Synthesis and biological activities of glycosphingolipid analogues from marine sponge Aplysinella rhax

A novel glycosphingolipid, β-d-GalNAcp(1 → 4)[α-d- Fucp(1 → 3)]-β-d-GlcNAcp(1→)Cer (1), isolated from the marine sponge Aplysinella rhax, has a unique structure, with d-fucose and N-acetyl-d-galactosamine attached to a reducing-end N-acetyl-d-glucosamine through an α1 → 3 and β1 → 4 linkage, respectively. We synthesized glycolipid analogues carrying a 2-branched fatty alkyl residue or a 2-trimethylsilyl ethyl residue in place of ceramide (2 and 3), non-natural type trisaccharide analogue containing an l-fucose residue (4), and other analogues (5 and 6). Among these prepared compounds, 2 showed the most potent nitric oxide (NO) production inhibitory activity against LPS-activated J774.1 cells. In addition, their structure–activity relationships were established.