A Concise and Versatile Synthesis of Alkaloids from Kopsia tenuis: Total Synthesis of (±)‐Lundurine A and B |
| |
Authors: | Prof Shigeru Arai Masaya Nakajima Prof Atsushi Nishida |
| |
Institution: | Graduate School of Pharmaceutical Sciences, Chiba University, 1‐8‐1 Inohana, Chuo‐ku, Chiba 2608675 (Japan) |
| |
Abstract: | A total synthesis of (±)‐lundurines A and B is described. These natural products have a unique hexacyclic skeleton which includes a cyclopropane‐fused indoline. A stereospecific construction of the pentasubstituted cyclopropane core was achieved, by radical cyclization using SmI2, with perfect stereoselectivity. Cyclizations to give seven‐ and five‐membered heterocycles, under palladium and ruthenium catalysis, respectively, accomplished the total syntheses. The late‐stage construction of the F ring by ring‐closing metathesis enabled access to the title compounds from a spiroindoline intermediate which is a common structure of other kopsia alkaloids. |
| |
Keywords: | cyclopropanes natural products nitrogen heterocycles samarium total synthesis |
|
|