RESUMO
We report herein the asymmetric total synthesis of periglaucines A-C, N,O-dimethyloxostephine and oxostephabenine. The key strategies used include: 1)â a RhI -catalyzed regio- and diastereoselective Hayashi-Miyaura reaction to connect two necessary fragments; 2)â an intramolecular photoenolization/Diels-Alder (PEDA) reaction to construct the highly functionalized tricyclic core skeleton bearing a quaternary center; 3)â a bio-inspired intramolecular Michael addition and transannular acetalization to generate the aza[4.4.3]propellane and the tetrahydrofuran ring.
Assuntos
Alcaloides , Estereoisomerismo , Compostos Heterocíclicos de 4 ou mais Anéis , Reação de CicloadiçãoRESUMO
A Lewis acid promoted intramolecular Schmidt reaction of N-acylbenzotriazoles with alkyl azides was designed and realized. The benzotriazole was not only employed as an efficient activator for initiating the Schmidt rearrangement but also used as a powerful terminator for the subsequent nucleophilic trapping of the isocyanate ion and/or N-acyliminium ion from the rearrangement. Thirteen δ-azido N-acylbenzotriazoles were investigated, and the conversion afforded the desired benzotriazole-1-carboxamides and lactams with good to excellent yields.
RESUMO
The Schmidt reaction of ω-azido valeryl chlorides in the presence of an additional nucleophile was explored. The arenes, alcohols, and amines were demonstrated as the intermolecular trapping reagents for isocyanate ion and N-acyliminium ion from the Schmidt rearrangement, affording the corresponding products with moderate to excellent yields. Two 2-oxoindoles from the reaction were successfully converted into four natural alkaloids, namely, assoanine, anhydrolycorine, oxoassoanine, and anhydrolycorinone.