Recently we reported (1) the structure 1 for flavipucine CI2Hl5NO,, an optically active metabolite of A~pergillus 3avipes possessing antibiotic activity (2). In the course of isolating this substance, the co-occurrence of an isomeric compound in the culture filtrates was noted. Isoflavipucine (mp 166-171 "C) is apparently optically inactive, [cxID2' 0" (c 1% 95% EtOH), and its nlnr spectrum (see Table 1) is remarkably similar to that of flavipucine apart from the dis- placement of ...