合成路线1

The condensation of 6-chloropurine-2-amine (III) with the chiral monoacetate (II) (obtained by enzymatic desymmetrization of diacetate (I)) by means of Pd(PPh3)4 in DMSO gives the cyclopentenol derivative (IV), which is treated with dimethyl dicarbonate and DMAP in dichloromethane to yield the carbonate (V). The condensation of (V) with ethyl 2-nitroacetate (VI) by means of Pd in THF affords the adduct (VII), which is decarboxylated by means of NaCl in DMSO/water at 150 C to provide the nitromethylcyclopentene derivative (VIII). The reaction of (VIII) with tBuOK, O3 and NaBH4 in methanol gives the corresponding hydroxymethyl derivative (IX), which is finally hydrolyzed with NaOH in refluxing water to afford the target guanine as a racemic compound. Alternatively, the nitromethyl-cyclopentene derivative (VIII) can also be obtained by condensation of carbonate (V) with 2-(trimethylsilyl)ethyl 2-nitroacetate (X) by means of Pd in THF to give the adduct (XI), which is decarboxylated by means of CsF in hot acetonitrile, affording (VIII).