The discovery that kinamycin antitumor antibiotics possess the diazobenzo[b]fluorene (1) rather than the N-cyanobenzo[b]carbazole (2) ring system stimulated interest in their biosynthesis, mechanism of action, and chemical synthesis. Hauser and Zhou's synthetic compound 3 was found to match CpdB (reassigned as prekinamycin), leaving the structure of CpdA unresolved. We report herein that CpdA is isoprekinamycin, which possesses the diazobenzo[a]fluorene structure 4. We reevaluated the deazotization evidence for CpdA: ab initio calculations revealed the previously proposed product 7 was much less stable than tautomers 8 or 9, suggesting CpdA does not contain the benzo[b]fluorene system. HMBC analysis of CpdA diacetate uncovered partial structures, and sodium borohydride reduction of CpdA yielded a tetrahydroxy compound that was converted to tetraacetate 10. 1D and 2D NMR spectroscopy, along with isotope labeling using sodium borodeuteride, confirmed the structure of 10, which is only compatible with CpdA having structure 4. Spectroscopic comparison with synthetic benzo[a]fluorene model compounds 11 and 12 further supported this assignment. We conclude that Streptomyces murayamaensis likely has mechanisms for interconverting benzo[b]fluorenes and benzo[a]fluorenes, and biomimetic conversion studies are in progress to access fluostatin-like systems using methodologies developed for kinamycin-related compounds.