First no-carrier-added radioselenation of an adenosine-A1 receptor ligand

✍ Scribed by Till Blum; Johannes Ermert; Walter Wutz; Dirk Bier; Heinz H. Coenen

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: French
• Weight: 178 KB
• Volume: 47
• Category: Article
• ISSN: 0022-2135
• DOI: 10.1002/jlcr.829

✦ Synopsis

Abstract

The precursor synthesis and the no‐carrier‐added (n.c.a.) radiosynthesis of the adenosine‐A~1~ receptor ligand 5′‐(methyl[^75^Se]seleno)‐N^6^‐cyclopentyladenosine ([^75^Se]1) are described in this report. A method was developed starting from elemental n.c.a. selenium‐75, followed by a three‐step polymer‐supported radioselenation and deprotection which gave the radioligand with a radiochemical yield of 30%, a radiochemical purity of > 99% and a specific radioactivity of > 300 GBq/mmol (8 Ci/mmol). Preparation time was 40 min. The nonradioactive compound 5′‐(methylseleno)‐N^6^‐cyclopentyladenosine (1) was pharmacologically evaluated in vitro and showed high affinity and selectivity for the adenosine‐A~1~ receptor. These preliminary results suggest that this compound could be a useful radioligand for the noninvasive imaging of the brain adenosine‐A~1~ receptors using positron emission tomography (PET) when labelled with the positron emitter selenium‐73 (half‐life: 7.1 h). Copyright © 2004 John Wiley & Sons, Ltd.