(1'Z,4'Z,7'Z,10'Z)-(1S,2S,4R,5S,6R)-2-methoxy-6-(methoxymethyl)oxy-4-trideca-1',4',7',`0'-tetraenyl-3-oxabicyclo[3.3.0]octane

5-O-methoxymethoxybacillariolide I