AbstractThe synthesis and physico‐chemical properties of a new 7‐amino‐8H‐8‐oxo‐oxazolo[4,5‐b]‐phenoxazine ring system(8aand8b)are reported. These tetracyclic heteroaromatic rings posses an extra oxazolo ring fused to the phenoxazinone chromophore observed in actinomycin D(1b).These tetracyclic compounds(8a‐8b)possess a structure in which the orientation of the A and B rings in1bare “reversed”. Since DNA binding and the resulting specificity of the antitumor antibiotic1bis believed to depend on the spatial orientation of P(α) and P(β) relative to the functions on the B ring of1b, these new compounds represent a novel approach for investigati