The biosynthesis of fungal metabolites. Part VI. Structures and biosynthesis of some minor metabolites from variant strains of Aspergillus variecolor

Abstract

New minor metabolites from variant strains of A. variecolor are shown to be (1R,2S)-8-[(2S)-2,3-dihydroxy-3-methylbutyl]-2,3-dihydro-1,11-dihydroxy-2-isopropenyl-5-methyl-(III), (1R,2S)-2,3-dihydro-1,11-dihydroxy-8-[(2S)-2-hydroxy-3-methoxy-3-methylbutyl]-2-isopropenyl-5-methyl-(IV), 1,2-trans-1-acetoxy-8-(2,3-epoxy-1-hydroxy-3-methylbutyl)-2,3-dihydro-11-hydroxy-2-isopropenyl-5-methyl-(V), 1,2-trans-1-acetoxy-8-(2,3-epoxy-1-methoxy-3-methylbutyl)-2,3-dihydro-11-hydroxy-2-isopropenyl-5-methyl-(VI), and 1,2-cis-2,3-dihydro-1,11-dihydroxy-2-isopropenyl-5-methyl-10-(3-methylbut-2-enyl)-pyrano[3,2-a]xanthen-12(1H)-one (X), 1,10-dihydroxy-6-methoxy-8-methyl-2-(3-methylbut-2-enyl)-7-(3-methylbut-2-enyloxy)-dibenz[b,e]oxepin-11(6H)-one (XVIII), and 1,12a-dihydro-6,8-dihydroxy-1-(1-hydroxy-1-methylethyl)-4-methyl-9-(2-hydroxy-3-methylbut-3-enyl)[1]benzopyrano[4,5-bc][1]benzoxepin-7(2H)-one (XXI). A biogenetic relationship is suggested which explains the co-occurrence of these compounds with other metabolites of known structures.