Piperazine-2,5-dioneGLYCINE ANHYDRIDEGlycine anhydride2,5-Dioxopiperazine2,5-Diketopiperazine2,5-Piperazinedione2,5-DIKETOPIPERAZINE2,5-哌嗪二酮2,5-二酮哌嗪甘氨酸酐Glycine anhydrideDiketopiperazinepiperazine-2,5-dione2,5-dioxopiperazine2,5-Dioxopiperazine2,5-Piperazinedione2,5-Diazacyclohexane-1,4-dioneGlycine anhydridecyclo-(Gly-Gly)