Formal synthesis of aspidosperma alkaloids via the intramolecular [3 + 2] cycloaddition of 2-azapentdienyllithiums.
[reaction: see text] A formal synthesis of the Aspidosperma alkaloids aspidospermidine, aspidospermine, and quebrachamine is reported through an efficient preparation of Stork's penultimate intermediate. The key step of the sequence involved an intramolecular [3 + 2] cycloaddition of the 2-azapentadienyllithium 21 formed in situ from the corresponding imine 1, which after N-alkylation of the resulting cycloadduct provided 2 in excellent yield. The synthesis represents a new disconnection of the classical tricyclic ketone used for appendage of the requisite indole.
Pearson
William H
WH
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA. wpearson@berryassoc.com
Aponick
Aaron
A
D030009:Aspidosperma / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D026121:Indole Alkaloids / Q000138:chemical synthesis*; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D011804:Quinolines / Q000138:chemical synthesis*
D026121:Indole Alkaloids; D011804:Quinolines; C409672:aspidospermidine; C091897:quebrachamine; D008094:Lithium; C091896:aspidospermine