Stereoselective interaction of a tridentate Schiff base complex of nickel(II) and amino acids
It has been observed that a tridentate Schiff base complex of nickel(II), triaquotribenzo-[b,f,j][1.5.9]-triazacyclodecinenickel(II), commonly called (TRI)Ni(OH2)32+, shows substantial stereoselectivity on complexing with several amino acids. This provides a convenient way to resolve (TRI)Ni(OH2)32+ using histidine as a resolving agent, and either ion exchange or perchlorate salt crystallization techniques.The resolved (TRI)Ni(OH2)32+ may then be used to resolve other amino acids or as a sensitive test of the stereochemistry of an amino acid. The test can be done on milligram quantities because of the insolubility of the complex perchlorate salt and because of the relatively large molecular rotation (2 × 105 deg at 283 nm) of (TRI)Ni(OH2)32+. The amino acid is easily released by treatment of the complex with dilute acid (Ph ≈ 2). The procedure has been tested with histidine, tyrosine, methionine, and phenylglycine.
A new synthesis of enantiomerically pure syn-(S)-β-hydroxy-α-amino acids via asymmetric aldol reactions of aldehydes with a homochiral Ni(II)-glycine/(S)-BPB Schiff base complex
