Polymer supported carbodiimide strategy for the synthesis of N-acylated derivatives of deoxy- and ribo purinenucleosides using active esters

A cost-effective synthetic strategy has been used for the selective protection of the exocyclic amino function of purine nucleosides. Instead of using the common protecting groups in their chloride or anhydride forms, the less expensive and nontoxic acidic form was chosen. The acids were first activated to an active ester form using DCC and further successfully used for N-acylation of purine nucleosides. The contamination of the N-acylated product with DCU was inconvenient and was avoided by use of polymer supported-carbodiimide that has the additional advantage of reusability.