thoxycarbonyl (Fmoc) amino-2-deoxy-a-d-glucuroniside was immobilized on Rink resin. After deprotection of the Fmoc group with piperidine, an Fmoc-protected amino glucuronic acid was added and amide formation was promoted by TATU [O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate]. Iteration of this procedure culminated in the construction of a tetramer. Some difficulties encountered in immobilizing the first sugar residue may have been due to steric congestion at the resin surface. Subsequent couplings readily occurred, suggesting that the first residue may have served to extend the reaction centers away from the polymer bead (Fig. 28).
The Ichikawa group also made amido-linked oligomers derived from amino C-glycoside carboxylic acids . A Boc-protected ^-sugar amino acid was conjugated to phenylalanine and subsequently deprotected to give the free amine, which was coupled to another Boc-protected monomer. Diethylphosphoryl cyanide and triethyl-amine were used to activate the acid for coupling in the solution phase. A tetramer was synthesized and subsequently sulfated to increase solubility and to introduce negative charge (Fig. 29).
This material was designed as a potential inhibitor of HIV replication, since it was known that sulfated polymeric carbohydrates inhibit HIV entry into T cells. Syncytium formation was completely blocked when CD4 cells were infected with
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