Unified Asymmetric Total Syntheses of (−)‐Alotaketals A–D and (−)‐Phorbaketal A

• DOI: 10.1002/anie.201704628
• Publication Date: 2017-06-02T14:48:43Z
• Authors: Hang Cheng; Zhihong Zhang; Hongliang Yao; Wei Zhang; Jingxun Yu; Rongbiao Tong
• Keywords: Tricyclic

Abstract The novel tricyclic spiroketal alotane‐type sesterterpenoids showed strikingly different biological activities and potency with subtle structural alterations. Asymmetric total syntheses of the (−)‐alotaketals A–D (−)‐phorbaketal A were accomplished [29–31 steps from (−)‐malic acid] in a collective way for first time. key features strategy included 1) new cascade cyclization vinyl epoxy δ‐keto‐alcohols to forge common intermediate, 2) late‐stage allylic C−H oxidation, 3) olefin cross‐metathesis install side chains.