New asymmetric routes to ajmaline and suaveoline indole alkaloids

The tetracyclic advanced intermediates 6, 8 and 9 obtained from L-tryptopha n via a cis-selective Pictet-Spengler reaction and a Dieckmann-Thorpe cycli sation are used in a range of new approaches to polycyclic monoterpenoid in dole alkaloids such as ajmaline and suaveoline. Structural modifications de signed to facilitate a key intermolecular addition to C15 (ajmaline numberi ng) are described, followed by two intramolecular routes based on the addit ion of a suitable carbon fragment to a remote nitrogen atom prior to bond f ormation at C15.