Three new marine natural products, dysinosins B-D (1-3), were isolated from the sponge Lamellodysidea chlorea and their structures determined by 1D and 2D NMR spectroscopy. These compounds are inhibitors of the blood coagulation cascade serine proteases factor VIIa and thrombin. These analogues, dysinosins B-D (1-3), allowed identification of two structural motifs within the structures that contribute to binding to the proteases, factor VIIa and thrombin.