Abstract
Recent publications reported high uptake of the carbon‐11 labelled 11β‐hydroxylase inhibitors (R)–[O–methyl‐^11^C]metomidate ([^11^C]MTO) and (R)–[O–ethyl‐^11^C]etomidate ([^11^C]ETO) in adrenocortical incidentalomas with excellent selectivity for positron emission tomography (PET). In our studies [^18^F]FETO, (the [^18^F]fluoroethyl ester of etomidate, (R)‐1‐(1‐phenylethyl)‐1__H__‐imidazole‐5‐carboxylic acid, 2′‐[^18^F]fluoroethyl ester), an analogue of [^11^C]MTO and [^11^C]ETO was chosen due to the suspected similarity of the pharmacokinetic and pharmacodynamic properties, and was prepared in the following two step procedure: First, [^18^F]fluoride was reacted with 2‐bromoethyl triflate using the kryptofix/acetonitrile method to yield 2–bromo‐[^18^F]fluoroethane ([^18^F]BFE). In the second step, [^18^F]BFE was reacted with the tetrabutylammonium salt of (R)‐1‐(1‐phenylethyl)‐1__H__‐imidazole‐5‐carboxylic acid to yield [^18^F]FETO, a novel inhibitor of the 11β‐hydroxylase. The proposed synthesis of [^18^F]FETO allows the production of sufficient amounts of this new PET‐tracer to serve 1–2 patients with an overall synthesis time of less than 80 min. Copyright © 2003 John Wiley & Sons, Ltd.