Molecular determinants of the platelet aggregation inhibitory activity of carbamoylpiperidines

Abstract

A series of alpha,alpha'-bis[3-(N,N-dialkylcarbamoyl)piperidino]-p- xylenes were synthesized and tested for their inhibitory activity on ADP-induced aggregation of human platelets. A parabolic curve was obtained when log 1/C (activity) was plotted against log P (octanol/water partition coefficient). Using this as a model, a new analogue, alpha,alpha'-bis-[3-(N-methyl-N-butylcarbamoyl)piperidino]-p-xylen e (3g), was synthesized with a predicted IC50 of 25 microM. When this compound was subsequently evaluated, the IC50 was 22.1 +/- 5.5 microM, demonstrating the applicability of this model. The amide oxygen of the carbamoyl substituent appeared necessary for activity. Thus, for example, when the amide carbonyl group of 3a (IC50 = 44.5 microM) was reduced to CH2, the resulting compound 4 had a dramatically reduced activity, IC50 = 1565 microM. Compound 3a was resolved into (+) and (-) enantiomers and a meso (0) diastereomer using fractional crystallization, diastereomeric tartrate formation, and chiral HPLC. Compared to (-)-3a, the (+) isomer was 15 times more potent when ADP was the agonist and 19 times more active when collagen was used as the agonist. Molecular modeling of R,R- and S,S-3a using the SYBYL program was used to examine their interactions with phosphatidylinositol (PI). There was a better fit between PI and the R,R-3a with the energy of interaction being 17.6 kcal/mol less than that of the S,S-3a/PI complex. Although the absolute stereochemistry of individual enantiomers is not known, this study shows that R,R-3a interacts more favorably with PI than does S,S-3a and that (+)-3a is a more potent inhibitor of human platelet aggregation than (-)-3a. It is postulated that because of their lipophilicity, these compounds penetrate the platelet membrane and are then protonated at the pH of the cytosol. The protonated N then neutralizes the anionic charge on the membrane phosphoinositides, thereby rendering them less susceptible to hydrolysis by phospholipase C. Thus, the determinant parameters for optimum antiplatelet activity in 3-carbamoylpiperidines are (1) the amide carbonyl, (2) appropriate stereochemistry of the 3-substituent and (3) a log P value of about 4.5.

Investigation on the antiplatelet activity of pyrrolo[3,2-c]pyridine-containing compounds

“…In a preliminary analysis of the relationship between activity and lipophilicity (Altomare et al 2000), we observed that the activity of THPPs increased with increasing lipophilicity, up to a log P value of around 2, beyond which it remained quite constant. This was interpreted as a possible signal of a nonlinear (parabolic or bilinear) dependence of the antiplatelet activity on the lipophilicity, as had been demonstrated in a number of antiplatelet series (Feng et al 1992;Tanaka et al 1994Tanaka et al , 1996. We investigated the partitioning properties of all the derivatives by measuring polycratic capacity factors log k 0 w in RP-HPLC (Altomare et al 1993(Altomare et al , 1994, and comparing them with the octanol±water partition coefficients calculated with the Clog P software.…”

Prevalence of the prothrombin G20210A mutation among ischemic stroke patients

“…Prothrombin is a 72 kDa vitamin K-dependent glycoprotein formed in the liver, 6 it’s a precursor of the serine protease thrombin and play a significant role in the process of hemostasis and thrombosis. 7 Prothrombin gene mutation G20210A is a common prothrombotic single-nucleotide polymorphism.…”

Synthesis, antiplatelet aggregation activity, and molecular modeling study of novel substituted-piperazine analogues

“…As a consequence, the levels of IP 3 and of cytosolic Ca 2? concentrations, necessary for myosin phosphorylation and subsequent platelet activation, are reduced (Youssef and Al-Shafie, 1998;Heath et al, 2004;Feng et al, 1992;Dillingham et al, 1989). Phospholipases A 2 (PLA 2 s) catalyze the hydrolysis of glycerol-phospholipids at the sn-2 position and generate free fatty acids and lysophospholipids (Slotboom et al, 1982).…”