Copper(Ⅱ)-Hydroperoxo Complex Induced Oxidative N-Dealkylation Chemistry

摘要

In this report, we describe the generation of a new hydroperoxo-copper(Ⅱ) mononuclear complex which effects oxidative N-dealkylation chemistry on a substrate which is juxtaposed to the reacting Cu~Ⅱ(~-OOH) moiety. The interest in such an investigation derives from copper bioinorganic chemistry: (a) There remain fundamental questions concerning the inherent coordination structures and reactivity of single-copper complexes bound to dioxygen and its reduced derivatives, such as superoxide (O_2~-), peroxide (O_2~(2-)), or hydroperoxide (~-OOH). (b) Structurally similar peptidylglycine-α-hydroxylating monooxygenase (PHM) and dopamine β-monooxygenase (DβM) effect related substrate hydroxylation reactions at a mononuclear copper center. A Cu~Ⅱ(~-OOH) moiety was previously implicated as the active species formed prior to DβM or PHM substrate H-atom abstraction. More recent experimental and computational chemistries have, however, brought attention to a Cu~Ⅰ/O_2-derived superoxo Cu~Ⅱ(O_2~-) moiety as the likely H-atom abstracting agent. Still other theoretical treatments prefer a prior (rather then subsequent) O-O cleavage from Cu~Ⅱ(~-OOH) leading to a high-valent [Cu-O]~(2+) or [Cu-O]~(+9) moiety which effects H-atom transfer. As applied to PHM, the methylene H-atom abstraction from and subsequent rebound to the (peptide)C(O)-NHCH_2COOH substrate would give hydroxylated (peptide)C(O)-NHCH(OH)-COOH; this subsequently transforms to amine (here carboxamide) (peptide)C(O)NH_2 and aldehyde HC(O)COOH products. Our results presented here suggest that a Cu~Ⅱ(~-OOH) species or a product derived from this merits further serious attention in discussions of enzyme mechanism or applications to practical chemistry.