Synthesis of [4,5-³H]-Exo-3,6-epoxyhexahydrophthatic anhydride

A convenient two-step synthesis of [4,5-³H]-Exo-3,6-epoxyhexahydrophthatic anhydride ((4,5-³H)-norcantharidin) consists of furan reacting with maleic anhydride to form dehydronorcantharidin. Then addition of tritium to dehydronorcantharidin with catalyst to form [4,5-³H]-norcantharidin. The specific activity and radiochemical purity were 56 Ci/mmol and 98%, respectively.