Chromatographic Resolution of α‐Amino Acids by (R)‐(3,3'‐Halogen Substituted‐1,1'‐binaphthyl)‐20‐crown‐6 Stationary Phase in HPLC

Three new chiral stationary phases (CSPs) for high‐performance liquid chromatography were prepared from R‐(3,3'‐halogen substituted‐1,1'‐binaphthyl)‐20‐crown‐6 (halogen = Cl, Br and I). The experimental results showed that R‐(3,3'‐dibromo‐1,1'‐binaphthyl)‐20‐crown‐6 (CSP‐1) possesses more prominent enantioselectivity than the two other halogen‐substituted crown ether derivatives. All twenty‐one α‐amino acids have different degrees of separation on R‐(3,3'‐dibromo‐1,1'‐binaphthyl)‐20‐crown‐6‐based CSP‐1 at room temperature. The enantioselectivity of CSP‐1 is also better than those of some commercial R‐(1,1'‐binaphthyl)‐20‐crown‐6 derivatives. Both the separation factors (α) and the resolution (Rs) are better than those of commercial crown ether‐based CSPs [CROWNPAK CR(+) from Daicel] under the same conditions for asparagine, threonine, proline, arginine, serine, histidine and valine, which cannot be separated by commercial CR(+). This study proves the commercial usefulness of the R‐(3,3'‐dibromo‐1,1'‐binaphthyl)‐20‐crown‐6 chiral stationary phase.