The experimental antitumor drug Edatrexate, labeled with 99% C-13 at t
he 2-position of the glutamate acid group was required for C-13-magnet
ic resonance spectroscopy studies in biological media. Coupling of 2,4
-diamino-4-deoxy-10-ethyl-10-deazapteroic acid with diethyl L-2-C-13-g
lutamate as promoted by BOP reagent afforded Edatrexate (2-C-13-glu) d
iethyl ester in 60% yield following purification by column chromatogra
phy. Saponification by aqueous NaOH in 2-methoxyethanol gave the targe
t molecule in 44% yield or 26% overall.