Enantioselective complexation of organic ammonium ions by simple tetracyclic podand ionophores
摘要:
A series of enantiomerically pure, C2-symmetric tetracyclic podands are synthesized and studied. These host molecules have methyl substitution, which allows only a few low-energy conformations, and they form well-defined complexes with chiral ammonium salts. With derivatives of alpha-phenethylammonium hexafluorophosphate as guests, binding enantioselectivity ranges from approximately 0 to 60% ee. X-ray structures of several podand/chiral ammonium perchlorate complexes are described along with a conformational analysis of the podands and their complexes.