... Substrates of Xanthine Oxidase JWG De Meester, W. Kraus [1], and H. С van der Pias* Department of Organic Chemistry, Wageningen Agricultural ... 1109 / Heterocyclic Chem., 24, 1109 (1987). ... over a range of 8.85-8.99 ppm for 3a-d,h and 8.35-8.52 ppm for 4e,fi,j respectively, [b ...