title: A concise and versatile synthesis of alkaloids from Kopsia tenuis: total synthesis of (±)-lundurine A and B.
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.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 2608675 (Japan).
authors.forename: Shigeru
authors.initials: S
authors.lastname: Arai
authors.forename: Masaya
authors.initials: M
authors.lastname: Nakajima
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nishida
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D029062:Apocynaceae / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D003500:Cyclization; D007211:Indoles / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D007211:Indoles; D011083:Polycyclic Compounds; C000597197:lundurine A; C000590471:lundurine B; D010165:Palladium; C057812:indoline; D012428:Ruthenium
keywords: cyclopropanes; natural products; nitrogen heterocycles; samarium; total synthesis