Pteridines, IXC. Synthesis, Oxidations and Reactions of 6- and 7-Hydroxy-2-thiolumazines Selective Cytotoxicity of Carboxypeptidase-activated Methotrexate ex-Peptides

Abstract

Various 6-(10, 11) and 7-hydroxy-2-thiolumazines (8,9) have been synthesized and oxidations of the thioamide function studied . H20 2 Oxidation of 7-hydroxy-2-thiolumazine (8) in basic medium leads to pteridine-4,7- dione-2-sulfinate (12), which eliminates S02 in anhydrous acids. Oxidative desulfurization of 8 and its 8- methyl derivative 9 proceeds directly in formic acid with H20 2 and m-chloroperbenzoic acid to give 16 and 17 respectively. KMn04 oxidation forms the pteridine-4,7,dione-2-sulfonates (14, 15), which react under hydrolytic conditions to give the corresponding 2-hydroxy derivtives (18, 19) and on displacement with ammonium acetate/ammonia at elevated temperature form the pterin derivatives 20 and 21.