Abstract
A novel galactosylalkylglycerol modified with a long-chain cyclic acetal at the sugar moiety, 3-O-(4′6′-plasmalogalactosyl) 1-O-alkylglycerol, was isolated from equine brain. The presence of cyclic acetal linkage, its linked position, and the length of the acetal chain of the natural plasmalo lipid were determined by proton NMR spectroscopy and fast-atom bombardment–mass spectrometry, as well as gas chromatography–mass spectrometry and gas–liquid chromatography. To identify the isomeric stereostructure of the natural product, the plasmalo derivative was chemically synthesized from 3-O-galactosyl 2-O-acyl 1-O-alkyl glyceride through acetalization after deacylation. As a result, the direction and position of the acetal chain of the natural plasmalo lipid were characterized as an “endo”-type 4′,6′-O-acetal derivative linked to galactoside by comparison with the NMR data of the synthesized product. The chain lengths of alkyl and acetal groups were C14 for the former and C16 and C18 for the latter, and those for the latter group were mostly similar to those of plasmalogalactosyl ceramide, which was previously isolated from equine brain.—Yachida, Y., M. Kashiwagi, T. Mikami, K. Tsuchihashi, T. Daino, T. Akino, and S. Gasa. Novel plasmalogalactosylalkylglycerol from equine brain.
Highlights
A novel galactosylalkylglycerol modified with a long-chain cyclic acetal at the sugar moiety, 3-O-(46-plasmalogalactosyl) 1-O-alkylglycerol, was isolated from equine brain
Their chemical structures, including the presence and chain length of the fatty aldehyde, were characterized mainly with mass spectra using fast-atom bombardment–mass spectrometry (FAB–MS), and by methylation analysis followed by analysis by gas chromatography–mass spectrometry (GC–MS)
We describe for the first time isolation from equine brain, synthesis and identification of the stereochemical structure of a plasmalo derivative having a galactosyl glycerol skeleton
Summary
A novel galactosylalkylglycerol modified with a long-chain cyclic acetal at the sugar moiety, 3-O-(46-plasmalogalactosyl) 1-O-alkylglycerol, was isolated from equine brain. Conjugated lipids with long-chain fatty aldehyde of glycosphingolipid, termed plasmalolipids, were isolated for the first time from normal human brain as novel modified glycolipids [9, 10], in which the modification was reported to occur at 3,4-O- and 4,6-O- on Gal of GalCer [9] and Gal sphingosine (psychosine) [10] to form cyclic acetal linkage Their chemical structures, including the presence and chain length of the fatty aldehyde, were characterized mainly with mass spectra using fast-atom bombardment–mass spectrometry (FAB–MS), and by methylation analysis followed by analysis by gas chromatography–mass spectrometry (GC–MS). The isomeric stereostructure of natural plasmaloGalCer from equine brain, which can have two isomers with different directions of the fatty acetal chain, endo- and exotypes, was characterized as the former type by proton nuclear magnetic resonance spectroscopy (NMR) by us, after chemical synthesis of the plasmalolipid [12] These plasmalo derivatives are modified glycosphingolipids, not glycoglycerolipids. We describe for the first time isolation from equine brain, synthesis and identification of the stereochemical structure of a plasmalo derivative having a galactosyl glycerol skeleton
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