14338
A series of xanthine derivatives in which a methylene was inserted at position 8 of xanthine scaffold was synthesized and evaluated as inhibitors of dipeptidyl peptidase 4 ( DPP - 4 ) for the treatment of type 2 diabetes .
 Chemical: xanthine; Chemical: methylene; Chemical: xanthine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: xanthine; Chemical: methylene; Chemical: xanthine