Acetonide (VII) was prepared by treatment of 2-chloroadenosine (VI) with 2,2-dimethoxypropane and camphorsulfonic acid. Subsequent oxidation of (VII) with KMnO4 under basic conditions produced the carboxylic acid (VIII). After activation of (VIII) as the corresponding acid chloride (IX), reaction with ethylamine afforded amide (X). Condensation of amine (V) with the chloroadenosine derivative (X) at 130 C furnished the diaminopurine adduct (XI). Finally, simultaneous cleavage of the tert-butyl ester and acetonide groups of (XI) upon acidic treatment provided the title compound
The intermediate amine (V) was prepared via a Heck reaction between p-bromophenylacetonitrile (I) and tert-butyl acrylate (II) to afford the p-(cyanomethyl)cinnamate (III) . Catalytic double bond hydrogenation in (III) provided the saturated cyano ester (IV), which was then reduced to amine (V) by using NaBH4 in the presence of CoCl2. Alternatively, simultaneous double bond and cyano group reduction was accomplished by hydrogenation of (III) in the presence of Pd/C and HCl.