1(3),2-Diacylglyceryl-3(1)- O-2′-(hydroxymethyl)( N, N, N,-trimethyl)-β-alanine (DGTA): A novel betaine lipid from Ochoromonas danica (Chrysophyceae)

Abstract

The structure of lipid B, another betaine lipid from Ochromonas danica (Crysophyceae) has been elucidated by NMR, MS and IR data from the intact lipid and from derivatives obtained by chemical degradation. The structure of 1(3),2-diacylglyceryl-3(1)- O-2′- (hydroxymethyl)( N, N, N-trimethyl)-β-alanine (DGTA) has been assigned to the intact lipid which is a structural isomer of the already known homoserine lipid or 1(3),2-diacylglyceryl-3(1)- O-4′-( N, N, N-trimethyl)-homoserine (DGTS). 1(3),2- Diacylglyceryl-3(1)- O-2′-(hydroxymethyl)-propenoic acid was obtained from DGTA by deamination in chloroform with traces of formic acid. 1(3),2-diacylglycerol-3(1)- O-2′-(hydroxymethyl)-propanoic acid methyl ester was formed by treatment of DGTA with diazomethane in the presence of formic acid and by subsequent hydrogenation. From this compound, the corresponding diacetyl derivative was obtained by trans-esterification and acetylation. The diacetate was identical with synthetic 1(3),2-diacetylglyceryl-3(1)- O- 2′-(hydroxymethyl)-propanoic acid methyl ester, the preparation of which, starting from isopropylideneglycerol and 2-(bromomethyl)-acrylic acid methyl ester, is described. DGTA accounts for approximately 5% of the total lipids of O. danica. The major fatty acids of DGTA are 22:5 (42%), 18:0 (15%), 20:4 (13%); 20:2 (6%), 18:1 (5%), 20:3 (4%) 18:2 (4%), 22:4 (3%) and 16:0 (2%). From DGTA, trimethylamine is produced by a spontaneous deamination.