particular, 4-substituted piperidine-4-pyrimidines provided compounds with exceptional potency. Pharmacokinetic and physicochemical properties were fine-tuned through modifications at the 4-position of the piperidine ring leading to compounds with good human PRP potency, selectivity, clearance and oral bioavailability.

Piperazinyl-glutamate-pyridines as potent orally bioavailable P2Y12 antagonists for inhibition of platelet aggregation

Polymer-assisted solution-phase (PASP) parallel library synthesis was used to discover a piperazinyl-glutamate-pyridine as a P2Y(12) antagonist. Exploitation of this lead provided compounds with excellent inhibition of platelet aggregation as measured in a human platelet rich plasma (PRP) assay. Pharmacokinetic and physiochemical properties were optimized leading to compound (4S)-4-[({4-[4-(methoxymethyl)piperidin-1-yl]-6-phenylpyridin-2-yl}carbonyl)amino]-5-oxo-5-{4-[(pentyloxy)carbonyl]piperazin-1-yl}pentanoic acid 22J with good human PRP potency, selectivity, in vivo efficacy and oral bioavailability.

Synthesis and inotropic evaluation of 1-substituted-N-(4,5-dihydro-1-methyl-[1,2,4]triazolo[4,3-a]quinolin-7-yl)piperidine-4-carboxamides

A series of 1-substituted-N-(4,5-dihydro-1-methyl-[1,2,4]triazolo[4,3-a]quinolin-7-yl) piperidine-4-carboxamides has been synthesized and evaluated for positive inotropic activity by measuring left atrium stroke volume in isolated rabbit-heart preparations. Some of these derivatives exhibited favorable activity compared with the standard drug, milrinone, among which 1-(2-fluorobenzyl)-N-(4,5-dihydro-1-methyl-[1,2,4]triazolo[4,3-a]quinolin-7-yl)piperidine-4-carboxamide 6a was the most potent, increasing stroke volume by 11.92+/-0.35% (milrinone: 6.36+/-0.13%) at 1x10(-4)M.

QSAR studies of paeonol analogues for inhibition of platelet aggregation

Various paeonol analogues were synthesized and tested in vitro as inhibitors of platelet aggregation. Structural properties (or descriptors) of paeonol analogues were calculated and the structure-activity relationships were determined. Several multiple linear and nonlinear regression models and back-propagation neural network model were tested and the latter using relative positive charge, hydration energy, and hydrophilic factor as inputs gave the best data fitting with R2 = 0.89 and q(pre)2 = 0.66. The correlation coefficient between antiplatelet inhibition activity with an interaction energy between the paeonol compounds with COX-1 enzyme is only 0.39.

Lipophilicity-related inhibition of blood platelet aggregation by nipecotic acid anilides

Using N-[4-(hexyloxy)phenyl]piperidine-3-carboxamide (17c) as a structural lead, a number of isomers, derivatives, and ring-opened analogs were synthesized and tested for their ability to block the in vitro aggregation of human platelets induced by adenosine 5'-diphosphate (ADP). For the most active compounds, inhibition of the platelet aggregation triggered by arachidonic acid (AA) and ADP-induced intraplatelet calcium mobilization was also demonstrated. Based on quantitative structure-activity relationships (QSARs), we proved the impact of hydrophobicity on antiplatelet activity by a nonlinear (parabolic or bilinear) relationship between pIC(50) and lipophilicity, as assessed by RP-HPLC capacity factors and ClogP (i.e. calculated 1-octanol-water partition coefficients). This study highlighted the following additional SARs: quasi-isolipophilic isomers of 17c (isonipecotanilides and pipecolinanilides) and ring-opened analogs (e.g. anilide of beta-alanine) exhibited lower antiplatelet activity; methylation of the piperidine nitrogen of 17c has no effect, whereas alkylation with an n-propyl group decreases the activity by a factor of approximately 2, most likely due to a conformation-dependent decrease in lipophilicity.