Synthesis of new enantiopure dimethyl- and diisobutyl -substituted pyridino-18-crown-6 ethers containing a halogen atom or a methoxy group at position 4 of the pyridine ring for enantiomeric recognition studies

New enantiomerically pure dimethyl-and diisobutyl-substituted pyridino-18-crown-6 ethers containing a halogen atom or a methoxy group at position 4 of the pyridine ring [(S,S)-1, (S,S)-2, (S,S)-3, (S,S)-4] have been synthesized.A new synthetic route and the solid state structure of the reported enantiopure dimethyl-substituted pyridino-18-crown-6 ether [(S,S)-5] containing a chlorine atom at position 4 of the pyridine ring are also described.These ligands are good candidates for enantiomeric recognition studies of protonated primary amines, amino acids and their derivatives.