Jacek Wojaczyński

Enantioselective Synthesis of Sulfoxides: 2000−2009

1.2.2. Davis Oxaziridines 4305 1.2.3. Metal Complexes in Enantioselective Oxidation 4305 1.3. New Applications 4307 1.3.1. Chiral Sulfinate Method 4307 1.3.2. Oxidation with Chiral Oxaziridines 4309 1.3.3. Oxidation Using Metal Complexes 4310 1.4. New Systems 4313 1.4.1. C-S Bond Formation 4314 1.4.2. Organic Oxidants 4315 1.4.3. Oxidations Catalyzed by Metal Complexes 4316 1.5. Diastereoselective Oxidations 4330 1.6. Heterogenized Systems 4332 1.7. Summary 4335 2. Biological Oxidations 4336 2.

Poly- and oligometalloporphyrins associated through coordination

Abstract Significant developments in the construction of oligoporphyrins and oligometalloporphyrins supply a large variety of new interesting compounds with potential use in electron and energy transfer. Their physicochemical properties depend primarily on the nature of the linkage between porphyrin building blocks. In this review we have focused on the expanding role of the coordination bond in creation of polyporphyrin architecture.

Heme environment in HmuY, the heme-binding protein of Porphyromonas gingivalis

Porphyromonas gingivalis, a Gram-negative anaerobic bacterium implicated in the development and progression of chronic periodontitis, acquires heme for growth by a novel mechanism composed of HmuY and HmuR proteins. The aim of this study was to characterize the nature of heme binding to HmuY. The protein was expressed, purified and detailed investigations using UV-vis absorption, CD, MCD, and (1)H NMR spectroscopy were carried out. Ferric heme bound to HmuY may be reduced by sodium dithionite and re-oxidized by potassium ferricyanide. Heme complexed to HmuY, with a midpoint potential of 136mV, is in a low-spin Fe(III) hexa-coordinate environment. Analysis of heme binding to several single and double HmuY mutants with the methionine, histidine, cysteine, or tyrosine residues replaced by an alanine residue identified histidines 134 and 166 as potential heme ligands.

Iron(III) mesoporphyrin IX and iron(III) deuteroporphyrin IX bind to the Porphyromonas gingivalis HmuY hemophore

Porphyromonas gingivalis acquires heme through an outer-membrane heme transporter HmuR and heme-binding hemophore-like lipoprotein HmuY. Here, we compare binding of iron(III) mesoporphyrin IX (mesoheme) and iron(III) deuteroporphyrin IX (deuteroheme) to HmuY with that of iron(III) protoporphyrin IX (protoheme) and protoporphyrin IX (PPIX) using spectroscopic methods. In contrast to PPIX, mesoheme and deuteroheme enter the HmuY heme cavity and are coordinated by His134 and His166 residues in a fully analogous way to protoheme binding. However, in the case of deuteroheme two forms of HmuY-iron porphyrin complex were observed differing by a 180° rotation of porphyrin about the α-γ-meso-carbon axis. Since the use of porphyrins either as active photosensitizers or in combination with antibiotics may have therapeutic value for controlling bacterial growth in vivo, it is important to compare the binding of heme derivatives to HmuY.

Oxophlorin and Metallooxophlorin Radicals—DFT Studies

A flexible oxophlorin macrocycle, which allows the location of labile hydrogen atoms alternatively at the pyrrole nitrogen, oxygen, or meso-carbon atoms, has been studied by density functional theory (DFT). DFT calculations were carried out on oxophlorin 1, 5-hydroxyporphyrin 2, and two isomers of oxophlorin 3 and 4 (the proton added at the tetrahedral C(15) or the C(10) meso-carbon, respectively). The oxophlorin-hydroxyporphyrin structural changes are appropriately reflected by the significant changes of the meso carbon-oxygen bond lengths, which are in the limits of typical C=O and C-O distances. The rearrangement that creates the iso-oxophlorin macrocycle 3 (4) results in near tetrahedral geometry around the C(15) (C(10)) carbon atom, with the C(14)-C(15) and C(15)-C(16) (C(9)-C(10) and C(10)-C(11)) bond lengths corresponding to a single C-C bond. 5-Hydroxyporphyrin 2 is aromatic and has a bond pattern resembling that of regular porphyrin. In 1, 3, and 4, a localization of single and double bonds was seen, which agrees with the nonaromatic nature of oxophlorin, or isooxophlorin. The relative stability decreases in the order: 2 (0) > 3 (4.85) > 1 (5.11) > 4 (10.04) > 3-cis (12.89) (the number in parentheses is the relative energy, in kcal mol-1). The energy difference between the NH-cis and NH-trans tautomers, which is 8.04 kcal mol-1 for 3, results from a destabilizing NH-NH cis-interaction. DFT calculations were performed on the oxophlorin dianion radical (OP.)2- and a series of metallooxophlorin radicals ([(OP.)LiI]-, [(OP.)ZnII], [(OP.)GaIII]+, and (OP.)GaIIIF, in order to assess their electronic structures. Typically, the largest atomic spin density was found at the C(10) (C(20)) and C(15) meso positions, with the spin density at C(15) being twice as large as that at C(10). The spin density at the C(5) atom is negligible. A large spin density was found at the O(5) oxygen atom. The amount of spin density at the meso positions decreased as the cationic charge increased. When considering the absolute values of the spin densities, the opposite trend was observed at the pyrrolic carbon atoms. The spin density at the nucleus (Fermi contact terms) has also been analyzed. The spin distributions of iron oxophlorins determined by NMR were attributed to an oxophlorin radical electronic structure. The calculated spin density maps accounted for the essential NMR spectroscopic features of important intermediates in the heme degradation process--iron oxophlorin complexes. The DFT calculations reproduced the following spectroscopic patterns: a) |delta H(15)|>|delta H(10)|>>|delta (beta-H)|, b) a sign alteration of the contact shifts for identical substituents located on the same pyrrole ring.

