Novel probes for imaging amyloid-β: F-18 and C-11 labeling of 2-(4-aminostyryl)benzoxazole derivatives

2-(4-Methylaminostyryl)-6-(2-[¹⁸F]fluoroethoxy)benzoxazole ([¹⁸F]BF-168) was prepared and found to be a potential probe for imaging amyloid-β. The precursor, a 6-(2-tosyloxyethoxy)benzoxazole derivative, was fluorinated with [¹⁸F]KF and Kryptofix 222 in acetonitrile, and the crude product purified by semi-preparative HPLC to give [¹⁸F]BF-168. The radiochemical purity was > 95% and the maximum specific activity was 106 TBq/mmol at the end of synthesis. The synthesis time was 110 min from the end of bombardment. 2-(4-[N-methyl- ¹¹C]methylaminostyryl)-5-fluorobenzoxazole ([¹¹C]BF-145) was also prepared from 2-(4-aminostyryl)-5-fluorobenzoxazole, [ ¹¹C]MeI and 5 N NaOH in DMSO, and purified by semi-preparative HPLC. The radiochemical purity was > 95% and the specific activity was 40-70 TBq/mmol at the end of synthesis. The synthesis time was 45 min from the end of bombardment.