Penitol A (<b>1</b>), a new citrinin derivative with a rare tricyclic spiro skeleton, was isolated from a coral-derived strain of the fungus <i>Penicillium citrinum</i>. In addition, penicitols E-I (<b>2</b>-<b>6</b>), five new citrinin analogues, were coisolated. Their structures were determined by an analysis of 1D/2D NMR and HRESIMS data, statistical DP4+ analyses based on DFT-GIAO NMR calculations, quantum chemistry ECD calculations, and a single-crystal X-ray diffraction study. The structures of penicitol A (<b>7</b>) and two related synthetic intermediates were revised. Biological evaluation results revealed that penitol A (<b>1</b>) exhibited cytotoxic activity against K562 tumor cells, with an IC<sub>50</sub> value of 8.8 μM. A proposed route of formation of compounds <b>1</b>-<b>7</b> was reported.