A General Strategy for the Synthesis of Cladiellin Diterpenes: Enantioselective Total Syntheses of 6-Acetoxycladiell-7(16),11-dien-3-ol (Deacetoxyalcyonin Acetate), Cladiell-11-ene-3,6,7-triol, Sclerophytin A, and the Initially Purported Structure of Sclerophytin A
作者:David W. C. MacMillan、Larry E. Overman、Lewis D. Pennington
DOI:10.1021/ja016351a
日期:2001.9.1
step; chemo- and stereoselective hydroxyl-directed epoxidation of 49, 72, and 90 followed by regioselective reductive opening with hydride to install the C3 tertiary hydroxyl group; and a diastereoselective Nozaki-Hiyama-Kishi cyclization of iodoaldehyde 56 to forge the oxacyclononane ring and the C6 hydroxyl stereocenter. Other key transformations include chemo- and stereoselective hydroxyl-directed
cladiellin diterpenes, 6-acetoxycladiell-7(16),11-dien-3-ol (deacetoxyalcyonin acetate, 6), cladiell-11-ene-3,6,7-triol (1), sclerophytin A 的对映选择性全合成(8) 和四环二醚 7 是通过三环烯丙醇 57 的差异加工实现的。 这些合成的核心步骤是酸促进的 α,β-不饱和醛 45、69 或 87 和环己二烯二醇 44 缩合为形成,完全立体控制,六氢异苯并呋喃核心和这些 cladiellin 二萜的五个立体中心。这些合成还具有 β、γ-不饱和醛 46、70 和 71 的立体定向光解脱甲酰化作用,以去除在 Prins-频哪醇步骤中引入的外来碳;化学和立体选择性羟基导向环氧化 49, 72, 和 90 然后用氢化物进行区域选择性还原开环以安装 C3 叔羟基;和碘醛