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A Concise and Versatile Synthesis of Alkaloids from Kopsia tenuis : Total Synthesis of (±)‐Lundurine A and B
Author(s) -
Arai Shigeru,
Nakajima Masaya,
Nishida Atsushi
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201400464
Subject(s) - total synthesis , cyclopropane , stereochemistry , indoline , chemistry , stereospecificity , metathesis , ring (chemistry) , ring closing metathesis , stereoselectivity , radical cyclization , catalysis , organic chemistry , polymer , polymerization
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 SmI 2 , 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.