Synthesis of the Core Tetrasaccharide of Trypanosoma cruzi Glycoinositolphospholipids: Manp(α1→6)-Manp(α1→4)-6-(2-aminoethylphosphonic acid)-GlcNp(α1→6)-myo-Ins-1-PO4

[structure: see text] Synthesis of the core tetrasaccharide Manp(alpha1-->6)-Manp(alpha1-->4)-6-(2-aminoethylphosphonic acid)-GlcNp(alpha1-->6)-myo-Ins-1-PO4, found in glycoinositolphospholipids of Trypanosoma cruzi parasites, is described. The key building block, 6-O-(2-azido-3-O-benzyl-6-O-((2-benzyloxycarbonylaminoethyl)phosphonic acid benzyl ester)-2-deoxy-alpha-D-glucopyranosyl)-1-di-O-benzylphosphoryl-4,5-O-isopropylidene-2,3-O-(D-1,7,7-trimethyl[2,2,1]bicyclohept-6-ylidene)-D-myo-inositol, was synthesized using a partially protected glucosyl D-camphorinositolphosphate and a (2-benzyloxycarbonylaminoethyl)phosphonic acid derivative in a regioselective phosphonate esterfication. Elongation with ethyl 2-O-benzoyl-3,4,6-tri-O-benzyl-alpha-D-mannopyranosyl-(1-->6)-2,3,4-tri-O-benzyl-1-alpha-D-thiomannopyranoside using dimethyl(methylthio)sulfonium trifluoromethanesulfonate gave a fully protected tetrasaccharide which was successfully deprotected subsequently with sodium methoxide, sodium in liquid ammonia, and aq hydrochloric acid to give title compound.