Crystal structure of the cytotoxic macrocyclic trichothecene Isororidin A.

The highly cytotoxic macrocyclic trichothecene Isororidin A (C 29 H 40 O 9 ) was isolated from the fungus Myrothesium verrucaria endophytic on the wild medicinal plant `Datura' (Datura stramonium L.) and was characterized by one- (1D) and two-dimensional (2D) NMR spectroscopy. The three-dimensional structure of Isororidin A has been confirmed by X-ray crystallography at 0.81 Å resolution from crystals grown in the orthorhombic space group P2 1 2 1 2 1 , with one molecule per asymmetric unit. Isororidin A is the epimer of previously described (by X-ray crystallography) Roridin A at position C-13' of the macrocyclic ring.