84152-32-9Relevant academic research and scientific papers
Modeling Tryptophan/Indoleamine 2,3-Dioxygenase with Heme Superoxide Mimics: Is Ferryl the Key Intermediate?
Mondal, Pritam,Wijeratne, Gayan B.
, p. 1846 - 1856 (2020)
Tryptophan oxidation in biology has been recently implicated in a vast array of paramount pathogenic conditions in humans, including multiple sclerosis, rheumatoid arthritis, type-I diabetes, and cancer. This 2,3-dioxygenative cleavage of the indole ring of tryptophan with dioxygen is mediated by two heme enzymes, tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO), during its conversion to N-formylkynurenine in the first and rate-limiting step of kynurenine pathway. Despite the pivotal significance of this enzymatic transformation, a vivid viewpoint of the precise mechanistic events is far from complete. A heme superoxide adduct is thought to be the active oxidant in both TDO and IDO, which, following O-O bond cleavage, presumably generates a key ferryl (FeIV=O) reaction intermediate. This study, for the first time in model chemistry, demonstrates the potential of synthetic heme superoxide adducts to mimic the bioinorganic chemistry of indole dioxygenation by TDO and IDO, challenging the widely accepted categorization of these metal adducts as weak oxidants. Herein, an electronically divergent series of ferric heme superoxo oxidants mediates the facile conversion of an array of indole substrates into their corresponding 2,3-dioxygenated products, while shedding light on an unequivocally occurring, putative ferryl intermediate. The oxygenated indole products have been isolated in a?31% yield, and characterized by LC-MS, 1H and 13C NMR, and FT-IR methodologies, as well as by 18O2(g) labeling experiments. Distinctly, the most electron-deficient superoxo adduct is observed to react the fastest, specifically with the most electron-rich indole substrate, underscoring the cruciality of electrophilicity of the heme superoxide moiety in facilitating the initial indole activation step. Comprehensive understanding of such mechanistic subtleties will benefit future attempts in the rational design of salient therapeutic agents, including next generation anticancer drug targets with amplified effectivity.
Resonance Raman Spectra of Ferrylporphyrins and Related Compounds in Dioxygen Matrices
Proniewicz, Leonard M.,Bajdor, Krzysztof,Nakamoto, Kazuo
, p. 1760 - 1766 (1986)
Resonance Raman (RR) spectra are reported for three ferryl compounds: (TPP)FeO, (OEP)FeO, and (salen)FeO (where TPP=tetraphenylporphyrinato anion, OEP=octaethylporphyrinato anion, and salen=N,N'-ethylenebis(salicylideneaminato) anion). (TPP)FeO and (OEP)FeO were formed via laser photolysis (406.7-nm line) of cocondensation products of Fe(TPP) and Fe(OEP), respectively, with dioxygen at 15 K.In both cases, the ferryl stretching (ν(FeO)) bands appear at 852 cm-1 as the O-O bond cleveage reaction proceeds and their intensities reach maxima after about 20 min of laser irradiation (1-2-mW power).This photolysis does not occur with other exciting lines.In the case of Fe(salen), similar photolysis occurs readily with laser lines in the range from 457.9 to 514.5 nm as evidenced by the appearance of the ν(FeO) at 851 cm-1.In contrast, attempts to prepare (Pc)FeO (Pc=phthalocyanato anion) by similar procedures were not successful although all lines in the region from 406.7 to 676.4 nm were employed.Instead, these excitations produced the RR spectrum of Fe(Pc)O2 which exhibited the ν(Fe-O2) and δ(FeOO) at 488 and 279 cm-1, respectively.The oxidation and/or spin state marker bands were observed at 1375 (band A), 392 (band E), and 1575 cm-1 (band D) for (TPP)FeO and at 1379 (ν4), 1507 (ν3), and 1643 cm-1 (ν10) for (OEP)FeO.These frequencies indicate that the iron atom in the ferrylporphyrins is low-spin with formal oxidation state close to Fe(IV).Furthermore, the FeO stretching force constant obtained (5.32 mdyn/Angstroem) is much larger than the FeO single-bond stretching force constant (3.80 mdyn/Angstroem).On the basis of these and other results, we proposed to formulate the five-coordinate ferrylporphyrin as PFeIVO(2-) (P=porphyrin) which involves one ? and two ? bonds.The marked enhancement of the ν(FeO) relative to porphyrin core vibrations suggest the possibility of direct resonance excitation via an electronic transition involving FeO charge transfer which is located near 406.7 nm, the wavelength of the laser line used for excitation.
