Isolation and structure elucidation of aza-sesquiterpenoids of protoilludane origin formed by shaken cultures of the fungus Clavicorona divaricata

Two novel sesquiterpenes of protoilludane origin, the alkaloids divaricatine C and D, have been isolated from MPGB shaken cultures of the fungus Clavicorona divaricata (Basidiomycetes). Their structures were elucidated by means of NMR studies and chemical correlations. The metabolites were weakly active against bacteria and inhibited the germination of the water cress Lepidium sativum. A possible mechanism of their formation from the protoilludane tsugicoline A (2) is suggested.

Highlights► Two aza-sesquiterpenoids of protoilludane origin were isolated from cultures of the basidiomycete Clavicorona divaricata. ► Their structure and stereochemistry were determined by NMR studies. ► A possible biogenetical pathway from tsugicoline A to divaricatines C and D is proposed.