produced by Aspergillusfonsecaeus (NRRL 67, 0 16–1), viz. 5‐hydroxy‐6,8‐dimethoxy‐2‐methyl‐4H‐naphtho[2,3‐b]pyran‐4‐one (rubrofusarin B), 2,3‐dihydro‐2,5‐dihydroxy‐6,8‐dimethoxy‐2‐mehtyl‐4H‐naphtho[2,3‐b]pyran‐4‐one (fonsecin B) and 2,3‐dihydro‐2,5,8‐trihydroxy‐6‐methoxy‐2methyl‐4H‐naptho[2,3‐b]pyran‐4‐one (fonsecin), have been determined. Assignments of the carbon resonances were carried out from chemical