Azumamides A–E: Histone Deacetylase Inhibitory Cyclic Tetrapeptides from the Marine Sponge Mycale izuensis

A zoom in on azumamides (1): Azumamides A–E are five new cyclic tetrapeptides isolated from the marine sponge Mycale izuensis. The azumamides display inhibitory activity toward histone deacetylase with IC50 values of 0.045–1.3 μg mL−1. Their structures were determined on the basis of spectroscopic analysis and chemical degradation.