Synthesis and characterization of regioselectively substituted curdlan hetero esters with different ester groups on primary and secondary hydroxyl groups

Two kinds of regioselectively substituted curdlan hetero ester, 2,4-di-O-acetyl-6-O-propionyl-curdlan (CD24Ac6Pr) and 2,4-di-O-propionyl-6-O-acetyl-curdlan (CD24Pr6Ac), were synthesized. By repeating detritylation and esterification, a new method to remove trityl group from 6-O-trityl-curdlan without acyl migration was developed. Their molecular structures, thermal and mechanical properties and crystal structures were analyzed by NMR, TGA, DSC, tensile test and WAXD. It was concluded that the ester groups substituted on secondary hydroxyl groups at C2 and C4 positions play the decisive role in the melting behavior and crystalline formation of curdlan esters. Also, the mechanical properties of curdlan esters are controllable by the adjustment on its molecular structures.