American Chemical Society
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Spirocyclic Zwitterionic λ5Si-Silicates with Two Bidentate Ligands Derived from α-Amino Acids or α-Hydroxycarboxylic Acids:  Synthesis, Structure, and Stereodynamics

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journal contribution
posted on 2004-11-10, 00:00 authored by Reinhold Tacke, Rüdiger Bertermann, Christian Burschka, Simona Dragota, Martin Penka, Ingo Richter
A series of zwitterionic λ5Si-silicates with a (2,2,6,6-tetramethylpiperidinio)methyl group and two identical bidentate ligands derived from glycine, (S)-alanine, (S)-phenylalanine, glycolic acid, (S)-lactic acid, (S)-3-phenyllactic acid, or (S)-mandelic acid were synthesized and structurally characterized (solution and solid-state NMR spectroscopy; single-crystal X-ray diffraction). The chiral λ5Si-silicates with ligands derived from optically active α-amino acids or α-hydroxycarboxylic acids were isolated as enantiomerically and diastereomerically pure compounds that undergo a (Λ)/(Δ)-epimerization in solution.