Structure-activity relationships of pyrroloquinazolines as thrombin receptor antagonists.

A series of pyrroloquinazolines has been discovered that represent novel small molecule inhibitors of the intramolecular ligand of the thrombin receptor. Analogs were prepared to study the structure-activity relationships of substitution at the N 1, N3, and N7 positions of the heterocycle. Compounds 4e and 4f have been identified with IC50's of 56 and 52 nM, respectively.

2-Azetidinone cholesterol absorption inhibitors: structure-activity relationships on the heterocyclic nucleus.

A series of azetidinone cholesterol absorption inhibitors related to SCH 48461 ((-)-6) has been prepared, and compounds were evaluated for their ability to inhibit hepatic cholesteryl ester formation in a cholesterol-fed hamster model. Although originally designed as acyl CoA: cholesterol acyltransferase (ACAT) inhibitors, comparison of in vivo potency with in vitro activity in a microsomal ACAT assay indicates no correlation between activity in these two models. The molecular mechanism by which these compounds inhibit cholesterol absorption is unknown. Despite this limitation, examination of the in vivo activity of a range of compounds has revealed clear structure-activity relationships consistent with a well-defined molecular target. The details of these structure-activity relationships and their implications on the nature of the putative pharmacophore are discussed.

Antiulcer agents. 2. Gastric antisecretory, cytoprotective, and metabolic properties of substituted imidazo[1,2-a]pyridines and analogues.

The search for a successor to 3-(cyanomethyl)-2-methyl-8-(phenylmethoxy)imidazo[1,2-a]pyridine, Sch 28080 (27), a compound that exhibits gastric antisecretory and cytoprotective properties and has undergone clinical evaluation as an antiulcer agent, has culminated in the identification of four related compounds that exhibit pharmacologic profiles similar to that of 27. In three of these potential successors an amino group functions as a surrogate for the 3-cyanomethyl substituent of the prototype. The present work concerns, in addition to an evaluation of the structure-activity relationships of a series of analogues of 27, preliminary studies of the pharmacodynamics and metabolism of 27, performed with the aid of cyano carbon labeled versions of the drug (13C labeled; 28; 14C labeled, 29). These studies have shown that 27 is well-absorbed and extensively metabolized and that the major metabolite of 27 is the thiocyanate anion. A similar study performed on 3-amino-2-methyl-8-(phenylmethoxy)imidazo[1,2-a]pyridine, labeled at the 3-position with carbon-13 (41) or carbon-14 (42), revealed that this compound, which has an antisecretory/cytoprotective profile comparable to that of 27, is also metabolized to thiocyanate anion, although this must occur via a different mechanism. The chemistry section includes a discussion of the potential sites of protonation of the pharmacologically similar 3-amino analogue 40 and the structurally related imidazo[1,2-a]pyrazine 67. Predictions based on charge density and protonation product stabilities are presented. That N1 is the site of protonation in these analogues has been definitively demonstrated by X-ray crystal structure analysis, which also unequivocally established the assigned imidazo[1,2-a]pyrazine ring structure.

Antiinflammatory activity of substituted 6-hydroxypyrimido[2,1-f]purine-2,4,8(1H,3H,9H)-triones. Atypical nonsteroidal antiinflammatory agents.

A novel class of antiinflammatory drugs, which are substituted derivatives of the fused tricyclic system 6-hydroxypyrimido[2,1-f]purine-2,4,8(1H,3H,9H)-trione, is described. Synthetic procedures and structure determination with the assistance of X-ray crystallography are discussed. Semiempirical molecular orbital calculations are used to investigate the relative stability of the possible isomers and tautomers of the title compounds. A biological profile of the class, and of several of the more potent analogues, in several antiinflammatory models, including the adjuvant-induced arthritis and the collagen II models, is defined. Several members of the class are shown to possess extremely low ulcerogenic effects in spite of exhibiting cyclooxygenase inhibition. A preliminary bioavailability study of two of the lead structures is presented. The compounds 6-72 appear to constitute a class of drugs that shows interesting potential antiarthritic activity and also exhibits an activity profile different from that of the standard classical NSAI drugs, as determined by a comparison of the profile of this class of drug with that of several standard agents. Certain findings from toxicological studies have precluded the further development of compounds within this group, although related structural types are being investigated.

Antiulcer agents. 1. Gastric antisecretory and cytoprotective properties of substituted imidazo[1,2-a]pyridines.

A novel class of antiulcer agents, the substituted imidazo[1,2-a]pyridines, is described. The present compounds are not histamine (H2) receptor antagonists nor are they prostaglandin analogues, yet they exhibit both gastric antisecretory and cytoprotective properties. The mechanism of gastric antisecretory activity may involve inhibition of the H+/K+-ATPase enzyme. Structure-activity studies led to the identification of 3-(cyanomethyl)-2-methyl-8-(phenylmethoxy)imidazo[1,2-a]pyridine, SCH 28080 (27), which was selected for further development and clinical evaluation.