Halichonadins G―J, new sesquiterpenoids from a sponge Halichondria sp.

Abstract 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.