To develop PET radiotracers for imaging of Alzheimer's disease, a new carbon-11 labeled potent and selective γ-secretase modulator (GSM) has been synthesized. The reference standard tetrahydrobenzisoxazole derivative 8 and its desmethylated precursor 9 were synthesized from cyclohex-2-en-1-one and 3-hydroxy-4-nitrobenzaldehyde in eight and nine steps with 11% and 5% overall chemical yield, respectively. The radiotracer [C]8 was prepared from its corresponding precursor 9 with [C]CHOTf through O-C-methylation and isolated by RP-HPLC combined with SPE in 45-50% radiochemical yield, based on [C]CO and decay corrected to EOB. The radiochemical purity was >99%, and the molar activity (A) at EOB was 555-740 GBq/μmol.