Photochemical reduction of nitrate and nitrite by manganese and iron porphyrins
Suslick, Kenneth S.,Watson, Randall A.
, p. 912 - 919 (2008/10/08)
New nitrate and nitrite complexes of metalloporphyrins have been synthesized and crystallographically characterized, and their photochemistry has been examined. Irradiation of Mn(TPP)(NO3) and Mn(TPP)(NO2) (where TPP = 5,10,15,20-tetraphenylporphyrinate(2-)) produces the high-valent metal-oxo species O=MnIV(TPP) quantitatively, with quantum yields of 1.58 × 10-4 and 5.30 × 10-4, respectively. This metal-oxo species is capable of oxidizing substrates, as demonstrated in reactions with styrene or triphenylphosphine. Mn(TPP)(NO2) is formed as an intermediate in the complete photolysis of Mn(TPP)(NO3). Similarly, the photochemistry of Fe(TPP)(NO3) produces substrate oxidation, including C-H hydroxylation, which suggests the photochemical formation of O=FeIV(TPP.+) as the active oxidant. Remarkably, all three oxygen atoms of the initially bound NO3- can be used for substrate oxidation. The X-ray crystal structures of Mn(TPP)(NO3)·2C6H6 and Mn(TPP)(NO2)·C6H6 have been solved. In the nitrate complex Mn(TPP)(NO3), the average Mn-pyrrole N distance is 2.007 A?, with the metal 0.21 A? above the mean plane of the nitrogen atoms. The nitrate ion is coordinated in a unidentate fashion with a Mn-O bond length of 2.101 A?. Mn(TPP)(NO2) is the first metalloporphyrin complex with oxygen-bound nitrite. The average Mn-pyrrole nitrogen distance is 2.012 A?, with the metal 0.23 A? above the mean plane of the nitrogen atoms. The nitrite ion is coordinated through one of the oxygens, with a Mn-O bond length of 2.059 A?. Crystal data for Mn(TPP)(NO3)·2C6H6 at -76°C: space group P1, a = 13.271 (4) A?, b = 13.610 (5) A?, c = 12.880 (3) A?, α = 111.44 (2)°, β = 95.71 (2)°, γ = 85.50 (3)°, V = 2152 (2) A?3, Z = 2, RF = 0.063, RwF = 0.086 for 408 variables and 4890 unique data with I > 2.58σ(I). Crystal data for Mn(TPP)(NO2)·C6H6: space group Pccn, a = 21.631 (11) A?, b = 19.941 (12) A?, c = 17.991 (6) A?, V = 7760 (7) A?3, Z = 8, RF = 0.062, RwF = 0.096 for 543 variables and 3820 unique data with I > 2.58σ(I).
Picosecond Absorption Studies on the Excited State of (μ-Oxo)bis
Guest, C. R.,Straub, K. D.,Hutchinson, J. A.,Rentzepis, P. M.
, p. 5276 - 5280 (2007/10/02)
We have measured the kinetics and spectra of the intermediates of (μ-oxo)bis in various solvents.The spectra of the intermediate species were measured at various intervals of time from -100 to 4.3 ns after excitation with a 532- or 355-nm 25-ps pulse.The intermediate state, possibly a cation radical, was assigned to a monomer that forms the photodissociated pair TPPFeII+ + TPPFeIII-O- and yields a small amount of disproportionation reaction products, FeIITPP and TPPFeIV=O.t
MECHANISTIC CONSIDERATIONS IN THE PHOTODIPPROPORTIONATION OF μ-OXO-BIS ((TETRAPHENYLPORPHINATO)IRON(III))
Peterson, Mark W.,Rivers, David S.,Richman, Robert M.
, p. 2907 - 2915 (2007/10/02)
The photochemistry of μ-oxo-bis((tetraphenylporphinato)iron(III)) has been studied.Both continuous and photolysis establish a photochemical disproportionation to fom the ferrous complex FeTPP and the ferryl complex FeOTTP: Using triphenylphosp
