Kalkipyrone, a Toxic γ-Pyrone from an Assemblage of the Marine Cyanobacteria Lyngbya majuscula and Tolypothrix sp.

Kalkipyrone, a novel alpha-methoxy-beta,beta'-dimethyl-gamma-pyrone possessing an alkyl side chain, was isolated from an assemblage of the marine cyanobacteria Lyngbyamajuscula and Tolypothrix sp. Its structure, including stereochemistry, was determined by NMR, UV, and IR analysis and by GC-MS of the natural product and key derivatives. Kalkipyrone is toxic to brine shrimp (LD50 1 microg/mL) and gold fish (LD50 2 microg/mL) and is structurally related to the actinopyrones that were previously isolated from Streptomyces spp.