Caelestines A−D, Brominated Quinolinecarboxylic Acids from the Australian Ascidian Aplidium caelestis

Four new brominated natural products, caelestines A−D (1−4), have been isolated from the Australian ascidian Aplidium caelestis. The structures of 1−4 were determined by analysis of their NMR and MS data. This is the first report of brominated quinolinecarboxylic acids from nature. Compound 1 has been previously synthesized but not spectroscopically characterized. Compounds 1−4 were tested against three mammalian cell lines (MCF-7, NFF, and MM96L) and a panel of microbial strains and showed only minor cytotoxicity.