合成路线1

The reaction of cyclopentadiene (I) with Br2 gives 1,4-dibromo-2-cyclopentene (II), which is treated with potassium acetate in tert-butanol yielding 1,4-diacetoxy-2-cyclopentene (III). The hydrolysis of (III) with KHCO3 in methanol affords 2-cyclopentene-1,4-diol (IV) as a mixture of the cis and trans isomers. The treatment of (cis/trans) (IV) or (cis) (IV) with pancreatin, vinyl acetate (V) and triethylamine gives (1R,4S)-4-acetoxy-2-cyclopenten-1-ol (VI), which is hydrogenated with H2 over RaNi in ethanol to yield the corresponding saturated (1S,3R)-3-acetoxycyclopentanol (VII). The reaction of (VII) with methanesulfonyl chloride and TEA in dichloromethane affords the corresponding mesylate (VIII), which is condensed with adenine (IX) by means of NaH in hot DMF providing the final intermediate (X). Finally, this compound is deacetylated with HCl in refluxing ethanol.