Coordination of biologically important [alpha]-amino acids to calcium(II) at high pH: Insights from crystal structures of calcium [alpha]-aminocarboxylates

A series of calcium [alpha]-aminocarboxylates are prepared by refluxing aqueous solutions/suspensions of calcium hydroxide and the respective [alpha]-amino acid and their crystal structures and spectroscopic properties are investigated. The structural diversity is observed with the binding modes of the aminocarboxylate ligands and the calcium environment, and besides terminal aminocarboxylate coordination, there are three diferent types of aminocarboxylate bridges.