Does local chain conformation affect the chiral recognition ability of an amylose derivative? Comparison between linear and cyclic amylose tris(3,5-dimethylphenylcarbamate).

Coated-type chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were prepared from three cyclic amylose tris(3,5-dimethylphenylcarbamate) (cADMPC) samples, of which weight-average molar mass (M) ranges from 19 to 91 kg mol, and from three linear ADMPC samples ranging in M from 25 to 90 kg mol. CSPs made of cADMPC showed appreciably different chiral separation ability comparing with those for ADMPC with a mixed eluent of n-hexane and 2-propanol. Local conformation plays an important role for the chiral separation taking into account that the local helical structure of cADMPC in dilute solution is extended comparing with ADMPC. Immobilized-type CSPs were also prepared from enzymatically synthesized linear and cyclic amylose samples with 3-(triethoxysilyl)propylcarbamate linkers (ADMPCi and cADMPCi) of which M's are in the range from 18 to 130 kg mol. When we choose quite high linker contents, CSPs of cADMPCi were fairly close to those of ADMPCi. This suggests that local conformations of ADMPCi and cADMPCi are similar in the stationary phase since they are crosslinked to the other polymer chains with multiple points on the polymer chain.