Stereoselective formal synthesis of pseudodistomin C

[reaction: see text] Trisubstituted benzenesulfonylmethylpiperidine 4, in which the substituents are all cis to each other, is a direct synthetic precursor of the cytotoxic marine alkaloid pseudodistomin C; it has been synthesized with total diastereoselectivities from (S)-pyroglutaminol.