A novel anthracycline, komodoquinone A (1), and its aglycone, komodoquinone B (2), were isolated from the solid-state fermentation of the marine Streptomyces sp. KS3, which was isolated from marine sediment. The absolute stereostructures of 1 and 2, except for the sugar portion, were elucidated on the basis of chemical and physicochemical evidence. Komodoquinone A (1) is a unique anthracycline, in which a new amino sugar is connected to the D-ring of the anthracyclinone skeleton, and was found to induce neuronal cell differentiation in the neuroblastoma cell line, Neuro 2A.