Phytotoxic naphthopyranone derivatives from the coprophilous fungus Guanomyces polythrix

Reinvestigation of the fermentation broth and mycelium of the coprophilous fungus Guanomyces polythrix, grown in static conditions, led to the isolati on of several phytotoxic compounds, including two new naphthopyranone deriv atives, namely (2S, 3R)-5-hydroxy- 6,8 -dimethoxy -2,3 -dimethyl -2,3 -dihy dro-4H-naphtho [2,3 - b]-pyran-4-one and (2S, 3 R)- 5-hydroxy-6,8,10-trimet hoxy-2,3-dimethyl-2,3-dihydro-4H-naphtho[2,3-b]-pyran-4-one. The structures of the new compounds were established by spectral and chiroptical methods. In addition, the structure of 8-hydroxy-6-methyl-9-oxo-9H-xanthene-1-carbo xylic acid methyl ester was unambiguously determined by X-ray analysis. The isolates caused significant inhibition of radicle growth of two weed seedl ings (Amaranthus hypochondriacus and Echinochloa crusgalli) and interacted with both spinach and bovine brain calmodulins. (C) 2001 Elsevier Science L td. All rights reserved.