Condensation of 2,6-dichloropurine (I) with benzylamine (II) in boiling butanol afforded 6-(benzylamino)-2-chloropurine (III), which was subsequently alkylated at the 9-N with isopropyl bromide (IV), yielding purine (V). The 2-chloro group was finally displaced with (R)-2-amino-1-butanol (VI) in a sealed tube at 160 C to provide the title compound.