Derivatives of purina as inhibitors of the protein quinasa of tirosina syk.

A compound of ** formula ** in free or salt form, where X is an oxygen or sulfur atom or an NR5 group, R1 is an alkyl group with 1 to 10 carbon atoms, alkenyl with 2 to 10 carbon atoms , cycloalkyl with 3 to 10 carbon atoms, benzocycloalkyl with 3 to 10 carbon atoms, cycloalkyl with 3 to 10 carbon atoms-alkyl with 1 to 10 carbon atoms or aryl with 6 to 10 carbon atoms-alkyl with 1 to 10 10 carbon atoms, which may be optionally substituted with hydroxy, alkoxy with 1 to 10 carbon atoms, carboxy or alkoxycarbonyl with 1 to 10 carbon atoms or, when X is NR5, R1 may alternatively be a monovalent heterocyclic radical of up to 20 carbon atoms and one to four heteroatoms selected from nitrogen, oxygen and sulfur.