合成路线1

Protection of 4-piperidone (I) with trityl chloride and TEA gives 1-tritylpiperidin-4-one (II), which is condensed with ethyl 2-oxoacetate (III) by means of pyrrolidine in refluxing benzene to yield 3-(ethoxycarbonylmethylene)-1-tritylpiperidin-4-one (IV). The deprotection and simultaneous reduction of compound (IV) with NaBH4 in methanol affords the 4-hydroxypiperidine derivative (V), which is condensed with 2-bromo-1-cyclopropyl-2-(2-fluorophenyl)ethanone (VI) by means of K2CO3 in DMF to provide the adduct (VII). Reaction of the OH group of (VII) with CBr4 and PPh3 in dichloromethane gives the 4-bromopiperidine derivative (VIII), which by reaction with potassium thioacetate (IX) in ethanol provides the 4-(acetylthio)piperidine derivative (X). Selective hydrolysis of compound (X) with HCl in ethanol yields the 4-sulfanylpiperidine derivative (XI), which is finally submitted to a new hydrolysis with HCl in acetic acid.