合成路线1

Alternatively, the inosine uronic acid (I) is converted to ethyl ester (II) by sequential treatment with thionyl chloride and then ethanol. Subsequent reaction with acetic anhydride in pyridine gives rise to diacetate (III). Chlorination of the inosine ring of (III) to produce (IV) is accomplished by treatment with phosphoryl chloride in the presence of tetraethylammonium chloride. Displacement of the 6-chloro group of (IV) with cyclopentylamine (V) yields amino purine (VI). Finally, aminolysis of the ester groups of (VI) with ethanolic ethylamine leads to the title compound.