thiouric acid thiouric acid thiouric acid, more accurately called 6-thiouric acid, is a main inactive metabolite of the immunosuppressive drugs azathioprine, mercaptopurine and tioguanine. thiouric acid names iupac name 6-thioxo-7,9-dihydro-1h-purine-2,8(3h,6h)-dione other names 6-thiouric acid identifiers cas number 2002-60-0 y 3d model (jsmol) interactive image chebi chebi:80608 chemspider 2297400 kegg c16613 pubchem cid 3032417 unii 7f23zqp3em y inchi inchi=1s/c5h4n4o2s/c10-4-6-1-2(7-4)8-5(11)9-3(1)12/h(h4,6,7,8,9,10,11,12)key: sxhqugjstgoxmd-uhfffaoysa-n smiles c12c(c(=o)1)c(=o)c2=s properties chemical formula c5h4n4o2s molar mass 184.17 g·mol−1 except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). infobox references