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.
On the stereochemical control of complexation in tetrahydropyranoid podand ionophores
作者:Shawn D. Erickson、W. Clark Still
DOI:10.1016/s0040-4039(00)97593-2
日期:——
To test a proposal that stereochemistry can be used rationally to control the binding properties of ionophores, a new podand (3) has been prepared and studied. Unlike the previously prepared stereoisomeric podand 2 which has substitution and stereochemistry which enforces a single tetradentate binding conformation, 3 has been designed to avoid conformations in which all four oxygens can simultaneously