合成路线1

The reduction of L-pyroglutamic acid (I) with NaBH4 gives the chiral pyrrolidinone (II), which is cyclized with benzaldehyde (III) by means of Ts-OH in refluxing toluene to yield the N,O-acetal (IV). The reaction of (IV) with isobutyl chloroformate (V) and phenylselanyl chloride by means of LiHMDS in THF affords the selenoester (VI), which is treated directly with H2O2 in dichloromethane to provide the unsaturated bicyclic lactam (VII). The diastereoselective reaction of (VII) with lithium di(4-fuorophenyl)cuprate (VIII) gives the all-trans trisubstituted pyrrolidone (IX). The reduction of the carbonyl group (IX) with BH3 in THF that also causes the cleavage of the C-O bond of the oxazolidinone yields the pyrrolidine methanol derivative (X), which is submitted to ring expansion by treatment with MsCl, DCE and TEA to afford the expected trisubstituted 3-chloropiperidine (XI). The dechlorination of (XI) by means of Bu3SnH and AIBN in refluxing toluene provides the trans-1-benzyl-4-(4-fluorophenyl)piperidine-3-carboxylic acid isobutyl ester (XII), which is reduced with LiAlH4 in THF to furnish the carbinol (XIII). The reaction of (XIII) with Ms-Cl and TEA in dichloromethane gives the corresponding mesylate (XIV), which is condensed with 1,3-benzodioxol-5-ol (XV) by means of sodium isopropoxide in refluxing isopropanol to yield the aryl ether (XVI). Finally, this compound is deprotected by hydrogenation with H2 over Pd/C in methanol to afford the target trans-piperidine derivative.