合成路线1

The enantioselective condensation of the silylated 4-hydroxy-2-butanone (I) with the silylated enol ester (II) by means of Sn(OTf)2 and the chiral pyrrolidine (III) gives the chiral benzylated trihydroxyester (IV), which is partially dehydroxylated with thiocarbonyl diimidazole (TCDI) and tributyltin hydride in refluxing toluene to yield the protected dihydroxy ester (V). The reduction of (V) with DIBAL in dichloromethane affords the corresponding alcohol (VI), which is oxidized with oxalyl chloride and TEA in DMSO/dichloromethane to provide the aldehyde (VII). The condensation of (VII) with the enol ether (IX) and 2-methoxyaniline (VIII) by means of Yb(OTf)3 in THF/water gives the beta aminoketone (X), which is cyclized by means of HF, PPh3, CBr4 and cerium ammonium nitrate (CAN) in acetonitrile/water to yield the chiral piperidine (XI). The bromination of (XI) with Br2 and HBr in HOAc affords the bromo derivative (XII), which is treated with Boc2O to provide the N-protected piperidine (XIII). The condensation of (XIII) with quinazolin-4(3H)-one (XIV) by means of KOH gives the adduct (XV), which is finally deprotected and cyclized by treatment with refluxing 6N HCl to afford the target isofebrifugine.