The stereoselective synthesis of (−)-pericosine B, which is the antipode of the cytotoxic metabolite of the fungus Periconia byssoides OUPS-N133 separated from the sea hare, was accomplished in 9 steps in 12% total yield from (−)-quinic acid, together with the synthesis of its epimer. Every crucial step of this total synthesis, including ring opening of a β-epoxide and NaBH4reduction of an unstable