Synthesis of octyl O- and S-glycosides related to the GPI anchor of Trypanosoma brucei and their in vitro galactosylation by trypanosomal alpha-galactosyltransferases.

Octyl O- and S-glycosides of mono- to tri-saccharides related to the core structure alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->6)-alpha-D-Manp of the GPI anchor of Trypanosoma brucei have been prepared via regioselective protodesilylation and glycodesilylation of octyl O- and S-glycosides of 2-O-benzoyl-4,6-O-(1,1,3,3-tetraisopropyl-1,3-disiloxane-1, 3-diyl)-alpha-D-mannopyranoside. The synthetic saccharides have been used as substrates for enzymatic alpha-galactosylation with membrane fractions of bloodstream forms of T. brucei strain 427 variants MITat 1.4, MITat 1.2, and MITat 1.5, respectively.