1,4-Dicarbethoxy piperazine 1,4-Piperazinedicarboxylic acid, diethyl ester 4-23-00-00254 (Beilstein Handbook Reference) 5470-28-0 AI3-17493 BRN 0216109 Diethyl piperazine-1,4-dicarboxylate EINECS 226-801-7 NSC 26298