合成路线1

合成路线2

合成路线3

The regioselective reaction of cyclopentadiene (I) and sodium or commercial sodium cyclopentadienide (II) with benzyl chloromethyl ether (III) by means of the chiral catalyst (-)-diisopinocampheylborane in THF, followed by hydroxylation with H2O2/NaOH, gives (1S-trans)-2-(benzyloxymethyl)-3-cyclopenten-1-ol (IV), which is regioselectively epoxidized with tert-butyl hydroperoxide and vanadyl acetylacetonate in 2,2,4-trimethylpentane, yielding [1S-(1alpha,2alpha,3beta,5alpha)-2-(benzyloxymethyl)-6-oxabicyclo[3.1.0]hexan-3-ol (V). The protection of (V) with benzyl bromide and NaH affords the corresponding ether (VI), which is condensed with 6-O-benzylguanine (VII) by means of LiH in DMF to give the guanine derivative (VIII). The protection of the amino group of (VIII) with 4-methoxyphenyl(diphenyl)chloromethane (IX), TEA and DMAP in dichloromethane gives intermediate (X), which is oxidized at the free hydroxyl group with methylphosphonic acid, DCC and oxalic acid in DMSO or Dess Martin periodinane in dichloromethane, yielding the cyclopentanone derivative (XI). The reaction of (XI) with (i) Zn/TiCl4/CH2Br2 complex in THF/CH2Cl2, (ii) activated Zn/PbCl2/CH2I2/TiCl4 in THF/CH2Cl2 (2), (iii) Nysted reagent/TiCl4 in THF/CH2Cl2 or (iv) Tebbe reagent in toluene affords the corresponding methylene derivative (XII), which is partially deprotected with 3N HCl in hot THF, providing the dibenzylated compound (XI). Finally, this compound is treated with BCl3 in dichloromethane. (Scheme 18263401a)