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J Med Chem. 1999 Jul 15;42(14):2706-15.

1-(3-Cyanobenzylpiperidin-4-yl)-5-methyl-4-phenyl-1, 3-dihydroimidazol-2-one: a selective high-affinity antagonist for the human dopamine D(4) receptor with excellent selectivity over ion channels.

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Departments of Medicinal Chemistry, Biochemistry, and Pharmacology, Merck Sharp and Dohme Research Laboratories, Neuroscience Research Centre, Terlings Park, Eastwick Road, Harlow, Essex CM20 2QR, U.K.


After the requirement of pseudocycle formation in the ureas 3 and 7 for hD(4) binding and selectivity was confirmed, structural hybridization with the known hD(4) ligand 2 led to the design and identification of the lead 4-(2-oxo-1, 3-dihydroimidazol-2-yl)piperidine 8. Optimization studies were carried out on 8 with the aim of achieving 1000-fold selectivity for hD(4) over all other receptors while retaining the good pharmacokinetic properties of the lead. After initial preparation of 8 as a minor component in a low-yielding reaction, a novel and regioselective "four-step/one-pot" procedure was developed which proved to be applicable to rapid investigation of the SAR of the 1, 3-dihydroimidazol-2-one ring. Various changes to substituents attached to the 3-, 4-, or 5-position of the 1, 3-dihydroimidazol-2-one core of 8 did not significantly improve selectivity for hD(4) over hD(2) and hD(3). Greater selectivity (>1000-fold) was ultimately achieved by meta substitution of the benzyl group of 8 with various substituents. Compounds 28, 31, and 32 all possess the required selectivity for hD(4) over the other dopamine subtypes, but only 32 has >1000-fold selectivity over all the key counterscreens we tested against. Compound 32 is an antagonist at hD(4) and has a good pharmacokinetic profile in the rat, with excellent estimated in vivo receptor occupancy, thus making it a potentially useful pharmacological tool to investigate the role of the D(4) receptor.

[Indexed for MEDLINE]

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