463328-35-0Relevant academic research and scientific papers
Chiral quadridentate ligands derived from amino acids and some zinc complexes thereof
Niklas, Nicole,Walter, Olaf,Alsfasser, Ralf
, p. 1723 - 1731 (2000)
A series of three new quadridentate ligands was synthesized by reaction of the haloacetylated amino acid esters L-BrAc-Phe-OMe (4a), L-BrAc-Lys(Z)- OMe (4b), and ClAc-Gly-OEt (4c), respectively, with bis(picolyl)amine (bpa, 5). The obtained products L-bpaAc-Phe-OMe (3a), L-bpaAc-Lys(Z)-OMe (3b), and bpaAc-Gly-OEt (3c) were treated with Zn(OTf)2 (OTf = CF3SO3-) to yield the trigonal-bipyramidal complexes [(L-bpaAc-Phe-OMe)ZnOTf](OTf) (6a), [(L- bpaAc-Lys(Z)-OMe)ZnOTf](OTf) (6b), and [(bpaAc-Gly-OEt)ZnOTf](OTf) (6c). Crystal structures of 6c and the hydrolysis product [(L-bpaAc-Phe-OMe)- (H2O)ZnOTf](OTf)2 (7a) are reported. The results suggest the formation of a chiral pocket at the metal center provided by the benzyl substituent in the L-phenylalanine derivative 7a. This observation is further supported by 1H- NMR and circular dichroism spectroscopic data. These methods indicate a significant ordering effect within the ligands upon metal coordination as well as interactions between the first coordination spheres and their chiral environments provided by the L-phenylalanine and L-lysine moieties of 3a and 3b, respectively. Our results are discussed with respect to the development of chiral building blocks for transition metal catalysts and biomimetic assemblies.
