4-Nitrocinnamic acid (I) was activated as the succinimidyl ester (II) upon treatment with N-hydroxysuccinimide (NHS) and dicyclohexylcarbodiimide (DCC). Subsequent coupling of (II) with L-glutamine (III) afforded the N-acyl glutamine (IV). A second reaction of (IV) with NHS and DCC produced the active ester (V). Finally, thermal cyclization of (V), with concomitant racemization, led to the desired 2,6-piperidinedione.