A first total synthesis of ganglioside HLG-2

Article abstract of DOI:10.1002/chem.200802706

A first synthesis of the neuri-tegenic ganglioside HLG-2, which was identified in extracts of the sea cucumber Holothuria leucospilota, is described. The characteristic sequence of the trisaccharide part, α-N-glycolylsial-yl-(2,4)-& α-N-acetylsialyl-(2,6)-glucoside, was efficiently assembled by coupling of a highly active N-2,2,2-trichloro- ethoxycarbonyl (Troc)-protected sialyl donor and a 1,5-lactamized sialyl ac- ceptor with high stereoselectivity. The corresponding trisaccharyl imidate donor was directly glycosidated with the primary hydroxyl group of the ceramide part, producing protected HLG-2 in relatively high yield, global deprotection of which furnished ganglioside HLG-2 in highly pure form.