Structure of theonellapeptolide Ie, a new tridecapeptide lactone from an okinawan marine sponge, Theonella sp. (theonellidae).

A new tridecapeptide lactone named theonellapeptolide Ie (2), isolated from an Okinawan marine sponge of Theonella sp. (Theonellidae) together with theonellapeptolide Id (1) and some other minor peptide lactones, has been determined on the basis of chemical and physicochemical evidence. A new HPLC analysis method for N-methyl amino acids has been developed to analyze the amino acid composition of theonellapeptolide Id (1) and Ie (2). Ie (2) contains one N-methyl-β-alanine and two β-alanine moieties among thirteen constituent aminoacids whereas Id (1) contains three β-alanine moieties.