Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada.
J Am Chem Soc. 2010 Feb 10;132(5):1488-9. doi: 10.1021/ja9104478.
The chinensiolides are a family of guaiane type alpha-methylene gamma-lactone natural products recently isolated from Ixeris chinensis Nakai, a plant used in Chinese folk medicine. The first enantioselective total synthesis of (+)-chinensiolide B was accomplished in 15 steps for the longest linear sequence with an overall yield of 6.7% starting from inexpensive and readily available (R)-carvone. A highly stereoselective and E/Z-selective tandem allylboration/lactonization reaction between two highly functionalized partners was exploited as a key step. The synthesis also highlights several solutions to chemoselectivity issues arising from the reactive alpha-methylene gamma-lactone. For instance, a ring-closing metathesis formed the requisite seven-membered ring in a chemoselective fashion while avoiding the reactivity of the conjugated alpha-methylene unit.
当归属倍半萜内酯是一类 recently isolated from Ixeris chinensis Nakai 的新型瓜环型α-亚甲基γ-内酯天然产物，该植物在民间医学中被使用。从廉价易得的 (R)-柠檬烯出发，以最长线性序列 15 步总收率 6.7%完成 (+)-chinensiolide B 的首次对映选择性全合成。利用两个高功能化试剂之间高度立体选择性和 E/Z 选择性的串联烯丙基硼化/内酯化反应作为关键步骤。该合成还突出了几个针对α-亚甲基γ-内酯反应性的化学选择性问题的解决方案。例如，环 closing metathesis 以化学选择性方式形成所需的七元环，同时避免共轭α-亚甲基单元的反应性。
