ZINC(II) COMPLEXES OF PHOSPHONIC ACID ANALOGS OF GLUTAMIC-ACID

The stoichiometries and stability constants of proton and zinc(II) com plexes of two phosphonic acid analogues Of glutamic acid and three ana logues of pyroglutamic acid (5-oxopyrrolidine-2-carboxylic acid) have been determined potentiometrically at 25 degrees C and at ionic streng th 0.2 mol dm(-3) (KCl). Complementary studies by means of P-31 and C- 13 NMR spectroscopy were also undertaken and indicated that the analog ue obtained by the replacement of the gamma-carboxylic group of glutam ic acid,by a phosphonic acid moiety and the phosphonic acid analogue o f pyroglutamic acid exhibit predictable properties when complexing zin c(II) ions. The analogue obtained by the replacement of the alpha-carb oxylic group by a phosphonic acid group underwent chemical transformat ion upon reaction with zinc(II) ions under-neutral and alkaline condit ions yielding most probably a cyclic phosphonamidate composed of two l igand molecules. The crystal structures of some analogues of pyrogluta mic acid were also determined.