natural products chemistry of Bonnemaisonia nootkana, B. asparagoides, B. hamifera and Trailliella intricata are described. In contrast to the chemistry of the closely relatedalga Asparagopsis, Bonnemaisonia spp. do not produce halomethanes, but instead an array of C7-C9 halogen-containing ketones, alcohols and carboxylic acids. Biomimetic syntheses of these compounds suggest they are precursors and