Limits...
Biomimetic modeling of copper complexes: a study of enantioselective catalytic oxidation on d-(+)-catechin and L-( - )-epicatechin with copper complexes.

Mutti FG, Pievo R, Sgobba M, Gullotti M, Santagostini L - Bioinorg Chem Appl (2008)

Bottom Line: The unstable quinones were trapped by the nucleophilic reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH), and have been calculated the molar absorptivities of the different quinones.The catalytic efficiency is moderate, as inferred by kinetic constants, but the complexes exhibit significant enantio-differentiating ability towards the catechols, albeit for the dinuclear complexes, this enantio-differentiating ability is lower.In all cases, the preferred enantiomeric substrate is D-(+)-catechin to respect the other catechol, because of the spatial disposition of this substrate.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Chimica Inorganica, Metallorganica e Analitica "Lamberto Malatesta", Università di Milano, Istituto ISTM-CNR, Via Venezian 21, 20133 Milano, Italy.

ABSTRACT
The biomimetic catalytic oxidations of the dinuclear and trinuclear copper(II) complexes versus two catechols, namely, D-(+)-catechin and L-( - )-epicatechin to give the corresponding quinones are reported. The unstable quinones were trapped by the nucleophilic reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH), and have been calculated the molar absorptivities of the different quinones. The catalytic efficiency is moderate, as inferred by kinetic constants, but the complexes exhibit significant enantio-differentiating ability towards the catechols, albeit for the dinuclear complexes, this enantio-differentiating ability is lower. In all cases, the preferred enantiomeric substrate is D-(+)-catechin to respect the other catechol, because of the spatial disposition of this substrate.

No MeSH data available.


Proposed structuresfor the trinuclear copper(II) complexes (I) and for the putative intermediateadducts (II) with the catechins.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2553160&req=5

sch3: Proposed structuresfor the trinuclear copper(II) complexes (I) and for the putative intermediateadducts (II) with the catechins.

Mentions: Asreported in the previous papers [26, 27], the trinuclear complexes display astructure in which the Cu(II) center at B site and one of the two centers at Asite are mediated by a double hydroxide bridge (Scheme 3, Structure I). In thiscase, the chiral recognition could depend not only on steric interactions butalso by coordination of the free aliphatic hydroxide to the other Cu(II): a site(Scheme 3, Structure II) that allows a significant enantio-differentiatingbehavior towards optically active substrates. In fact, considering thethree-dimensional structures of the two catechins reported before in Figure 3,one notices that the aliphatic hydroxide, in the D-(+)-catechin,is opposite to the two catecholic groups, and therefore able to coordinate atthe Cu(II) center at A site. The L-(–)-epicatechinshows the aliphatic hydroxide too far from the Cu(II) center at A site and, inthis case, the interaction needs a modification of the structure of thecomplexes with a strong tension of the ligands.


Biomimetic modeling of copper complexes: a study of enantioselective catalytic oxidation on d-(+)-catechin and L-( - )-epicatechin with copper complexes.

Mutti FG, Pievo R, Sgobba M, Gullotti M, Santagostini L - Bioinorg Chem Appl (2008)

Proposed structuresfor the trinuclear copper(II) complexes (I) and for the putative intermediateadducts (II) with the catechins.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2553160&req=5

sch3: Proposed structuresfor the trinuclear copper(II) complexes (I) and for the putative intermediateadducts (II) with the catechins.
Mentions: Asreported in the previous papers [26, 27], the trinuclear complexes display astructure in which the Cu(II) center at B site and one of the two centers at Asite are mediated by a double hydroxide bridge (Scheme 3, Structure I). In thiscase, the chiral recognition could depend not only on steric interactions butalso by coordination of the free aliphatic hydroxide to the other Cu(II): a site(Scheme 3, Structure II) that allows a significant enantio-differentiatingbehavior towards optically active substrates. In fact, considering thethree-dimensional structures of the two catechins reported before in Figure 3,one notices that the aliphatic hydroxide, in the D-(+)-catechin,is opposite to the two catecholic groups, and therefore able to coordinate atthe Cu(II) center at A site. The L-(–)-epicatechinshows the aliphatic hydroxide too far from the Cu(II) center at A site and, inthis case, the interaction needs a modification of the structure of thecomplexes with a strong tension of the ligands.

Bottom Line: The unstable quinones were trapped by the nucleophilic reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH), and have been calculated the molar absorptivities of the different quinones.The catalytic efficiency is moderate, as inferred by kinetic constants, but the complexes exhibit significant enantio-differentiating ability towards the catechols, albeit for the dinuclear complexes, this enantio-differentiating ability is lower.In all cases, the preferred enantiomeric substrate is D-(+)-catechin to respect the other catechol, because of the spatial disposition of this substrate.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Chimica Inorganica, Metallorganica e Analitica "Lamberto Malatesta", Università di Milano, Istituto ISTM-CNR, Via Venezian 21, 20133 Milano, Italy.

ABSTRACT
The biomimetic catalytic oxidations of the dinuclear and trinuclear copper(II) complexes versus two catechols, namely, D-(+)-catechin and L-( - )-epicatechin to give the corresponding quinones are reported. The unstable quinones were trapped by the nucleophilic reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH), and have been calculated the molar absorptivities of the different quinones. The catalytic efficiency is moderate, as inferred by kinetic constants, but the complexes exhibit significant enantio-differentiating ability towards the catechols, albeit for the dinuclear complexes, this enantio-differentiating ability is lower. In all cases, the preferred enantiomeric substrate is D-(+)-catechin to respect the other catechol, because of the spatial disposition of this substrate.

No MeSH data available.