ethyl 4-(4-methylbenzoyl)piperazine-1-carboxylate

ethyl 4-(2,4-diaminoquinazolin-6-yl)sulfonylpiperazine-1-carboxylate

ethyl 4-(aminocarbamothioyl)piperazine-1-carboxylate

Ethyl 4-[2-(3-chlorophenyl)-2-oxoethyl]-1-piperazinecarboxylate

ethyl 4-[2-(3-chlorophenyl)-2-hydroxyethyl]piperazine-1-carboxylate