The first naturally occurring α‐methoxylated branched‐chain fatty acids from the phospholipids of Amphimedon complanata

The phospholipid fatty acid composition of the sponge Amphimedon complanata was reinvestigated, and the 2‐methoxy‐13‐methyltetradecanoic acid, 2‐methoxy‐14‐methylpentadecanoic acid, and 2‐methoxy‐13‐methylpentadecanoic acid were identified for the first time in nature. Structure characterization was accomplished by means of gas chromatographic retention times and gas chromatography‐mass spectrometry. These acids could have originated from bacteria in symbiosis with the sponge.