Synthesis And Inhibition Of Platelet Aggregation Research Of P2Y₁₂ Receptor Antagonists

Along with the social development, more and more people are suffered from the diseases associated, with their lifestyle. Cardiovascular disease is the leading cause of deaths worldwide according to WHO’s statistics. The causes of cardiovascular disease are diverse but atherosclerosis and/or hypertension are the most common. Additionally, aging also accounts for a number of physiological and morphological changes that alter cardiovascular function and subsequently increased risk of cardiovascular disease.Platelets aggregate plays very important roles in atherosclerosis. Studies show that platelets aggregate uses fibrinogen and von Willebrand factor (vWF) as a connecting agent. The most abundant platelet aggregation receptor is glycoprotein Ⅱb/Ⅲa (gpⅡb/Ⅲa) Activated platelets will adhere, to the collagen via glycoprotein (GP) Ⅰa. Aggregation and adhesion act together to form the platelet plug.Platelet aggregation is stimulated by ADP, thromboxane, and a2receptor-activation. Human platelets have three types of P2receptors:P2X1, P2Y1and P2Y12. After thoroughly explorations, scientists have documented only P2Y12is clinically correlated available.P2Y12belongs to the Gi class of a group of G protein-coupled (GPCR) purinergic receptors.P2Y12protein is found mainly but not exclusively on the surface of blood platelets, and is an important regulator in blood clotting. As this receptor is involved in platelet aggregation, and is a potential target for the treatment of thromboembolisms and other clotting disorders. Nowadays, pharmaceutical industry has developed two major drug classes:Thienopyridines series, containing Clopidogrel, Prasugrel and Ticlopidine. The other is nucleotide/nucleoside analogs, which contains Cangrelor, Elinogrel and Ticagrelor.Ticagrelor was approved by the US Food and Drug Administration on July20,2011for treating of acute coronary syndrome. Like the thienopyridines prasugrel, clopidogrel and ticlopidine, ticagrelor blocks adenosine diphosphate (ADP) receptors of subtype P2Y12-In contrast to the other anti-platelet drugs, ticagrelor has a binding site different from ADP. This binding format makes it an allosteric antagonist, and the blockage is reversible. Moreover, the drug does not need hepatic activation, which might work better for patients with genetic variants regarding the enzyme CYP2C19.In this dissertation, a series of me-too drugs derivated from Ticagrelor were designed, synthesized and assayed. We developed a new synthetic route to access the key subunit S-1. Started from chiral amino acid, the bridge ring4was constructed via regio-selective Diels-Alder reaction. Depending on the rigid structure of the bridge, two chiral centers were created via dihydroxylation from olefin. Then after remove the chiral auxiliary group and reduction to free hydroxyl group and amine, the key intermediate contains four desired chiral centers was successfully created. Then after alkylation and reduction,S-1subunit was synthesized. The route avoids the reported highly expensive starting material though it takes some steps longer.After S-1was prepared in large scale, novel P2Y12inhibitors were fully assembeled using a novel route. Meanwhile, we also established a computer model for Ticagrelor and P2Y12, which is created with Homology Modeling from bovine rhodopsin crystal protein data. After investigate the binding model, the chiral cycpropal part along with the attaching difluorophenyl ring was identified for the further exploration area as the binding is not clear form the established model. The assay protocol was also created for testing very inhibitor to evaluate the anti-platelet aggregation.Thus far, all of the working templates were created and we designed four major series of analogues based on the model and also with basic medicinal chemistry concepts. After the synthesis work and the bioassays, we got some promise results such as T-37and T-47are more potent than the control Ticagrelor. Moreover, some analogues like T-17, T-19, T-25, T-34, and T-49show very similar potency as Ticagrelor. Some useful SARs were also generated as follows.1) For phenylalkylamine series, then benzyl position substituted with fluorine shows slightly less potency than Ticagrelor. The other ring-opened analogues lost most of potency. We decided inhale the further exploration this area.2) For cyclized phenylalkylamine series, all of the analogues including alkyl-aromatic additional ring or alkyl-alkyl additional ring are lose potency no matter the ring size.3) Introducing heterocycle containing Nitrogen is an interesting idea as we identified T-37, a pyridine ring containing compound, shows more potent than Ticagrelor. Also, another pyridine ring containing compound T-34has very similar potency as Ticagrelor. It’s a very encouraging result as it shows that the molecular can be improved based on our strategies. Meanwhile, some five-membered ring (T-16and T-17) and bicyclic ring (T-12) show moderate potency.4) In the alkyl amine series, we also find the six carbon straight link (T-47) has better potency than Ticagrelor. Besides, five carbon straight link (T-49), the analogue containing a cycpropal ring (T-25) and also fluoroolefin (T-19) show ideal potency. Actually, the whole series have better potency over the other series.Based on these scattered data and SARs, our work paved a practicable methods for synthesis, evaluation compounds with the aim for treating platelets aggregate. Some interesting compounds were identified with good potency and their further profile is under investigating. It’s also give chance for further modification the other part like cyclopental ring and also the propel sulfur parts in the future.