Two (Z)-Dehydrobutyrine-Containing Microcystins from a Hepatotoxic Bloom of Oscillatoria agardhii from Soulseat Loch, Scotland

Two (Z)-dehydrobutyrine(Dhb)-containing microcystins, [d-Asp3, (Z)-Dhb7]microcystin-HtyR (1) and [d-Asp3, (Z)-Dhb7]microcystin-LR (2), were isolated from a hepatotoxic bloom of the cyanobacterium Oscillatoria agardhii from a freshwater lake in Scotland. The geometrical structure of the Dhb units in the microcystins was determined as Z on the basis of NOE and ROESY experiments.