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.

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A new spirotetronate-class polyketide, maklamicin (1), was isolated from the culture extract of an endophytic actinomycete of the genus Micromonospora. The structure and relative configuration of 1 were elucidated by interpretation of NMR and other spectroscopic data, and the absolute configuration was determined using the modified Mosher method. Maklamicin (1) showed strong to modest antimicrobial activity against Gram-positive bacteria.

Enigmazole A (1), a novel phosphate-containing macrolide, was isolated from a Papua New Guinea collection of the marine sponge Cinachyrella enigmatica. The structure of 1, including the absolute stereochemistry at all eight chiral centers, was determined by a combination of spectroscopic analyses and a series of microscale chemical derivatization studies. Compound 1 is comprised of an 18-membered phosphomacrolide that contains an embedded exomethylene-substituted tetrahydropyran ring and an acyclic portion that spans an embedded oxazole moiety. Two additional analogues, 15-O-methylenigmazole A and 13-hydroxy-15-O-methylenigmazole A, were also isolated and assigned. The enigmazoles are the first phosphomacrolides from a marine source and 1 exhibited significant cytotoxicity in the NCI 60-cell line antitumor screen, with a mean GI50 of 1.7 µM.