合成路线1

The reaction of protected pyrrolidone (VIII) with LHMDS and CO2 affords the corresponding pyrrolidonecarboxylic acid (IX), which is reduced at the ketonic oxygen with NaBH4 providing the hydroxyacid (X). The condensation of the previously obtained amino acid (VII) with the acid (X) by means of oxalyl chloride and triethylamine affords amide (XI), which is condensed with vinyltributylstannane (XII) by means of Pd(PPh3)4 to give the butaiene derivative (XIII). The spontaneous Diels-Alder cyclization of (XIII) yields the tricyclic compound (XIV), which is oxidized with CrO3 to the dione (XV). The deprotection of the hydroxyl groups of (XV), their reaction with oxalyl chloride and with methylenetriphenylphosphorane provides compound (XVI) with two terminal reactive double bonds. The reduction of (XVI) with DIBAL, followed by oxidation with Dess Martin periodinane (DMP) affords the corresponding aldehyde (XVII).