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Unified Asymmetric Total Syntheses of (−)‐Alotaketals A–D and (−)‐Phorbaketal A
Author(s) -
Cheng Hang,
Zhang Zhihong,
Yao Hongliang,
Zhang Wei,
Yu Jingxun,
Tong Rongbiao
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201704628
Subject(s) - tricyclic , chemistry , olefin fiber , allylic rearrangement , stereochemistry , total synthesis , enantioselective synthesis , metathesis , combinatorial chemistry , organic chemistry , catalysis , polymer , polymerization
Abstract The novel tricyclic spiroketal alotane‐type sesterterpenoids showed strikingly different biological activities and potency with subtle structural alterations. Asymmetric total syntheses of the tricyclic sesterterpenoids (−)‐alotaketals A–D and (−)‐phorbaketal A were accomplished [29–31 steps from (−)‐malic acid] in a collective way for the first time. The key features of the strategy included 1) a new cascade cyclization of vinyl epoxy δ‐keto‐alcohols to forge the common tricyclic spiroketal intermediate, 2) a late‐stage allylic C−H oxidation, and 3) olefin cross‐metathesis to install the different side chains.