The condensation of the protected 3,5-difluoroaniline (I) with 1-benzyl-4-piperidone (II) by means of BuLi in THF gives 4-(1-benzyl-4-hydroxypiperidin-4-yl)-3,5-difluoroaniline (III), which is dehydrated with refluxing conc. HCl to yield the tetrahydropyridine (IV). The reaction of (IV) with benzyl chloroformate in acetone/water affords the carbamate (V), which is cyclized with (R)-glycidyl butyrate (VI) by means of BuLi in THF to provide the oxazolidinone (VII). The condensation of (VII) with isoxazol-3-ol (VIII) by means of PPh3 and DIAD in THF gives the expected ether adduct (IX), which is debenzylated by reaction with 1-chloroethyl chloroformate in dichloromethane, yielding the free tetrahydropyridine derivative (X). The condensation of (X) with (S)-2,3-O-isopropylideneglyceric acid (XI) by means of DEC or DCC and TEA in dichloromethane affords the corresponding acyl tetrahydropyridine (XII), which is finally deprotected with HCl in THF to provide the target dihydroxy compound.

The condensation of the protected 3,5-difluoroaniline (I) with 1-benzyl-4-piperidone (II) by means of BuLi in THF gives 4-(1-benzyl-4-hydroxypiperidin-4-yl)-3,5-difluoroaniline (III), which is dehydrated with refluxing conc. HCl to yield the tetrahydropyridine (IV). The reaction of (IV) with benzyl chloroformate in acetone/water affords the carbamate (V), which is cyclized with (R)-glycidyl butyrate (VI) by means of BuLi in THF to provide the oxazolidinone (VII). The condensation of (VII) with isoxazol-3-ol (VIII) by means of PPh3 and DIAD in THF gives the expected ether adduct (IX), which is debenzylated by reaction with 1-chloroethyl chloroformate in dichloromethane, yielding the free tetrahydropyridine derivative (X). The condensation of (X) with (S)-2,3-O-isopropylideneglyceric acid (XI) by means of DEC or DCC and TEA in dichloromethane affords the corresponding acyl tetrahydropyridine (XII), which is finally deprotected with HCl in THF to provide the target dihydroxy compound.