Costatone C-A New Halogenated Monoterpene from the New Zealand Red Alga .

Red algae of the genus have been a rich source of halogenated monoterpenes. Herein, a new cyclic monoterpene, costatone C (), was isolated from the extract of collected in New Zealand, along with the previously reported (1,5)-1,6-dichloro-2-methylhepta-1,5-dien-3-ol (). Elucidation of the planar structure of was achieved through conventional NMR and (-)-HR-APCI-MS techniques, and the absolute configuration by comparison of experimental and DFT-calculated ECD spectra. The absolute configuration of was determined using Mosher's method. Compound showed mild antibacterial activity against and . The state of taxonomy and its implications upon natural product distributions, especially across samples from specimens collected in different countries, is also discussed.