The alkylation of 5-amino-1H-imidazole-4-carboxamide (I) with benzyl chloride and NaOH in DMSO gives 5-amino-1-benzyl-1H-imidazole-4-carboxamide (II), which is cyclized with ethyl pentanoate (III) and EtONa in ethanol to yield 9-benzyl-2-butylpurine-6-ol (IV). The reaction of (IV) with POCl3 and diethylaniline affords the corresponding chloropurine (V), which by reaction with aqueous ammonia in n-butanol is converted into 9-benzyl-2-butyladenine (VI). The bromination of (VI) with Br2 affords the 8-bromo derivative (VII), which is finally hydrolyzed with aqueous HCl to afford the target 8-hydroxyadenine derivative.