Sufentanil, a potent anilidopiperidine analgesic, was synthesized from a si
mple thiophenylethylamine via six step sequence. The key parts of this synt
hesis involved an efficient construction of thiophenylethylpiperidone by am
inomethano desilylation-cyclization followed by Swern oxidation and a direc
t regioselective N-nucleophilic spiral epoxide cleavage with aniline promot
ed by Lewis acids.