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.