Reactions of reducing sugars with amino acids, proteins or simple amines have been thoroughly investigated. This area of research is of great interest not only in food chemistry but also in medical biochemistry. Evidence has been accumulated that nonenzymatic glycosylation is of relevance in diabetic complications and probably in age related changeslT2. In contrast, little is known concerning the interaction of reducing sugars with nucleotides3. Glucose and glucose-&phosphate were shown to react with nucleotides or DNA under physiological conditions, giving rise to spectral changes similar to those observed for nonenzymatic glycosylation products of proteins4>. The hypothesis was established that amino groups on DNA bases could also participate in the reaction with reducing sugars, thereby resulting in DNA modification and subsequent DNA damage. It was argued that glycosylation of DNA could play a role in DNA strand breaking and may contribute to some age related changes4. To the best of our knowledge products with a definite structure have not been isolated so far5. We have investigated the glucosylation of guanosine, 2’-deoxyguanosine and some simple amino pyrimidines as model compounds. When glucose and guanosine are heated in a phosphate buffered (pH 7) aqueous solution for some hours at lOO”C, the glucosyl derivative 1 is formed as the main product (Fig. 1). The new compound was assigned the structure 1 on the basis of spectroscopic data. The 13C NMR signal associated with C-l of the glucosyl residue at 81.4 ppm is consistant with an N,O-acetal structure6. The evidence for a P-glycosidic bond comes from ‘H NMR which shows a coupling constant of 8.8 Hz for H-l. Likewise the “model compounds”, 2-amino-4,6-dimethyl-pyrimidine (2) and 2-amino-6-methyl-3H-pyrimidin-Cone (31, react with