Synthesis and Isomerization of Biindolinones from Collybia peronata and Tricholoma scalpturatum

Peronatins A and B and 7,7‘-dimethoxyperonatin B, originally isolated from the damaged fruiting bodies of Collybia peronata and Tricholoma scalpturatum, have been synthesized by oxidative dimerization of 2-alkylindoles. The conversion of peronatin A to peronatin B was shown to be catalyzed by Bronsted acids in chloroform solution and inhibited by triethylamine, implicating a retro-Mannich/Mannich isomerization pathway under these conditions. Attempts to identify or trap out radical or ionic intermediates were unsuccessful.