Novel routes for the modification of iron porphyrins

Abstract The effects of unconventional modifications of iron tetraarylporphyrins on their electronic structure and chemical properties were examined. The alterations included the β( meso )-substitution or an oxygen atom insertion into an iron–nitrogen bond. The profound transformation of porphyrin to 2-pyridiniumylporphyrin, isoporphyrin or porphodimethene occurred in reactions involving iron porphyrin in highly-oxidized states and pyridine. Addition of 2,4,6-collidine generated iron porphyrin N-oxides. The 2-hydroxy substituted tetraphenylporphyrin (a hybrid-type ligand) coordinates using a tetranitrogen macrocyclic center and an ionized hydroxy group of the periphery to form the cyclic trimer [(2-O–TPP)Fe(III)] 3 . The seven pyrrole protons of (2-X-TPP)Fe(III)Cl and [(2-X–TPP)Fe(III)(CN) 2 ] provided the direct probe of the spin density distribution around the porphyrin macrocycle as determined by 1 H-NMR. Studies on the controlled modification of the tetraarylporphyrin periphery also included a symmetrical modification of a single pyrrole ring to obtain iron(III) quinoxalinoporphyrin characterized by the less common (d xz d yz ) 4 (d xy ) 1 low-spin ground electronic state of the bis-cyanide derivative [(QTPP)Fe(III)(CN) 2 ] − .

Common origin, common fate: regular porphyrin and N-confused porphyrin yield an identical tetrapyrrolic degradation product.

The formation of an identical linear tetrapyrrole observed in the course of photooxidation of meso-tetraarylporphyrin and its N-confused isomer can be explained as a result of 1,2- and 1,3-dioxygen addition, respectively, as substantiated by DFT calculations.

Dipyrrin-Bis(N-Confused Porphyrin) Conjugate: Synthesis, Synergetic Ligation and Chirality Sensing

A fully conjugated system 4 consisting of two 2-aza-21-carbaporphyrin (NCP) subunits bridged by dipyrrin was synthesized by a highly selective condensation of 3-pyrrole-NCP 2 with aryl aldehydes. The free base 4 as well as its silver(III) complex 5 exhibited flexibility of the bridge allowing synergetic binding of AgI , thus leading to a mixed-valence tetraporphyrinic assembly consisting of eight silver atoms which was characterized both in the solid state and in solution. Binding of chiral acid by 4 and 5 was shown by observation of an induced optical activity of the adducts.

Zinc complexes formed by 2,2′-bipyridine and 1,10-phenanthroline moieties combined with 2-azanorbornane: modular chiral catalysts for aldol reactions

Chiral scaffolds of 2-azabicyclo[2.2.1]heptane and 2-azabicyclo[3.2.1]octane were used for the construction of new modular catalysts containing complexing moieties pyridine, 2,2′-bipyridine and 1,10-phenanthroline appended by an imine linkage. The coordination abilities of the new ligands towards Zn(II) were investigated using NMR and UV spectroscopy. The plausible structures of the [ZnL2]2+ and [ZnLXn](2−n)+ complexes formed were established by comparison of the experimental and DFT-calculated NMR spectra. The catalytic application of the [ZnLXn](2−n)+-type complexes in the asymmetric aldol reaction of ketones with aromatic aldehydes produced an excess of the respective syn-aldols in up to >98% ee.

Degradation Pathways for Porphyrinoids

Porphyrin, a tetrapyrrolic aromatic macrocycle, is relatively resistant to degradation. However, certain strong oxidants (e.g. chromic acid) cause its decomposition to monopyrrolic units. More often, ring opening caused by attack of oxidant on a meso-position has been observed. Such degradation by metal salts (thallium(III), cerium(IV)), nitric acid, and other reagents has been studied. Light-driven macrocycle opening by dioxygen has also been noted. Coupled oxidation of metalloporphyrins has been investigated mainly as a mimics of heme degradation observed in vivo.