Cerebrosides from a Far-Eastern Glass Sponge Aulosaccus sp.

Nine new cerebrosides 1a-d, 2a, 2b, 3a-c were found in the extract of a Far-Eastern glass sponge Aulosaccus sp. (class Hexactinellida). These β-D-glucopyranosyl-(1 → 1)-ceramides contain sphingoid bases (2S,3S,4R,11Z)-2-aminoeicos-11-ene-1,3,4-triol (in 1a-d), (2S,3S,4R,13Z)-2-aminoeicos-13-ene-1,3,4-triol (in 2a, b) and (2S,3S,4R,13S*,14R*)-2-amino-13,14-methylene-eicosane-1,3,4-triol (in 3a-c), which are N-acylated by (2R,15Z)-2-hydroxydocos-15-enoic (in 1a, 2a, 3a), (2R,16Z)-2-hydroxytricos-16-enoic (in 1b, 2b, 3b), (2R,17Z)-2-hydroxytetracos-17-enoic (in 1d) and (2R)-2-hydroxydocosanoic (in 1c, 3c) acids. The monoenoic and cyclopropane-containing sphingoid bases of compounds 1a-d, 2a, 2b, 3a-c have not been found previously in any sphingolipids. The structures of the cerebrosides were elucidated on the basis of (1)H-, (13)C-NMR spectroscopy, mass spectrometry, optical rotation data and chemical transformations. A simplified method for the assignment of the absolute configuration of 2-hydroxy fatty acids by GC analysis of their (2R)- and (2S)-oct-2-yl esters was proposed.