Cytochrome P450 Catalyzed Oxidative Hydroxylation of Achiral Organic Compounds with Simultaneous Creation of Two Chirality Centers in a Single CH Activation Step

Regio‐ and stereoselective oxidative hydroxylation of achiral or chiral organic compounds mediated by synthetic reagents, catalysts, or enzymes generally leads to the formation of one new chiral center that appears in the respective enantiomeric or diastereomeric alcohols. By contrast, when subjecting appropriate achiral compounds to this type of C? H activation, the simultaneous creation of two chiral centers with a defined relative and absolute configuration may result, provided that control of the regio‐, diastereo‐, and enantioselectivity is ensured. The present study demonstrates that such control is possible by using wild type or mutant forms of the monooxygenase cytochrome P450 BM3 as catalysts in the oxidative hydroxylation of methylcyclohexane and seven other monosubstituted cyclohexane derivatives.     

Electrochemically Generated Nanoparticles of Halogen‐Bridged Mixed‐Valence Binuclear Metal Complex Chains

Spherical nanoparticles composed of MMX chains can be made by a polymerization strategy driven by electrochemical processes. In particular, the [Pt₂(MeCS₂)₄I₂] (MMI₂) dimetal subunit is employed as a monomer for the formation of [Pt₂(MeCS₂)₄I]_n spherical nanostructures on surfaces. We have paid particular attention to elucidating the general mechanism of the deposition process on the basis of in situ electrochemical measurements. The reduction of MMI₂ to give the electrodeposition of nanostructures agrees well with formation of the reduced [MMI₂]^? species followed by a disproportionation mechanism mediated by iodide anions. The chemical composition of the particles was determined by energy‐dispersive X‐ray spectroscopy (EDX) and X‐ray photoelectron spectroscopy (XPS) to reveal the MMI₂ polymer.     

Highly Enantioselective Construction of Tricyclic Derivatives by the Desymmetrization of Cyclohexadienones

The asymmetric synthesis of tricyclic compounds by the desymmetrization of cyclohexadienones is presented. The reaction tolerated a large variety of substituents at different positions of the cyclohexadienone, and heterocyclic rings of different sizes were accessible. Density functional theory calculations showed that the reaction proceeds through an asynchronous [4+2] cycloaddition.     

Electrically forced coaxial nanojets for one-step hollow nanofiber design

The outer liquid of a two-liquid coaxial electrified jet is gelled before the onset of natural instabilities to yield hollow nanofibers. By using sol-gel chemistry, innocuous solvents such as glycerol and olive oil, and electrohydrodynamics, it is possible to make such structures in a rather straightforward manner.     

A 1:1.5 complex of 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane and 2,6-dihydoxyanthraquinone

A complex of 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane (dioxocyclam) and 2,6-dihydoxyanthraquinone (anthraflavic acid) has been obtained. The complex (crystals grown from water-ethanol solution) has a stoichiometry dioxocyclam-anthraflavic acid 1:1:5. C₃₁H₃₂N₄O₈, chemical formula weight 588.61, triclinic, P – 1, a = 10.542(3) Å, b = 11.936(2) Å, c = 12.206(2) Å, = 104.00(1)°, = 92.68(2)°, = 103.64(2)°, V = 1439.4 (5) ų, Z = 2, D_x = 1.358 g cm^–3. Only one of the two amine N-atoms of the macrocycle is protonated due to very weak acidic properties of 2,6-dihydoxyanthraquinone. Due to the rather poor quality of the crystals and structure refinement, reliable determination of H-bonds is complicated. Nevertheless, several types of H-bonding responsible for the formation of a developed supramolecular network can be suggested: between the protonated amino groups and macrocycle's C=O moieties; between non-protonated amino groups and macrocycle's C=O moieties; between protonated and non-protonated amino groups; between the amide NH and C=O groups of anthraflavic acid; and between protonated and deprotonated hydroxy groups of the acid. Two types of anthraflavic components can be distinguished in the lattice: those having a parallel orientation with respect to the macrocyclic fragments and forming hydrogen bonds with the latter, and those lying in an approximately perpendicular plane and not involved in H-bonding with the macrocycles.     

Evidence of Native Metal–S2−–Metallothionein Complexes Confirmed by the Analysis of Cup1 Divalent‐Metal‐Ion Binding Properties

It has previously been shown that recombinant synthesis, under metal‐supplemented conditions, of diverse metallothioneins (MTs) results in the recovery of a subpopulation of S^2?‐containing complexes in addition to the S^2?‐devoid canonical metal–MT species. Further significance of this finding has remained veiled by the possibility of it being a mere consequence of synthesis in a heterologous bacterial system. Herein, we present definitive evidence that S^2? ligands are also constituents of native metal–MT complexes. Because, although practically universal, the highest S^2? content is incorporated by copper‐thioneins when coordinating divalent metal ions, we adapted the Saccharomyces cerevisiae Cup1 protein, which is the most paradigmatic copper‐thionein, as an experimental model. Most significantly, native Cd–Cup1 complexes were purified and fully spectroscopically and spectrometrically characterized from the 301N mutant yeast strain, which allows Cup1 synthesis even in the absence of copper. These results undoubtedly revealed the presence of a Cd–S^2?–Cup1 species in native preparations, which were only recovered when carefully avoiding the use of ion‐exchange chromatography in the purification protocol. Furthermore, complete analysis of recombinant (Escherichia coli) Zn–Cup1, Cd–Cup1, and Cu–Cup1 and those complexes that result from Zn/Cd and Zn/Cu replacements in vitro and acidification/renaturalization processes yielded a comprehensive and comparative overview of the metal‐binding abilities of Cup1. Overall, we consider the main conclusions of this study to go beyond the mere study of the particular Cup1 MT, so that they should be considered to delineate a new point of view on the interaction between copper‐thioneins and divalent metal ions, still an unexplored aspect in MT research.     

The electronic origin of unusually large nJFN coupling constants in some fluoroximes

SOPPA(CCSD) calculations show that the FC term is the most important contribution to the through‐space transmission of J_FN coupling constants for the fluoroximes studied in this work. Because of the well‐known behavior of FC term, a new rationalization for the experimental ^TSJ_FN SSCC is presented. It is mainly based on the overlap matrix (S_ij) between fluorine and nitrogen lone pairs obtained from NBO analyses. An expression is proposed to take into account the influence of the electronic density (D_ij) between coupled nuclei as well as the s% character at the site of the coupling nuclei of bonds and non‐bonding electron pairs involved in D_ij. In using this approach, a linear correlation between ^TSJ_FN versus D_ij is obtained. The most important aspect of this rationalization is related to the facility for understanding the behavior of some unusual experimental coupling constants. It is shown that, at least in this case, the electronic origin of the so‐called through‐space coupling is transmitted through to the overlap of orbitals on the coupled atoms, suggesting that, at least for these compounds, instead of through‐space coupling, it should better be dubbed as ‘through overlapping orbital coupling’. Copyright © 2013 John Wiley & Sons, Ltd.