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

Four new brominated natural products, caelestines A−D (14), have been isolated from the Australian ascidian Aplidium caelestis. The structures of 14 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 14 were tested against three mammalian cell lines (MCF-7, NFF, and MM96L) and a panel of microbial strains and showed only minor cytotoxicity.