diethyl 2-[[4-(3-ethoxy-2-ethoxycarbonyl-2-formamido-3-oxopropyl)piperazin-1-yl]methyl]-2-formamidopropanedioate

diethyl 2-[(3,5-ditert-butyl-4-hydroxyphenyl)methyl]-2-formamidopropanedioate

diethyl 2-formamido-2-[(4-nitrophenyl)methyl]propanedioate

diethyl 2-formamido-2-(1H-indol-3-ylmethyl)propanedioate