Nickel complexes amino acid esters

It has been known for many years that the rate of hydrolysis of a-amino acid esters is enhanced by a variety of metal ions such as copper(II), nickel(II), magnesium(H), manganese(II), cobalt(II) and zinc(II).338 Early studies showed that glycine ester hydrolysis can be promoted by a tridentate copper(II) complex coupled by coordination of the amino group and hydrolysis by external hydroxide ion (Scheme 88).339 Also, bis(salicylaldehyde)copper(II) promotes terminal hydrolysis of the tripeptide glycylglycylglycine (equation 73).340 In this case the iV-terminal dipeptide fragment... 

Originally devised as a method for the conversion of amino acids or amino acid esters to aldehydes. The Akabori reaction has been modihed for use in the determination of C-terminal amino acids by performing the reaction in the presence of hydrazine and for the production of derivatives useful for mass spectrometric identihcation. See Ambach, E. and Beck, W., Metal-complexes with biologically important ligands. 35. Nickel, cobalt, palladium, and platinum complexes with Schiff-bases of... 

The coordination of optically active amino acids and their methyl esters to nickel(II) complexes of l,2-bis(2-(5)-aminomethyl-l-pyrrolidinyl)ethane (24 R = H) and l,2-bis(2-(S)-N-methyl-aminomethyl-l-pyrrolidinyl)ethane (24 R=Me) has been studied.98 Some amino acidate ions coordinate stereoselectivity, as do their methyl esters, so that base hydrolysis of the esters proceeds stereoselectively. 

Another very important class of chiral partitioning systems involves coordination of the selector and selectand to a metal. Notable examples are the Cu(II) complexes of a-amino acids, such as L-proline [2, 19] and N,N-di-n-propyl-L-alanine [20] and of similar zinc and nickel derivatives, e.g. Ni(L-proline n-octylamide)2 [21]. With N,N-di-n-propyl-L-alanine, used as additive to the mobile phase in HPLC, a particularly wide range of compounds could be resolved, including free a-amino acids, their dansyl and ester derivatives, dipeptides, a-amino caprolactame, as well as a-hy-droxy acids [22]. 

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