A new fumitremorgin, 12,13-dihydroxy-fumitremorgin C, was isolated from Aspergillus fumigatus DSM 790 and its structure elucidated. It was only produced under resting cell conditions. Tremorgenic and neurotropic intoxication has been reported in humans as a result of ingestion of Aspergillus fumigatus, growing on rice and home-made 'miso' [1]. From this fungus four fumitremorgins were isolated [2]. Cole and coworkers [2] isolated the same fungus from molded silage which caused a general deterioration of cattle when fed to them. One of these mycotoxins, verruculogen, was also isolated from Penicillium verruculosum [3], P. paraherquei [4], P. janthinellum [5], P. piscarium [6], P. paxilii [7], and Aspergillus caespitosus [8]. Aspergillus fumigatus Fres. DSM 790 produces alkaloids when maintained under resting-cell conditions in Tris buffer. Extraction of the culture broth and the mycelium with ethyl acetate and chromatography of the crude product yielded two compounds. The main product was identified as verruculogen by comparison with data from the literature [8]. The other one gave slightly yellow crystals with a composition of C₂₂H₂₅N₃O₄ determined by high resolution mass spectroscopy. The ¹H NMR spectrum showed a resonance of a methoxy group and a 1,2,4-trisubstituted benzene being part of a 2,3,6-substituted indol system. Double resonance decoupling experiments led to a structure which belongs to the fumitremorgin class already isolated from this fungus. The ¹H and ¹³C NMR spectra of the alkaloid were very similar to those published for TR-2 showing only deviations in the resonances of the side chain at C-20 [9]. Resonances at 2.00 (d, J = 1 Hz, 3H), 1.66 (d, J = 1 Hz, 3H), and 5.85 (dd, J = 9.5, 1 Hz, 1H) displaying couplings with the resonance of one proton at 4.78 (dqq, J = 9.5, 1, 1 Hz) were in agreement with an isobutenyl side chain so the structure of the alkaloid is 1. The relative configuration of 3S*, 12R*, 13S* followed from similar chemical shifts of TR-2, fumitremorgin B [10], and 1 and the long range coupling between 3-H and 13-H. It is well known from the literature that the culture conditions and the medium are important for the production of fumitremorgins. The highest amounts of 1 were isolated under resting cell conditions, while fermentation with a medium containing 1% glucose, 1% universal peptone (Merck), 2% malt extract and 0.3% yeast extract gave almost no fumitremorgins. The same negative result was observed with a fermentation in a medium containing glucose and asparagine after 59 days. Kodato and coworkers [11] prepared 12,13-dihydroxy-fumitremorgin C (1) and the two trans-12,13-epimers of 1. The data they reported are in good agreement with those reported in this paper. It is interesting to note here, that compound 1 was one of the principal alkaloids with verruculogen being the most abundant. The third metabolite was detected in similar amount to 1 and which was also produced only under resting cell conditions. High resolution mass spectroscopy revealed a composition of C₂₄H₂₉N₃O₄. The ¹H NMR spectrum showed resonances of a 3-cis-hexenyl side chain. The structure of this compound is currently under investigation.