咯肼

5,5-diphenyl-1,3-diazinane-2,4,6-trione

N-carbamoyl-2,2-diphenylacetamide

2-amino-4,6-dioxo-4a,5-dihydropteridine-7-carboxylic acid

2-amino-4,7-dioxo-1,8-dihydropteridine-6-carboxylic acid