Abstract
The acid-base and complexing properties of diastereoisomers of phosphonodipeptides containing glycyl, L-alanyl. L-leucyl and L-phenylalanyl and terminal 1-aminoethylphosphonic acid residues were studied pH-metrically at 25 degrees C and at an ionic strength of 0.1 mol dm(-3) (KNO3).
The protonation and complex-formation stability constants with Co2+, Ni2+, CU2+ and Zn2+ indicate the presence of the same types of complexes and the same tendencies as in the aminomethylphosphonic acid series. In contrast to the common dipeptides, the differences found for diastereoisomers are much higher, probably due to stronger interaction between the hydrophobic and hydrophilic parts of the molecule.
Crystal structure determinations confirmed the absolute configurations of S,S-PhCH(2)CH(NH2)CONHCH(Me)PO3H2 and S,R-PrCH2CH(NH2)CONHCH(Me)PO3H2. The distances and bond angles found show that the peptide bond is not influenced by the phosphonic group.