Isolation and structure determination of Pachybasium cerebrosides which potentiate the antifungal activity of aculeacin

A set of four cerebrosides was isolated from a Pachybasium species and purified by preparative reversed-phase HPLC. All four products displayed activity in a natural product screen aimed at detecting novel cell wall-active antifungal agents based on synergy with the known glucan synthetase inhibitor, aculeacin. Based on degradation studies, fast atom bombardment mass spectrometry and 13C and high field 1H NMR techniques, the structure of the major cerebroside was determined to be (4E,8E)-N-D-2'-hydroxy-(E)-3'- hexadecenoyl-1-O-beta-D-glucopyranosyl-9-methyl-4,8-sphingadiene. The other components were found to be the corresponding 2'-hydroxypalmitic acid analog with one less double bond and an analogous pair containing 2'-hydroxystearic acid with and without the 3' double bond.