A novel synthesis of maleic anhydride-1- and -2-13C and its subsequent conversion to labeled maleic hydrazide

Maleic anhydride-1- and 2-13C were synthesized respectively from the available aspartic acid-4- and -3-13C by way of the corresponding bromosuccinic acids and their anhydrides. The maleic anhydrides were converted into 1,2-dihydro-3,6-pyrida-zinedione-3- and -4-13C on treatment with aqueous hydrazine sulfate. Nitrogen-15 labeled 1,2-dihydro-3,6-pyridazinedione was obtained from the latter reaction using hydrazine-15N sulfate.