[0001] Suggested is a process for making acyclovir pro-drugs by esterification of 9(2-hydroxyethyoxymethyl)-guanosine (Acyclovir) with an acylation agent, which is characterised in that the reaction is conducted in the presence of a solvent which is chosen from the group of dialkyl amides.
1. A process for making acyclovir pro-drugs by esterification of 9(2-hydroxyethyoxymethyl)-guanosine (Acyclovir) with an acylation agent, characterised in that the reaction is conducted in the presence of a solvent which is chosen from the group of dialkyl amides. 2. Process according to Claim 1, characterised in that said acylation agent is a saturated or unsaturated, linear or branched monocarboxylic acid, having 1 to 22 carbon atoms, its chloride or anhydride. 3. A process according to Claim 1, characterised in that said acylation agent is a saturated or unsaturated dicarboxylic acid having 2 to 36 carbon atoms, its chloride or anhydride. 4. A process according to any of the preceding Claims 1 to 3, characterised in that said dialkylamides follow general formula (I) R<1> CO-NR<2> R<3> (I) in which R<1> CO stands for a linear or branched, saturated or unsaturated, optionally hydroxysubstituted radical having 1 to 21 carbon atoms, and R<2> and R<3> independently from each other represent alkyl radicals having 1 to 6 carbon atoms. 5. A process according to any of the preceding Claims 1 to 4, characterised in that said dialkyl amides are based on C<6> -C<10> fatty acid, C<8> -C<10> fatty acid, lactic acid or their mixtures.