Formation of an unusual dimeric compound by lead tetraacetate oxidation of a corynanthe-type indole alkaloid, mitragynine.

Lead tetraacetate oxidation of a Corynanthe-type indole alkaloid, mitragynine, produced mainly 7-acetoxyindolenine derivative (2) together with a dimeric compound (4) as a minor product. The novel structure having a bridge between the C-11' and C-7 positions in the respective indolenine parts and its formation mechanism were studied.