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A new pyrimidinedione derivative , 9 - acetyl - 1 , 3 , 7 - trimethyl - pyrimidinedione ( 1 ) , was isolated from the gorgonian coral Verrucella umbraculum , together with two known compounds , caffeine ( 2 ) and 1 , 3 - dimethylpyrimidine - 2 , 4 ( 1H , 3H ) - dione ( 3 ) .
 pyrimidinedione, 9 - acetyl - 1 , 3 , 7 - trimethyl - pyrimidinedione, caffeine, 1 , 3 - dimethylpyrimidine - 2 , 4 ( 1H , 3H ) - dione
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 pyrimidinedione, 9 - acetyl - 1 , 3 , 7 - trimethyl - pyrimidinedione, caffeine, 1 , 3 - dimethylpyrimidine - 2 , 4 ( 1H , 3H ) - dione