The structure of 2-(3'-hydroxy-2',3'-dimethylbutan-2'-yl)pyrazolo[3,4-d]pyrimidin-4(5H)-one hydrate, a photoadduct of allopurinol with 2-propanol

CllH16N402.H2 O, Mr = 254"3, monoclinic, P21/c, a = 13.343 (13), b = 6.885 (7), c = 13"334 (13)/~, fl = 91.76 (10) °, V = 1224.4 A 3, Z = 4, Dx=1"38Mgm -3, MoKa, A=0.71069A, /z= 0"064 mm- 1, F(000) = 544, T = 293 K, final R = 0.038 for 1191 unique reflections with I> 30"(/). The structure of the title compound, which is obtained by UV-irradiation of allopurinol in aqueous 2-propanol, is described. The crystals contain one molecule of water per asymmetric unit which is involved in a network of hydrogen bonding. Introduction. Owing to its inhibition of the enzyme xanthine oxidase, the purine analogue allopurinol (1)