CHIRAL LIPOPHILIC LIGANDS .2. CU(II)-MEDIATED TRANSPORT OF ALPHA-AMINO-ACIDS ACROSS A BULK CHLOROFORM MEMBRANE

A number of achiral (1 - 4) and chiral (5 - 10) 1,2-diamino ethane der ivatives bearing on one or both nitrogen atoms long paraphrenic chains have been synthesized and successfully tested as carriers for the tra nsport of Cu(II) and a-amino acids across a bulk chloroform membrane f rom a buffered (pH=5.5) source phase to a receiving solution of EDTA, This, being a highly hydrophilic ligand with an affinity for Cu(II) se veral order of magnitude larger than that of the carrier, allows an ef fective ''uphill'' co-transport of ions and amino acids. The results i ndicate that the transport occurs via the formation of a ternary compl ex comprising Cu(II), the lipophilic diamine, and the amino acid. The lipophilicity of the amino acid is the main factor affecting the ram o f transport using the same carrier on me other hand for the same amino acid the best carrier is that having affinity constant for Cu(II) clo se to that of the amino acid transported, The rate of transport is app arently governed by the ram of release of the metal ion and the amino acid from the source phase to the organic phase. The enantioselectivit ies observed in the co-transport of natural amino acids employing chir al ligands are generally modest; in the best cases, the enantioselecti vity ratios (the initial rates of transport of the faster enantiomer r elative to the slower) are slightly higher than 2. The enantioselectiv ity appears to depend more on thermodynamic rather than kinetic factor s.