New perylenequinone derivatives from the endophytic fungus Alternaria tenuissima SS77

Abstract Three new natural products, 1,4,6b,7,10-pentahydroxy-1,2,6b,7,8,12b-hexahydroperylene-3,9-dione ( 1 ), 1,4,9,12a-tetrahydroxy-12-methoxy-1,2,11,12,12a,12b-hexahydroperylene-3,10-dione ( 2 ) and 1,4,9-trihydroxy-1,2-dihydroperylene-3,10-dione ( 3 ), were obtained from cultures of the endophytic fungus Alternaria tenuissima SS77. Their chemical structures were determined by combined analysis of one- and two-dimensional NMR spectra, UV and ESIHRMS data. Compound 3 is likely an intermediate in the biosynthetic pathway of some perylenequinones produced by this fungus. A new hypothesis for the biosynthesis of partially reduced perylenequinones is suggested.