Radiosynthesis of dimethyl-2- F-18 -(fluoromethyl)-6-methyl-4-(2-nitrophenyl)-1,4-dihydrop yridine-3,5-dicarboxylate for L-type calcium channel imaging
Dimethyl 2-(fluoromethyl)-6-methyl-4-(2-nitrophenyl)- 1,4-dihydropyridine-3,5-dicarboxylate 4a, a fluorinated nifedipine analog, has been shown to elicit significant calcium channel blocker activity using a guinea pig ileal longitudinal smooth muscle model. In order to perform biological Studies for detection of L-type calcium channel distribution, we decided to prepare the [F-18]-labeled compound, The latter compound was prepared in no-carrier-added (n.c.a.) form from dimethyl 2-(bromethyl)-6-methyl-4-(2-nitrophenyl)1,4-dihydropyridine-3,5-dicarboxylate 2 in one step at 80 degrees C in Kryptofix/K[F-18]F and acetonitrile as a solvent in 15 min. Column chromatography afforded the radiochemically pure compound in 20 min. Radiochemical purity of the F-18-nifedipine was determined by RTLC and HPLC (> 98%) and specific activity of 21-48 GBq/mu mol (EOB).