Crown Ethers in Enantioselective Synthesis

A research group at the Technical University, Budapest, has long been dealing with the synthesis and utilization of crown ethers and related molecules. A number of the sugar-based chiral crown ethers, as well as lariat ethers incorporating glucose, galactose, mannose and mannitol units in the hetero ring have been synthesized. The association constants of these compounds with Li + ,N a + ,K + and NH 4 + cations were measured, but the main point was to explore the possibilities offered by the chirality of the macrocycles. We wished to examine if the sugar-based crown ethers are capable for the discrimination of enantiomers and if they can bring about asymmetric induction as catalysts.