215232-23-8Relevant academic research and scientific papers
Total syntheses of (±)-deethylibophyllidine using a crisscross annulation: Ring cleavage of octahydroindolo[2,3-α]quinolizines followed by tandem cyclizations of octahydroazecino[5,4-b]indoles
Bonjoch, Josep,Fernàndez, Joan-Carles,Vails, Nativitat
, p. 7338 - 7347 (2007/10/03)
The total synthesis of (±)-deethylibophyllidine (1) is described. Three different sequences provide this pentacyclic alkaloid using a common strategy involving a crisscross annulation. Key steps include (i) C/D ring cleavage of a 2-formyloctahydroindolo[2,3-a]quinolizine to obtain octahydroazecino[5,4-6]indoles, via either a chloroformate induced process or a quaternary ammonium salt formation followed by treatment with lithium, and (ii) a tandem process consisting of an intramolecular Pictet-Spengler double cyclization upon a /3-indole position of a 2,3-disubstituted indole to generate the quaternary spiro center of the pentacyclic skeleton of ibophyllidine alkaloids. Attempts to extend the procedure to the construction of the pentacyclic framework of (±)-ibophyllidine result in very low yield.
