Abstract
Transglycosylation from acylated pyrimidine nucleoside to purines was originally developed by Miyaki, et al. To apply this method to the naturally occurring pyrimidine nucleosides having a labile sugar moiety, we studied the improvement of this reaction. As model compounds, tri-O-acetyl-3-benzoyluridine (1) and tetraacetylcytidine (2) were employed. Reaction conditions and yields were greatly improved by utilizing (1) trimethylsilyl derivatives of exo-N-acylpurines as a glycosyl acceptor, (2) trimethylsilyl trifluoromethanesulfonate as a catalyst in acetonitrile-dichloroethane. Because of the mild reaction conditions and high yield, this procedure may be regarded as a versatile method for transglycosylation, which was shown by the successful preparation of purine analogs of the polyoxin and octosyl acid nucleosides having labile amino-or anhydrosugar uronic acid.
