Enantiomerically pure chiral pyridino-crown ethers: synthesis and enantioselectivity toward the enantiomers of α-(1-naphthyl)ethylammonium perchlorate

Abstract

Seven new enantiomerically pure chiral pyridino-crown ethers ( S,S)- 4–( R,R)- 10 were prepared. Three of them [( S,S)- 4, ( S,S)- 7 and ( R,R)- 10] contain one, and two of them [( S,S)- 5 and ( S,S)- 8] contain two linker chains with a terminal double bond. These linker chains were connected to the carbon atom at position 9 (opposite the pyridine moiety) of the macrocycle. The terminal double bond of the linker makes it possible to attach these ligands to silica gel to obtain chiral stationary phases (CSPs). The enantioselectivity of the new ligands toward the enantiomers of α-(1-naphthyl)ethylammonium perchlorate (NEA) was also determined by a titration 1H NMR method.