The protection of 3-bromo-1-propanol (I) with dihydropyran (DHP) and p-toluenesulfonic acid gives the tetrahydropyranyl ether (II), which is condensed with 3,4-dichlorophenylacetonitrile (III) by means of NaH in THF yielding the pentanenitrile (IV). The condensation of (IV) with ethyl 3-bromopropionate (V) by means of potassium hexamethyldisylazide (KHMDS) in THF affords the heptanoate (VI), which is reductocyclized with H2 over RaNi in ethanol/aq. NH4OH affording the piperidone (VII). The reduction of (VII) by means of LiAlH4 in THF gives the piperidine (VIII), which is deprotected with HCl in ethyl ether yielding the racemic propanol (IX). The optical resolution of (IX) by means of (+)-camphorsulfonic acid in isopropanol affords the desired enantiomer (X), which is acylated with benzoyl chloride (XI) and DIEA in dichloromethane providing the benzoylpiperidine (XII). The reaction of (XII) with methanesulfonyl chloride and triethylamine gives the mesylate (XIII), which is treated with KI in refluxing acetone to yield the 3-iodopropyl derivative (XIV). Finally, (XIV) is condensed with 4-hydroxy-4-phenylpiperidine (XV) by means of KHCO3 in hot acetonitrile. The intermediate 4-hydroxy-4-phenylpiperidine (XV) has been obtained as follows: The reaction of 1-benzyl-4-piperidone (XVI) with phenyllithium in THF gives 1-benzyl-4-hydroxy-4-phenylpiperidine (XVII), which is then debenzy-lated by hydrogenation with H2.

The protection of 3-bromo-1-propanol (I) with dihydropyran (DHP) and p-toluenesulfonic acid gives the tetrahydropyranyl ether (II), which is condensed with 3,4-dichlorophenylacetonitrile (III) by means of NaH in THF yielding the pentanenitrile (IV). The condensation of (IV) with ethyl 3-bromopropionate (V) by means of potassium hexamethyldisylazide (KHMDS) in THF affords the heptanoate (VI), which is reductocyclized with H2 over RaNi in ethanol/aq. NH4OH affording the piperidone (VII). The reduction of (VII) by means of LiAlH4 in THF gives the piperidine (VIII), which is deprotected with HCl in ethyl ether yielding the racemic propanol (IX). The optical resolution of (IX) by means of (+)-camphorsulfonic acid in isopropanol affords the desired enantiomer (X), which is acylated with benzoyl chloride (XI) and DIEA in dichloromethane providing the benzoylpiperidine (XII). The reaction of (XII) with methanesulfonyl chloride and triethylamine gives the mesylate (XIII), which is treated with KI in refluxing acetone to yield the 3-iodopropyl derivative (XIV). Finally, (XIV) is condensed with 4-hydroxy-4-phenylpiperidine (XV) by means of KHCO3 in hot acetonitrile. The intermediate 4-hydroxy-4-phenylpiperidine (XV) has been obtained as follows: The reaction of 1-benzyl-4-piperidone (XVI) with phenyllithium in THF gives 1-benzyl-4-hydroxy-4-phenylpiperidine (XVII), which is then debenzy-lated by hydrogenation with H2.