DIFFERENTIAL REACTIVITY PATTERN FOR THE CONDENSATION-REACTIONS OF COPPER(II) COMPLEXES OF DL-AMINO AND L-AMINO-ACIDS

The condensation reactions of copper(II) complexes of DL and L forms o f alanine, serine and threonine with aliphatic aldehydes reveal differ ential reactivity for the bis(amino acidato)copper(II) complexes. The reaction of [CU(DL-ala)2] (where ala = alaninato anion) with formaldeh yde and ammonia, at an acidic pH of 5, yields a pentamethylenediaza gr oup containing product, -cyclo[3.3.1]nonane)di(2-methylacetato)]copper (II) 1, but at higher pH conditions (pH > 8.0), yields the known oxazo lidine group containing product, abis(4-methyloxazolidine-4-carboxylat o)-copper(II) 2. However, the reaction of [CU(L-ala)2] with formaldehy de and ammonia at pH 8.5 is known to yield an optically active isomer of 1, viz. cyclo-[3.3.1]nonane)di(2-methylacetato)]copper(II) la. Thou gh the latter reaction also yields the oxazolidine group containing pr oduct 2 at very basic pH (>10), the formation of 2 reveals racemizatio n during the reaction process. Similarly, whereas the copper(II) compl exes of DL-serine and DL-threonine readily undergo condensation reacti ons with aldehydes such as formaldehyde, propionaldehyde, butyraldehyd e and valeraldehyde, yielding oxazolidine group containing products, t he corresponding L-amino acidatocopper(II) complexes do not undergo co ndensation under the same experimental conditions except in the case o f formaldehyde, demonstrating differential reactivity Of DL- and L-ami no acidatocopper(II) complexes. The crystal structures of the products obtained from the reactions of [CU(DL-ser)2] (ser = serinato anion) a nd [CU(DL-thr)2] (thr = threoninato anion) with formaldehyde, panediyl )bis(oxazolidine-4-carboxylato)]copper(II) sesquihydrate 3 and )bis(5- methyloxazolidine-4-carboxylato)]copper(II) monohydrate 4, respectivel y, have been determined. Complex 3 crystallizes in the triclinic space group P1BAR, a = 10.802(2), b = 11.039(2), c = 13.460(3) angstrom, al pha = 75.14(3), beta = 69.57(3), gamma = 87.53(3)-degrees and Z = 4. C omplex 4 also crystallizes in the triclinic space group P1BAR, a = 7.3 88(2), b = 1 0.01 7(2), c 11.485(2) angstrom, alpha = 11 5.27(3), beta = 101.89(3), gamma = 91.79(3)-degrees and Z = 2.