Structure revision and absolute configuration of malhamensilipin A from the freshwater chrysophyte Poterioochromonas malhamensis.

Malhamensilipin A (2), a bioactive chlorosulfolipid initially reported in 1994 from the freshwater alga Poterioochromonas malhamensis, was reinvestigated for its structural and stereochemical features. HRESIMS data revealed that 2 possesses two sulfate groups rather than the one originally reported. A combination of J-based configurational and Mosher's analyses led us to assign its absolute configuration as 11R, 12S, 13S, 14R, 15S, and 16S. Finally, comparison of (1)H and (13)C NMR chemical shifts with synthetic standards confirmed that malhamensilipin A (2) possesses a terminal double bond of E configuration.