Alkaline oxidation of diastereoisomeric 4a,10a-dihydrofusarubins to norjavanicin, fusarubin, and a new antibiotic isofusarubin: nonenzymic formation of products in Fusarium solani cultures

Conversion of two diastereoisomeric 4a,10a-dihydrofusarubins, produced by Fusariumsolani, to fusarubin, norjavanicin, and a new compound, isofusarubin ((E)-6,7-dihydro-5,8-dihydroxy-2-methoxy-6-methylene-7-(2-oxopropylidene)-1,4-naphthalenedione), has been studied under a variety of culture conditions and in alkaline solution. Antibiotic and phototoxic activities of these compounds were determined and the structures of isofusarubin and of anhydroisofusarubin mono- and diacetates were elucidated by 1 H and 13 C nmr.