Jo. Thorell et al., PREPARATION OF [C-11] DIETHYL OXALATE AND [C-11] OXALIC-ACID AND DEMONSTRATION OF THEIR USE IN THE SYNTHESIS OF [C-11] 2,3-DIHYDROXYQUINOXALINE, Journal of labelled compounds & radiopharmaceuticals, 33(11), 1993, pp. 995-1005
A method for the production of two new carbon-11 labelled difunctional
radiolabelling precursors, [C-11]diethyl oxalate, 2, and [C-11]oxalic
acid, 3. is described. Methyl chloroformate was reacted with no-carri
er-added [C-11]cyanide to generate the intermediate nitrile, methyl [C
-11]cyanoformate. Alcoholysis with HCl in ethanol generated 2, which c
ould subsequently be converted to 3 with aqueous acid. The total time
of preparation from end-of-trapping of [C-11]cyanide was 6-7 min using
combined microwave and thermal treatment or, by exclusively thermal t
reatment, 15 and 20 min for 2 and 3, respectively. The radiochemical c
onversion of [C-11]cyanide to 2 and 3 was approximately 80% and approx
imately 70%, respectively. Both 2 and 3 were used in a model reaction
with 1,2-phenylenediamine to synthesize the heterocyclic compound, 2,3
-dihydroxyquinoxaline, a basic structural unit in antagonists for the
excitatory amino acid receptor system.