7-Methylxanthine-2,4,5,6-13C4, 1,3-15N2 (with variable 15N labeling at N9)

7-Methylxanthine-2,4,5,6-13C4, 1,3-15N2 (with variable 15N labeling at N9) is the 13C and 15N labeled 7-Methylxanthine. 7-Methylxanthine, a methyl derivative of xanthine, is one of the purine components in urinary calculi.