Structure and stereochemistry of a novel bioactive sphingolipid from a Calyx sp.

Bioassay-directed fractionation of a sponge of the genus Calyx using a yeast bioassay for DNA-damaging agents yielded the novel sphingolipid calyxoside (1) as the major bioactive constituent. The structure of 1 was assigned as 1,3,26-trihydroxy-2,27-diaminooctacosan-18-one-1-β-d-glucoside by 1H- and 13C NMR, DEPT, DQCOSY, HMQC, and HMBC spectra. The carbonyl group was located at C-18 by analysis of the EI-MS fragmentation of the amino derivative of its aglycone pentaacetate. Its absolute configuration was determined as 2S,3R,26S,27S by analysis of the 1H NMR and CD spectra of its aglycone pentabenzoate.