Mantyl tagged oligo α (1 → 2) mannosides as Candida albicans β-mannosyl transferases substrates: a comparison between synthetic strategies

Fluorescent oligomannosides are important tools for the evaluation of mannosyl transferase activities and selectivities. In a project dealing with Candida albicans beta-mannosyl transferases, three mantyl tagged alpha (1 -> 2) oligomannosides were prepared by different ways: using all ester strategy compatible with the presence of an azido group suitable for direct click chemistry; and alternatively using the more classic benzyl protecting groups. Although more elegant, the all ester strategy has shown important limitations: reduced reactivity of mannosyl donors, and 3 -> 2 ester migration. Preliminary enzymatic studies have shown that the synthetic oligomannosides are efficient substrate of b-mannosyl transferases.