Synthesis and structure-activity relationships of a new series of antiarrhythmic agents: 4,4-disubstituted hexahydro-3H-pyrido[1,2-c]pyrimidin-3-ones and related compounds

Abstract

A series of 4,4-disubstituted tetrahydro- and 4,4-disubstituted hexahydro-3H-pyrido[1,2-c]pyrimidin-3-ones (4 and 5, respectively) were prepared from 2-aryl-2-(2-piperidinyl)-4-[N,N-bis (1-methylethyl)amino] butanamides (2). Individual racemates of the piperidinyl amides 2 were converted to pure racemic diaza bicyclic compounds that were evaluated for antiarrhythmic activity in the Harris dog model and anticholinergic activity in a muscarinic receptor binding assay. Selected compounds were subsequently evaluated for hemodynamic effects in anesthetized dogs where blood pressure depression and negative inotropic activity were assessed. Of this group, 4a (R = CH3) and 5a (R = CH3) showed the most favorable pharmacological profiles; the former compound was chosen for toxicity testing over the latter due to its lack of noncompetitive inhibition of acetylcholine-induced contractions of guinea pig ileum segments. Clinical evaluation is now under way.