合成路线1

1) The reaction of the known ketoketal (I) with N-phenyltrifluoromethanesulfonimide and KHMDS in THF gives the enol triflate (II), which is condensed with VIBuSn using tetrakis(triphenylphosphine)palladium(0) as catalyst in THF, yielding the diene (III). The reaction of (III) with 9-BBN in THF affords the alcohol (IV) and, after protection with TBDMS-Cl in dichloromethane, the silyl ether (V), which is oxidized with CrO3 and DMP in dichloromethane to the enone (VI). The stereoselective reduction of (VI) with BH3/THF catalyzed with the chiral borane (VII) yields the alcohol (VIII), which is protected with TBDMS-Cl as before to give (IX). Selective deprotection of (IX) affords the primary alcohol (X), which is oxidized with oxalyl chloride in DMSO to the aldehyde (XI). The condensation of (XI) with the vinyl iodide (XII) catalyzed by NiCl2 and CrCl2 gives the allyl alcohol (XIII), which is oxidized with oxalyl chloride as before to the enone (XIV). The oxidation of (XIV) with 3-phenyl-2-(phenylsulfonyl)oxaziridine and KHMDS yields the hydroxy ketone (XV), which is further oxidized with oxalyl chloride as before to afford the unsaturated dione (XVI). The Diels-Alder condensation between (XVI) and the diene (XVII) gives compound (XVIII) or (XIX), depending on the reaction conditions. The oxidation of the primary alcohol of (XIX) with oxalyl chloride as usual yields the aldehyde (XX), which by elimination of the ketal group in acidic medium affords the tetraketonic aldehyde (XXI).