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.
Highly isotactic optically active methacrylate polymers by free radical cyclopolymerization
作者:Shiying Zheng、Dotsevi Y. Sogah
DOI:10.1016/s0040-4020(97)00974-5
日期:1997.11
Isospecificfreeradical cyclopolymerization of tartrate-based monomers gives polymers with very high optical rotations. Circular dichroism and polarimetric measurements suggest the polymers are rigid and ordered. Their high resistance to solvolysis suggests potential applications in chiral chromatography.