Synthesis of polysaccharide derivatives bearing pyridine N-oxide groups and their use as asymmetric organocatalysts

Novel amylose and cellulose derivatives bearing pyridine N-oxide groups were synthesized, and their performance as asymmetric organocatalysts was investigated. The amylose derivatives bearing 3-pyridyl N-oxide groups enantioselectively catalyzed the allylation of benzaldehyde by allyltrichlorosilane with different enantiomeric excesses (ee; 13-32% ee), depending on the degree of substitution of the pyridine N-oxide. In contrast, the corresponding cellulose derivatives showed the opposite enantioselectivity with much lower ee (2-11% ee). These results suggest that the higher-order structures of polysaccharides play an important role in the enantioselective allylation of benzaldehyde.