Metallkomplexe mit biologisch wichtigen Liganden, LXVII [1] . Synthese von α‐Aminosäuren aus Palladium(II)‐ und Rhodium(III)‐koordinierten Iminen und Oximen von α‐Oxocarboxylaten

Metal Complexes of Biologically Important Ligands, LXVII [1] . – Synthesis of α‐Amino Acids from Palladium(II)‐ and Rhodium(III)‐Coordinated Imines and Oximes of α‐Oxocarboxylates The bis‐chelate complexes Pd[O 2 CC(R 1 )=NOR 2 ] 2 ( 1 ) and Pd[O 2 CC(R 1 )=NR 2 ] 2 ( 2 , R 2 optically active substituent) are synthesized by template condensation of an α‐oxocarboxylic acid with a hydroxylamine or amine component, respectively. Similarly, the Rh(III) complexes Cp * Rh(Cl)[O 2 CC(R)=N(CHMePh)] ( 3a : R = H, 3b : R = Me) were obtained from α‐oxocarboxylic acids and optically active 1‐phenylethylamine. Catalytic hydrogenation of 1 and 2 gives directly the free α‐amino acids with, in case of 2 , ee's between 0 and 36%. Nucleophilic attack by the carbanions of RC(O)CH 2 CO 2 Et and H 2 NCH(CO 2 Et) 2 at the imino carbon atom of 3a leads to the α‐amino carboxylato complexes 4 and 5 . – Compounds 4a and 5 have been characterized by X‐ray diffraction. Reaction of 3a with NaBH 4 or NaBD 4 followed by decomposition of the complex with HCl yields N ‐substituted glycine and N ‐substituted α‐deuterio‐glycine, respectively. The diastereoselectivity (70:30) of the α‐deuteration could be determined by NMR spectroscopy.