合成路线1

1) The cyclization of 4(S)-hydroxytetrahydrofuran-2-one (I) with the benzylideneimine derivative (II) by means of LDA gives the trans-azetidinone (III), which is separated from its cis-isomer by crystallization. The oxidation of (III) with NaIO4 in acetonitrile yields the carbaldehyde (IV), which is condensed with the silylated enol ether (V), prepared from 4'-fluoroacetophenone (VI), Li and TMSCl, to afford compound (VII). The dehydration of (VII) by means of TsOH gives the enone (VIII), which is hydrogenated and debenzylated with H2 over Pd/C in ethanol, providing the saturated ketone (IX). Finally, this compound is enantioselectively reduced with borane and the chiral catalyst (R)-1-methyl-3,3-diphenylperhydropyrrolo[1,2-c][1,3,2]oxaazaborole (CBS). 2) Alternatively, the reduction of enone (VIII) with H2 over RhCl(PPh3)3 in dichloromethane gives the benzylated saturated ketone (X), which is enantioselectively reduced with borane and CBS, yielding the benzylated alcohol (XI). Finally, this compound is debenzylated with H2 over Pd/C in ethanol.