Blockwise synthesis of a pentasaccharide structurally related to the mannan fragment from the Candida albicans cell wall corresponding to the antigenic factor 6

A spacer-armed pentasaccharide structurally related to a fragment of the mannan from the cell wall of the fungus Candida albicans and corresponding to the antigenic factor 6 has been synthesized. This compound, comprising two α-(1→2)- and three β-(1→2)-linked mannose residues, was prepared by glycosylation of a selectively protected α-(1→2)-dimannoside bearing an aglycone spacer and a free OH group at atom C(2´) with a β-(1→2)-trimannoside glycosyl donor. The successful synthesis evidences that large β-(1→2)-oligomannoside donor blocks can be used for the preparation of oligosaccharides including extended sequences of repeating β-(1→2)-linked mannose residues.