合成路线1

The epoxidation of 3-cyclopentene-1-carboxylic acid methyl ester (I) with MCPBA in cyclohexane gives the trans-epoxide (II) along with some cis-isomer that is separated by chromatography. The reduction of the ester group of (II) with LiAlH4 in ether yields the corresponding trans-carbinol (III), which is silylated with Tbdms-Cl and imidazole to afford the silyl ether (IV). The reaction of the epoxide (IV) with the chiral lithium pyrrolidide (V) in benzene provides the (1S,3S)(trans) 3-(tertbutyldimethylsilyloxy)-4-cyclopenten-1-ol (VI). The condensation of (VI) with 2-amino-6-chloropurine by means of diethyl azodicarboxylate (DEAD) and PPh3 in dioxane gives the carbocyclic purine derivative (VIII), which is desilylated by means of TBAF in THF to the chloropurine (IX). Finally, this compound is hydrolyzed with refluxing aqueous NaOH to yield the target carbocyclic guanine.