Marine Natural Products. XXIX. Heterosigma-glycolipids I, II, III, and IV, Four Diacylglyceroglycolipids Possessing .OMEGA.3-Polyunsaturated Fatty Acid Residues, from the Raphidophycean Dinoflagellate Heterosigma akashiwo.

Heterosigma-glycolipids I (1), II (2), III (3), and IV (4), four new Diacylglyceroglycolipids possessing ω3-polyunsaturated fatty acid residues, were isolated from the cultured raphidophycean dinoflagellate Heterosigma akashiwo.Based on enzymatic partial hydrolysis using lipase and physicochemical evidence. the structures of heterosigma-glycolipids I (1), II (2), III (3), and IV (4) have been determined as (2'S)-2', 3'-di-O-(6, 9, 12, 15-octa-decatetraenoyl)glyceryl β-D-galactopyranoside, (2'S)-2'-O-(6, 9, 12, 15-octadecatetraenoyl)-3'-O-(5, 8, 11, 14, 17-eicosapentaenoyl)glyceryl β-D-galactopyranoside, (2'S)-2'-O-(6, 9, 12, 15-octadecatetraenoyl)-3'-O-(3, 6, 9, 12, 15-octadecapentaenoyl)glyceryl β-D-galactopyranoside, and (2'S)-2'-O-(5, 8, 11, 14, 17-eicosapentaenoyl)-3'-O-(6, 9, 12, 15-octadecatetraenoyl) glyceryl 6-O-(α-D-galactopyranosyl)-β-D-galactopyranoside, respectively.