Shishijimicins A−C, Novel Enediyne Antitumor Antibiotics from the Ascidian <i>Didemnum proliferum</i>

Abstract

Three new compounds of the enediyne antibiotics, shishijimicins A-C (1-3), have been isolated from the ascidian Didemnum proliferum. They encompass a novel sugar component, which is a conjugation product of a hexose and a beta-carboline, attached to the calicheamicinone aglycone. Their structures have been determined by interpretation of spectral data. Shishijimicins showed extremely potent cytotoxicity against HeLa cells with IC(50) values of 1.8-6.9 pM.