Improved Synthesis of the C8-C23 Segment of Aplysiatoxins via Asymmetric Dihydroxylation of the Chiral Homoallylic Alcohol.

Important intermediate 2 of the segment (3) possessing four sequential asymmetric centers (C-9-C-12) of aplysiatoxins was synthesized via dihydroxylation of 5 in only 7 steps from methyl (S)-3-hydroxy-2-methylpropionate. Another promising compound (10a) was also synthesized in only 6 steps via asymmetric dihydroxylation of chiral homoallylic alcohol 4 as the key step.