Halichonadins G–J, new sesquiterpenoids from a sponge Halichondria sp

Three new dimeric sesquiterpenoids, halichonadins G–I ( 1– 3), and one new eudesmane sesquiterpenoid possessing a 1-phenethyl urea moiety, halichonadin J ( 4), were isolated from a marine sponge Halichondria sp. Halichonadins G ( 1) and H ( 2) are homo-dimers of eudesmane sesquiterpenoid, linked through a methyl 2-{1-(2-amino-2-oxoethyl)ureido}acetate fragment and a 2-hydroxymalonamide fragment, respectively, while halichonadin I ( 3) is a new hetero-dimer of eudesmane sesquiterpenoid linked through a urea fragment. The structures of 1– 4 were elucidated on the basis of spectroscopic data.