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. As the results of structure–activity relationship (SAR) study of the series, the compounds with 4-methyl-quinazoline-2-yl-methyl group at N-1 position and 2-aminoethylaminomethyl group gave better activities. Compounds H4 and H9 ...
