Ene-yne tetrahydrofurans from the sponge Xestospongia muta.: Exploiting a weak CD effect for assignment of configuration

Seven new brominated ene-yne tetrahydrofurans (THFs), mutafurans A-G, were isolated from the Bahamian sponge Xestospongia muta. The absolute configuration of the natural products was assigned as (5R, 8S) by interpretation of the Cotton effect arising from weak perturbation of an ene-yne chromophore by a propargylic THF ring.