Pyrinodemins G–I, new bis-3-alkylpyridine alkaloids from a marine sponge Amphimedon sp.

Three new bis-3-alkylpyridine alkaloids, pyrinodemins G–I (1–3), were isolated from an Okinawan marine sponge Amphimedon sp. and the structures of 1–3 were elucidated on the basis of spectroscopic data. Pyrinodemins G–I (1–3) were novel bis-3-alkylpyridine alkaloids possessing an N-methoxy amide moiety, an α,β-unsaturated 3,5-disubstituted γ-lactone moiety, and a 2,3-di-substituted acrolein at a junction of two 3-alkylpyridines, respectively. Pyrinodemins G (1) and H (2) showed cytotoxicity against P388 murine leukemia cells.