181769-06-2Relevant articles and documents
Total synthesis of (±)-deethylibophyllidine: Studies of a Fischer indolization route and a successful approach via a Pummerer rearrangement/thionium ion-mediated indole cyclization
Bonjoch, Josep,Catena, Juanlo,Valls, Nativitat
, p. 7106 - 7115 (1996)
The total synthesis of (±)-deethylibophyllidine is described, proceeding in eight steps from 4-(methoxyphenyl)ethylamine in 5% overall yield (Scheme 6). In terms of sequential annulation, the strategy involves the following operations: E → DE → ABDE → ABCDE (Scheme 1). The key steps in the synthesis are the stereoselective formation of octahydroindol-6-ones by acid treatment of dihydroanisole derivatives, the regioselective Fischer indolization to obtain octahydropyrrolo[3,2-c]carbazoles, and the tandem process consisting of Pummerer rearrangement upon a β-amino sulfoxide and thionium ion cyclization upon a β-indole position of a 2,3-disubstituted indole to generate the quaternary spiro center. Attempts to effect the construction of the pentacyclic framework by means of Fischer indolization of the octahydropyrrolo[3,2,1-hi]indol-6-one resulted in failure (Scheme 2).