Pergamon 0040-4039(95)02069-1 Tetrahedron Letters, Vol. 37, No. 1, pp. 9-12, 1996 Copyright © 1995 Elsevier Science Lid Printed in Great Britain. All rights reserved 0040-4039/96 $15.00 + 0.00 Synthesis of 8-Oxo-7,8-Dihydro-6-O-Methyl-2'-Deoxyguanosine and its use as a Probe to Study DNA-Base Excision by MutY Enzyme Chamakura V. Varaprasad, Nickolai Bulychev, Arthur P. Grollman and Francis Johnson* Department of Pharmacological Sciences, School of Medicine, Health Sciences Center State University of New York at Stony Brook, Stony Brook NY 11794-8651 Abstract: A 23mer oligomer containing 8-oxo-7,8-dihydro-6-O-methyl-2'-deoxyguanosine (1) has been synthesized from 2'-deoxyguanosine. The activity o1 MutY protein toward this and a related oligomer containing 8-methoxy-dG has been studied. Oxidative stress to DNA has emerged as one of the most important events that leads to a number of human diseases including cancer. It is known that DNA is constantly under attack by reactive oxygen species generated during normal cell metabolism. Cellular defense mechanisms against such damage include antioxidants such as uric acid, ascorbic acid and B-carotene and a number of enzymes including superoxide dismutase, catalase and glutathione peroxidase. Despite these defenses, damage still occurs and is characterized by a number of oxidized pyrimidine and purine bases of which 8-oxo-7,8-dihydro-2'- deoxyguanosine 21(8-oxo-dG) has emerged as one of the most significant. An important mechanism of repair of such potentially mutagenic lesions is the base - excision pathway. In E. Coli for example the damaged base 2 is efficiently repaired by a triad of proteins derived from genes designated as mutM, mutY and mutT. The enzymatic excision of damaged bases is arguably dependent on the recognition of the oxidative lesions and the binding efficiency of the specific enzymes to the DNA. In a previous paper 2 we have outlined a mechanism O°e H2N H2N N O N O .o- ow I I OH OH 1 2 by which MutM protein effects base excision in the case of 8-oxo-dG. In continuing studies on these enzymes we have synthesized the title compound and incorporated it into a pyrimidine rich oligomer [5'- CTCTCCCTTCXCTCCTTTCCTCT- 3', (!); where X = 8-oxo-7,8-dihydro-6-O-methyl-2'-deoxyguanosine (1)] with the objective a) of examining the mechanism by which MutY protein effects glycosidic bond cleavage of the normal base (dA), in the mismatch pair dA:8-oxo-dG, and b) to understand the enzymatic recognition aspects of this type of damage. This letter describes the details of the synthesis of the above