Cyclic polylactones and their cyclic polyorthoester valence tautomers: Potential ionophores

The geometries and energies of the cyclic hexamer (9) of glycolic acid, and its polycyclic orthoester valence tautomer (10) have been studied by ab in itio molecular orbital calculations at the HF/6-31G* and MP2//F/6-31G* leve ls of theory. Both molecules are preorganised to bind metal ions in both en dohedral and exohedral modes. The binding of 9 and 10 with Li+, Na+, K+, Be 2+, Mg2+, B3+ and Al3+ have been examined, and the energies and geometries of the resulting complexes are discussed. (C) 2000 Elsevier Science Ltd. Al l rights reserved.