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Clinical data
Other namesR-47456; R-50656
  • 3-[2-[4-(4-Fluorobenzoyl)piperidin-1-yl]ethyl]-2-methylpyrido[1,2-a]pyrimidin-4-one
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.071.081 Edit this at Wikidata
Chemical and physical data
Molar mass393.462 g·mol−1
3D model (JSmol)
  • CC1=C(C(=O)N2C=CC=CC2=N1)CCN3CCC(CC3)C(=O)C4=CC=C(C=C4)F
  • InChI=1S/C23H24FN3O2/c1-16-20(23(29)27-12-3-2-4-21(27)25-16)11-15-26-13-9-18(10-14-26)22(28)17-5-7-19(24)8-6-17/h2-8,12,18H,9-11,13-15H2,1H3

Pirenperone (INN, USAN, BAN; developmental code names R-47456, R-50656) is a serotonin receptor antagonist described as an antipsychotic and tranquilizer which was never marketed.[1][2] It is a relatively selective antagonist of the serotonin 5-HT2 receptors and has been used in scientific research to study the serotonin system.[2][3] In the 1980s, the drug was found to block the effects of the lysergic acid diethylamide (LSD) in animals, and along with ketanserin, led to the elucidation of the 5-HT2A receptor as the biological mediator of the effects of serotonergic psychedelics.[4]


The sidechain is formed from the cyclization of 2-aminopyridine with 2-Acetylbutyrolactone (2) in PPA gave 3-(2-hydroxyethyl)-2-methylpyrido[1,2-a]pyrimidin-4-one [41078-67-5] (3). Halogenation replaces the hydroxy with the chloride leaving group. Many syntheses do both steps in one-pot with phosphorus oxychloride.

The 4-(4-Fluorobenzoyl)Piperidine [56346-57-7] has 12 known named uses.

Patent (Ex XIX):[5]

The alkylation between 3-(2-chloroethyl)-2-methylpyrido[1,2-a]pyrimidin-4-one [41078-70-0] (1) and 4-(4-fluorobenzoyl)piperidine hydrochloride [25519-78-2] (2) afforded pirenperone (3).

See also[edit]


  1. ^ J. Elks (14 November 2014). The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies. Springer. pp. 994–. ISBN 978-1-4757-2085-3.
  2. ^ a b I.K. Morton; Judith M. Hall (31 October 1999). Concise Dictionary of Pharmacological Agents: Properties and Synonyms. Springer Science & Business Media. pp. 223–. ISBN 978-0-7514-0499-9.
  3. ^ Francis C. Colpaert; Robert Balster (6 December 2012). Transduction Mechanisms of Drug Stimuli. Springer Science & Business Media. pp. 29–. ISBN 978-3-642-73223-2.
  4. ^ Nichols DE (2016). "Psychedelics". Pharmacol. Rev. 68 (2): 264–355. doi:10.1124/pr.115.011478. PMC 4813425. PMID 26841800.
  5. ^ EP0037265 idem Ludo E. J. Kennis, Josephus C. Mertens; U.S. Patent 4,342,870 (1982 to Janssen Pharmaceutica N.V.).