Marine sponges have proved to be a rich source of metabolites possessing novel structural features as well as interesting biological activities, as, e.g., okadaic acid and related compounds, tedanolide and the latrunculins. In the course of our search for bioactive metabolites from Japanese marine invertebrates, we encountered a sponge Discodermia calyx whose lipophilic extract showed strong activity in the starfish egg assay and in the cytotoxicity test, which led us to isolate the active constituents. The major active constituent, calyculin A, is a novel spiro ketal of an unprecedented skeleton bearing phosphate, oxazole, nitrile, and amide functionalities. Electronic emission from d7-d7 complexes containing metalmetal single bonds is rare; to our knowledge, the only previously reported emissions are from species with low-lying metal-to-ligand charge-transfer excited states. For most d7-d7 compounds, the lowest electronic states involve population of the do* (MJ level and are extremely short-lived, precluding perceptible electronic emission. We now report that the d7-d7 complexes Pt,(pop),X;- (pop = (HO,P),O; X = CI, Br, SCN) and Pt2(pop)4(py)22- exhibit strong red luminescence at 77 K (Figure 1; Table I).