title: Improved synthesis of the A-G ring segment of brevetoxin B.
abstract: An efficient synthesis of the A-G ring segment 2, a key intermediate for the total synthesis of brevetoxin B (1), was achieved in 37 steps and 5.0% overall yield. The intramolecular allylation of the O,S-acetal 22, prepared from the ABC ring segment 15 and the FG ring segment 17, was carried out using AgOTf as a Lewis acid to give the desired compound 23, predominantly. Ring-closing metathesis of 23 with the Grubbs catalyst 12 afforded the heptacyclic ether 25. Selective hydrogenation of the E ring olefin of 25 was performed by diimide reduction to afford 2.
authors.affiliation: Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan. ikadota@mail.tains.tohoku.ac.jp
authors.forename: Isao
authors.initials: I
authors.lastname: Kadota
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nishii
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ishioka
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Takamura
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D008387:Marine Toxins / Q000138:chemical synthesis*; D015394:Molecular Structure; D035964:Oxocins / Q000138:chemical synthesis*; D000095702:Polyether Toxins
chemical_list: D008387:Marine Toxins; D035964:Oxocins; C043466:brevetoxin B; D000095702:Polyether Toxins