Aminopeptidase function of dinuclear zinc(II) complexes with chiral dinucleating ligands: Stereoselectivity by chiral substrate recognition

The aminopeptidase functions of newly obtained chiral dinuclear zinc(II) complexes [Zn2(R-bppmp)(MeCO2)2]BPh4 (1R) and [Zn2(S-bppmp)(MeCO2)2]BPh4 (1S) were estimated using l-leucine-p-nitroanilide as a substrate [H(R/S-bppmp): 2,6-bis[{(R/S)-1-phenylethyl-2-pyridylmethyl}aminomethyl]-4-methylphenol]. Both complexes showed aminopeptidase activity, and a second-order rate equation was obtained as v = k [complex][substrate]. The rate constants k were 3.3(7) × 10−2 for 1R, and 7.6(5) × 10−2 dm3 mol−1 s−1 for 1S in a mixture of 40% DMF and 60% aqueous solution at pH 8.0, and the activity for 1S was 2.3 times greater than that for 1R. Molecular mechanics calculation indicated that 1S is very suitable for substrate incorporation.