More Clues To Biotoxin Assembly

A newly discovered natural product is providing additional hints about how algae construct deadly toxins (Org. Lett., DOI: 10.1021/ol801243n). Ladder polyethers, named for their runglike structures, are toxins found in ecologically devastating algal blooms called red tides. In 1985, Columbia University's Koji Nakanishi suggested that the polyethers could arise from a cascade of epoxide-opening reactions, but it's still not clear how the ladders' fused ether rings are assembled. Now, a team led by Jeffrey L. C. Wright of the Center for Marine Science at the University of North Carolina, Wilmington, has detected trace amounts of brevisamide, a compound featuring just a single ether ring, in algae extracts. Brevisamide's structure, Wright says, supports the notion that an epoxide-opening pathway generates the ether ring. The structure also indicates the direction in which biosynthetic proteins assemble the carbon skeleton. Compared with other types of natural products, researchers know little about how these toxins are made, so "each new clue strongly influences our evolving hypothesis," says Timothy F. Jamison of MIT, who also explores ladder polyether biosynthesis.