Purine Studies. XXI. Benzyl Group Translocations in 9-Benzylxanthine Derivatives

Abstract

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 correlated with structural configurations shown to be possible by using space-filling models.