Five new diketopiperazine alkaloids, brevicompanines D-H (3-7), together with two known analogs, allo-brevicompanine B (1) and fructigenine B (2), were isolated from a deep ocean sediment derived fungus Penicillium sp. Their structures were established by spectroscopic methods including 2D NMR and chiral HPLC analysis. Compounds 4 and 7 inhibited lipopolysaccharide (LPS)-induced nitric oxide production in BV2 microglial cells.