Oxidation of 5,6-Diamino-1,3-dimethyl-2,4-dioxopyrimidine by Perrhenate: the crystal structure of 1,3,6,8-Tetramethylpyrimidopteridine-2,4,5,7-tetrone

the oxidation of 5,6-diamino-1,3-dimethyl-2,4-dioxopyrimidine (h2ddd) by perrhenate (reo4-) led to the formation of 1,3-dimethylalloxan, which condenses with unoxidized h2ddd to yield the product 1,3,6,8-tetramethylpyrimidopteridine-2,4,5,7-tetrone (tppt). the structure of tppt consists of a central pyrazine ring and two terminal pyrimidine rings in cis positions. the dihedral angles between the pyrazine and pyrimidine rings are 1.08° and 1.20°.