Duclauxamide A1 (1), a new polyketide-derived heptacyclic oligophenalenone dimer with a N-2-hydroxyethyl moiety, was isolated from Penicillium manginii YIM PH30375. Spectroscopic analysis, X-ray single crystal diffraction, and (13)C NMR DFT calculations confirmed that compound 1 and other duclauxin analogues possess the unified S configuration at C-9', which corrects a long-standing misrepresentation of duclauxins as C-9'R epimers. A plausible biosynthetic pathway for duclauxins is proposed on the basis of previous acetate labeling results for duclauxin and sclerodin.