"Click chemistry" on polysaccharides: A convenient, general, and monitorable approach to develop β-1,3-glucans with various functional appendages

β-1,3-glucans having various functional appendages (β-lactoside, ferrocene, pyrene, and porphyrin) can be prepared in a convenient, quantitative, and regioselective manner through regioselective bromination/azidation on curdlan to afford 6-azido-6-deoxy-curdlan followed by chemo-selective [3+2]cycloadditions with various functional modules with a terminal alkyn. In addition to the aforementioned advantages, monitorablity is an additional advantage of this synthetic approach over the conventional direct modifications on polysaccharides, that is, the reaction can be easily monitored based on intensity of azido-peaks in in situ attenuated total reflection-infrared spectra. The resultant curdlan derivatives, especially that having lactoside-appendages, can interact with certain polynucleotides to form stable macromolecular complex that can bind to RCA₁₂₀ (β-lactoside recognition lectin).