The reaction of 4,6-dichloropyrimidin-5-amine (I) with 5-aminopentanol (I) gives 4-chloro-6-(5-hydroxypentylamino)pyrimidin-5 amine (III), which is cyclized with triethyl orthoformate (IV) yielding 6-chloro-9-(5-hydroxypentyl)purine (V). The hydrolysis of (V) with formic acid affords 9-(5-hydroxypentyl) hypoxanthine (VI), which is treated with phosgene (VII) to give 9-[5-(chlorocarbonyloxy)pentyl]hypoxanthine (VIII). Finally, this compound is condensed with arginine (IX).