A facile preparation of some novel class II mesoionic xanthine acyclonucleosides

The synthesis of the first examples of Class II mesoionic xanthine acyclonucleosides is described. A series of mesoionic anhydro ‐(8‐methoxyalkyl‐5‐hydroxy‐7‐oxothiazolo[3,2‐ a ]pyrimidinium hydroxides), Class II mesoionic analogs isoconjugate with xanthine, were prepared by the thermal condensation of methoxyalkyl‐2‐aminothiazoles with substituted bis(2,4,6‐trichlorophenyl)malonic esters. The memoxyalkyl‐2‐aminothiazoles were prepared via an aromatic nucleophilic substitution reaction between 2‐bromothiazole and the appropriate methoxyalkylamine in excess. The resulting 8‐methoxyalkyl‐substituted mesoionic xanthines were demethylated using iodotrimethylsilane in acetonitrile at room temperature to afford the corresponding mesoionic anhydro ‐(8‐hydroxyalkyl‐5‐hydroxy‐7‐oxothiazolo[3,2‐ a ]pyrimidinium hydroxides) as the Class II mesoionic xanthine acyclonucleosides.