Syntheses and specific activity determinations of no-carrier-added (NCA) F-18-labeled butyrophenone neuroleptics--benperidol, haloperidol, spiroperidol, and pipamperone.

A general method for the syntheses of no-carrier-added (NCA) 18F-labeled butyrophenone neuroleptics--benperidol, haloperidol, spiroperidol, and pipamperone is described. These 18F-labeled neuroleptic drugs are synthesized by a multistep synthesis in an overall radiochemical yield of 10-20% at end of bombardment (EOB) in a synthesis time of 90 min from EOB. The sequence involves the synthesis of NCA p-[18F]fluorobenzonitrile from NCA [18F]-fluoride and p-nitrobenzonitrile using the rapidly converted to gamma-chloro-p-[18F]fluorobutyrophenone which is alkylated with appropriate amines to give NCA 18F-labeled benperidol, haloperidol, spiroperidol, and pipamperone. The final product is purified by preparative high performance liquid chromatography (HPLC). The 18F solution used in the synthesis as determined by ion chromatography contains 15.3 +/- 9.0 nmol of stable fluoride. The specific activities of the resulting butyrophenone neuroleptics were determined to be 3 Ci/mumol (at EOB) (range 1-6 Ci/mumol) as determined by radioreceptor assay and HPLC assay.