Abstract

Radiolabelled piperidine derivatives such as [C-11] MDL 100907 and [F-18] altanserin have played an important role in diagnosing malfunction in the serotonergic neurotransmission. A variety of novel piperidine MDL 100907 derivatives, possible to label with F-18-fluorine, were synthesized to improve molecular imaging properties of [C-11] MDL 100907. Their in vitro affinities to a broad spectrum of neuroreceptors and their lipophilicities were determined and compared to the clinically used reference compounds MDL 100907 and altanserin. The novel compounds MA-1 (53) and (R)-MH.MZ (56) show K-i-values in the nanomolar range towards the 5-HT2A receptor and insignificant binding to other 5-HT receptor sub-types or receptors. Interestingly, compounds MA-1 (53), MH.MZ (55) and (R)-MH.MZ (56) provide a receptor selectivity pro. le similar to MDL 100907. These compounds could possibly be preferable antagonistic F-18-tracers for visualization of the 5-HT2A receptor status. Medium affine compounds (VK-1 (32), (51), (52), (54)) were synthesized and have K-i values between 30 and 120 nM. All promising compounds show logP values between 2 and 3, that is, within the range of those for the established radiotracers altanserin and MDL 100907. The novel compounds MA-1 (53) and (R)-MH.MZ (56) thus appear to be promising high affine and selective tracers of F-18-labelled analogues for 5-HT2A imaging with PET. (C) 2009 Elsevier Ltd. All rights reserved.