Purine derivative dihydrate, drugs containing the same as the active ingredient and intermediate in the production thereof

A compound represented by the following formula (I), or a salt thereof: ##STR1##

where X is a halogen atom or a group represented by -S-(CH₂)_n-A, -SO-(CH₂)_m-B, -SO₂-(CH₂)_m -B, -OSO₂-(CH₂)_m-B, -OCO-(CH₂)_m-B or -OPO(OR)-(CH₂)_m-B, wherein n represents an integer of 0-4, A represents an optionally substituted aromatic hydrocarbon group or an optionally substituted heterocyclic residue having 1 to 4 hetero atoms selected from an oxygen atom, sulfur atom and nitrogen atom and having 5 to 10 ring-constituent atoms, m represents an integer of 0-4, B represents an optionally substituted alkyl group, an optionally substituted aromatic hydrocarbon group or an optionally substituted heterocyclic residue having 1 to 4 hetero atoms selected from an oxygen atom, sulfur atom and nitrogen atom and having 5 to 10 ring-constituent atoms, and R represents an optionally substituted alkyl group.