PURINE STUDIES .21. BENZYL GROUP TRANSLOCATIONS IN 9-BENZYLXANTHINE DERIVATIVES

Transformation of 9-benzylxanthines into the 7-benzyl isomers occurs when these purines are heated in the presence of hydrobromic acid or benzyl bromide in an aprotic solvent. Although 9-benzyl derivatives of xanthine, 1-methyl- and 1, 3-dimethyl-xanthine have been successfully isomerized in this way the reaction has not been possible with 9-benzyl-3-methylxanthine due to failure to prepare this purine. Steric effects arising from the proximity of the 3-methyl group to the 9-benzyl group have been examined by 1H n.m.r and the resulting data corrclated with structural configurations shown to be possible by using space-filling models. © 1979, CSIRO. All rights reserved.