Zooxanthellatoxin-A, a potent vasoconstrictive 62-membered lactone from a symbiotic dinoflagellate

Spectroscopic studies and chemical degradation experiments of zooxanthellatoxin-A, (ZT-A), a member of macrolide group of compounds, indicate its structure to contain a 62-membered lactone ring, as confirmed by the formation of the corresponding seco acid. One methylene group contains a heteroatom, which is revealed by the HMQC spectrum of ZT-A in CD30D. Two sets of high-field proton resonances and C-H coupling data suggest a spiroacetal structure of ZT-A.