Stereoselective Interaction of Amino-acids and Metal Complexes

Abstract

STEREOSELECTIVE effects frequently occur¹ in the formation and reactions of optically active co-ordination compounds. The formation of ions of the type [Co(L-dipeptide)₂]⁻ shows^2,3 very marked stereoselectivity which may be attributed to the three point attachment⁴ of the dipeptide acting as a terdentate ligand, giving a puckered chelate ring. Similarly, peptides of the type gly-Lα, α being an amino-acid, react⁵ with the ion D[Coen₂(H₂O) (OH)]²⁺ more rapidly than with its enantiomer, through three-point attachment. Related three-point attachment can also occur with amino-acids containing a polar side chain. For example, we recently demonstrated⁶ that L-glutamate ion reacts specifically with DL[Coen₂(H₂O)₂]³⁺ giving D( + )[Coen₂(Lglu)]⁺.