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Published on: August 6, 2013
Synthesis and structure-affinity relationships of selective high-affinity 5-HT(4) receptor antagonists: application
Emmanuelle Dubost1, Noé Dumas, Christine Fossey
1UFR des Sciences Pharmaceutiques, Université de Caen Basse-Normandie, EA 4258 CERMN, FR CNRS 3038 INC3M, SF-4206 ICORE, Boulevard Becquerel, F-14032 Caen, France.
Abstract:
The work described herein aims at finding new potential ligands for the brain imaging of 5-HT(4) receptors (5-HT(4)Rs) using single-photon emission computed tomography (SPECT). Starting from the nonsubstituted phenanthridine compound 4a, exhibiting a K(i) value of 51 nM on the 5-HT(4)R, we explored the structure-affinity in this series. We found that substitution in position 4 of the tricycle with a fluorine atom gave the best result. Introduction of an additional nitrogen atom inside the tricyclic framework led to an increase of both the affinity and selectivity for 5-HT(4)R, suggesting the design of the antagonist 4v, exhibiting a high affinity of 0.04 nM. Several iodinated analogues were then synthesized as potential SPECT tracers. The iodinated compound 11d was able to displace the reference radioiodinated 5-HT(4)R antagonist (1-butylpiperidin-4-yl)methyl-8-amino-7-iodo[(123)I]-2,3-dihydrobenzo[b][1,4]dioxine-5-carboxylate {[(123)I]1, [(123)I]SB 207710} both in vitro and in vivo in brain. Compound 11d was radiolabeled with [(125)I]iodine, providing a potential SPECT candidate for brain imaging of 5-HT(4)R.
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