Kulolide: A Cytotoxic Depsipeptide from a Cephalaspidean Mollusk, Philinopsis speciosa1

Kulolide, a cyclic depsipeptide, was isolated from a cephalaspidean mollusk, Philinopsis speciosa Pease, 1860. Kulolide is made up of five amino acid residues, one each of l -Ala, l -Pro, and N -Me- d -Val and two of l -Val, and two carboxylic acids, l -3-phenyllactic acid and the unprecedented ( R )-3-hydroxy-2,2-dimethyl-7-octynoic acid. The kulolide structure was elucidated by spectral techniques and hydrolytic reactions. Kulolide is active against L-1210 leukemia cells and P388 murine leukemia cells at IC 50 values of 0.7 and 2.1 μg/mL, respectively. Kulolide caused morphological change against rat 3Y1 fibroblast cells at the concentration of 50 μM.