The calyculins, unique polyketides bearing nitrogen and phosphorus functions isolated from the Japanese marine sponge Discodermia calyx, 2-5 exhibit a variety of biological activities including antitumor, smooth muscle contractile, and tumor promotion,6 which are believed to be attributable to inhibition of protein phosphatases 1 and 2A.7 Therefore, the calyculins are important research reagents in the biological sciences. Eight known calyculins, A(1)-H, which differ by a methyl group on C-32 and in the geometry of C-2,3 and C-6,7 olefins,4 display similar inhibitory activity against protein phosphatase 2A. Further examination of D. calyx led to isolation of four more calyculin derivatives. This paper deals with the isolation and structure elucidation of these new metabolites.