1-(2-Pyrimidinyl)piperazine (1-PP, 1-PmP) is a chemical compound and piperazine derivative. It is known to act as an antagonist of the ñ<sub>2</sub>-adrenergic receptor (K<sub>i</sub> = 7.3âÂÂ40 nM) and, to a much lesser extent, as a partial agonist of the 5-HT<sub>1A</sub> receptor (K<sub>i</sub> = 414 nM; E<sub>max</sub> = 54%). It has negligible affinity for the dopamine D<sub>2</sub>, D<sub>3</sub>, and D<sub>4</sub> receptors (K<sub>i</sub> > 10,000 nM) and does not appear to have significant affinity for the ñ<sub>1</sub>-adrenergic receptors. Its crystal structure has been determined.
A number of pyrimidinylpiperazine derivatives are drugs, including:
The anxiolytics are also classified as azapirones due to the azaspirodecanedione moiety in their structures. 1-PP is a common metabolite of most or all of the listed agents. Alnespirone, binospirone, and enilospirone, despite being azapirones, are not piperazines and therefore do not metabolize to 1-PP, and while perospirone and tiospirone are piperazines, they are instead benzothiazole-substituted piperazines and do not metabolize to 1-PP either.