7-Epi-30-Methyloscillatoxin D From an Okinawan Cyanobacterium Okeania hirsuta

Some aplysiatoxin-related compounds have been isolated from an Okinawan cyanobacterium Okeania hirsuta. The structure of a natural product isolated as 30-methyloscillatoxin D (1a) from this cyanobacterium in our previous report was re-investigated and revised to be a 7-epimer of 30-methyloscillatoxin D (4a) using precise NMR analysis. The synthesis of O-Me-7-epi-30-methyloscillatoxin D (4b) led to confirmation of the stereochemistry of 4a. This is the first report of a 7-epi-type aplysiatoxin-related compound from a natural source.