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 (2 S ,3 S ,4 R ,11 Z )-2-aminoeicos-11-ene-1,3,4-triol (in 1a – d ), (2 S ,3 S ,4 R ,13 Z )-2-aminoeicos-13-ene-1,3,4-triol (in 2a , b ) and (2 S ,3 S ,4 R ,13 S *,14 R *)-2-amino-13,14-methylene-eicosane-1,3,4-triol (in 3a – c ), which are N -acylated by (2 R ,15 Z )-2-hydroxydocos-15-enoic (in 1a , 2a , 3a ), (2 R ,16 Z )-2-hydroxytricos-16-enoic (in 1b , 2b , 3b ), (2 R ,17 Z )-2-hydroxytetracos-17-enoic (in 1d ) and (2 R )-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 (2 R )- and (2 S )-oct-2-yl esters was proposed.