Total Synthesis of Amphidinolide Y by Formation of Trisubstituted (E)-Double Bond via Ring-Closing Metathesis of Densely Functionalized Alkenes
摘要:
Amphidinolide Y, a 17-membered cytotoxic macrolide isolated from marine dinoflagellates, has been synthesized via ring-closing metathesis to assemble the congested trisubstituted (E)-double bond. The seco precursor was prepared from readily available chiral synthons with the tetrahydrofuran ring formed via 5-endo epoxide ring-opening cyclization. It was found that the C6-keto seco substrate showed higher reactivity toward Grubbs' second generation catalyst while Schrock's Mo catalyst was completely inactive for formation of the macrocycle.
opening reaction of the enantioenriched propargyl epoxide 16 (derived from a Sharpless epoxidation) with a Grignard reagent. Allenol 17 was then cyclized with the aid of Ag(I) to give dihydrofuran 19 containing the (R)-configured tetrasubstituted sp3 chiral center at C.19, which was further elaborated into tetrahydrofuran 25 representing the common heterocyclic motif of 1 and 2. The aliphatic chain of amphidinolide
描述了细胞毒性海洋天然产物amphidinolide X (1) 和amphidinolide Y (2) 以及非天然类似物19-epi-amphidinolide X (47) 的简明总合成。这些结构上相当不寻常的次级代谢物的高度收敛路线的关键步骤包括通过铁催化的对映体富集的炔丙基环氧化物 16(源自 Sharpless 环氧化)与格氏试剂的开环反应,顺式选择性形成丙二烯醇 17 . 然后在 Ag(I) 的帮助下将 Allenol 17 环化,得到二氢呋喃 19,该二氢呋喃 19 在 C.19 处含有 (R) 构型的四取代 sp3 手性中心,其进一步细化为代表 1 和 2 的常见杂环基序的四氢呋喃 25。 amphidinolide X 的脂肪族链在 C.10 和 C 处具有反构型立体二联体。11 是通过钯催化、Et2Zn 促进的对映纯甲磺酸炔丙酯 29 加成到官能化醛 28 中产生的。