A DIRECTED METALATION ROUTE TO THE ZWITTERIONIC INDOLE ALKALOIDS. SYNTHESIS OF SEMPERVIRINE
A synthesis protocol involving beta-lithiation of 2-(2-pyridinyl)indoles(45) and subsequent reaction with bromoacetaldehyde leads to the indoloquinolizine (1) ring system.Application of this methodology to 2-(2-pyridinyl)indole 17, which is prepared via Taylor-Boger triazine Diels-Alder annulation chemistry, affords the zwitterionic indole alkaloid sempervirine (3).
Gribble, Gordon W.,Barden, Timothy C.,Johnson, David A.