Chagosendines A - C, New Metal Complexes of Imidazole Alkaloids from the Calcareous Sponge Leucetta chagosensis.

Chemical examination of the bright yellow sponge Leucetta chagosensis resulted in the isolation of three new imidazole-based alkaloid complexes namely chagosendines A - C (1 - 3), together with known analogues pyronaamidine, naamidine J, and naamine C. Their structures were determined on the basis of extensive spectroscopic (IR, MS, NMR, and single-crystal X-ray diffraction) analysis in association with the chemical conversion. The isolated alkaloids together with three synthesized new homodimer complexes were evaluated for the cytotoxic activities against a panel of tumor cell lines. The copper complexes of imidazole alkaloids 2 and 3, as found from nature for the first time, exerted selective and remarkable activities against the tumor cell lines K562, HepG2, and HeLa.