合成路线1

The condensation of the cis-dibenzoyloxycyclopentene (I) with the lithium salt of 2-nitrovinyl(phenyl)sulfone (II) by means of a chiral palladium catalyst and PPh3 in THF gives the chiral isoxazoline-N oxide (III), which is deoxygenated by means of SnCl2 in acetonitrile, yielding the isoxazoline (IV). The solvolysis of (IV) with K2CO3 in methanol affords the methoxy compound (V), which is treated with Mo(CO)6 and boric acid in methanol to provide the chiral 2-hydroxy-3-cyclopentene-1-carboxylic acid methyl ester (VI). The reduction of (VI) with LiAlH4 in ether yields the hydroxymethyl derivative (VII), which is esterified with methyl chloroformate and BuLi in THF to afford the bis-carbonate (VIII). The condensation of (VIII) with 2-amino-6-chloropurine (IX) by means of a Pd catalyst in THF provides the carbocyclic purine (X), which is finally treated with NaOH in refluxing water to yield the target carbocyclic guanine.