The Role of Dioxygen Species in the Base‐ and Cobalt‐catalyzed Oxygenation of Hindered Phenols

Nishinaga, Akira; Itahara, Toshio; Shimizu, Tadashi; Tomita, Hiroya; Nishizawa, Kanji; Matsuura, Teruo

doi:10.1111/j.1751-1097.1978.tb06999.x

Cited by 12 publications

(2 citation statements)

References 31 publications

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“…It should be emphasized that the tanning reaction described herein involves an aminophenol and not a catechol and that, as yet, no aminophenols have been implicated in the tanning of insect cuticle. However, the similar chemical reactivities ofcatechols and o-aminophenols (24,25) suggest that analogous adducts may well be formed from tyrosine residues that have been exposed to oxidized catechols. It is of interest that cuticle proteins are often rich in tyrosine and that these aromatic regions have been proposed to serve as initiation centers for cross-linking (26).…”

Section: Discussionmentioning

confidence: 99%

Involvement of tyrosine residues in the tanning of proteins by 3-hydroxyanthranilic acid.

Manthey

Pyne

Truscott

1992

Proc. Natl. Acad. Sci. U.S.A.

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The binding of oxidized phenolic compounds to proteins is of importance in a number of biological systems, including the sclerotization of insect cuticle and the tanning of cocoons. 3-Hydroxyanthranilic acid (3HAA), an aminophenol, is a tryptophan metabolite that undergoes autoxidation readily, and proteins incubated in the presence of 3HAA and oxygen become colored and oxidized. Some moth species are thought to employ this reactivity of 3HAA with proteins for the tanning of cocoons, but the detailed mechanism of this process has not been studied previously. We show that one reaction pathway involves the covalent coupling of 3HAA with tyrosine to form a benzocoumarin derivative, a dibenzo[bdJpyran-6-one. The stability of the benzocoumarin to conditions of acid hydrolysis normally used for protein digestion has enabled the isolation of the tyrosine adduct from bovine serum albumin that had been incubated with 3HAA. The adduct was also isolated from cocoons of Samia cynthia and Hyalophora gloveri, two species of moths reported to utilize 3HAA for cocoon tanning. These findings indicate that one mechanism of interaction of 3HAA with proteins involves a radical-radical coupling with tyrosine residues.Phenolic compounds and their quinonoid (1) oxidation products are widespread in nature. As discussed in a comprehensive review of these reactions (1), the biological activity of many quinonoids consists ultimately in the chemical modification of biopolymers. Aside from their role as defensive secondary metabolites in, for example, fungi, plants, and marine organisms (2,3), the interaction of quinonoid compounds with proteins is important in melanoprotein synthesis in animals and sclerotin formation in insects.Indeed, many stages in the life cycle of insects are dependent on such reactions taking place. The sclerotization (hardening) of the insect cuticle, for instance, with the consequent formation of a rigid yet light exoskeleton confers both protection and the potential for flight to these arthropods. A common feature of cuticle sclerotization, cocoon tanning, and ootheca (egg case) hardening is the modification of structural proteins by phenolic chemicals that have been rendered reactive as a result of enzymic oxidation (4). Most commonly, substituted o-or p-hydroxyphenols are employed, but the use of o-aminophenols such as 3-hydroxyanthranilic acid (3HAA) has also been reported: for example, the North American robin moth (Hyalophera gloveri) and the Indian Tree of Heaven silkmoth (Samia cynthia) use 3HAA for cocoon tanning (5).In the present work we have explored the interaction of 3HAA with proteins under oxidizing conditions. We have demonstrated that covalent binding of 3HAA to tyrosine residues of proteins occurs under oxidizing conditions with the formation of a benzocoumarin derivative. This benzocoumarin was also isolated from cocoon proteins of H. gloveri and S. cynthia. These data indicate that free radical reactions involving the tyrosine residues of proteins occur during the tanning process. MATER...

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Section: Discussionmentioning

confidence: 99%

Involvement of tyrosine residues in the tanning of proteins by 3-hydroxyanthranilic acid.

Manthey

Pyne

Truscott

1992

Proc. Natl. Acad. Sci. U.S.A.

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“…These studies implicated H-atom abstraction by a Cosuperoxo intermediate as the key step that initiates phenol oxidation. [13][14][15][16][17][18][19][20][21] However, the latter studies often involved observations made under catalytic conditions, and did not examine well-characterized Co(O 2 •−) species in direct reaction with H-atom donors. Recently, the isolated H-atom abstraction step has been studied in detail with well-defined iron and cobalt superoxo species.…”

Section: Introductionmentioning

confidence: 99%

A Nonheme Thiolate-Ligated Cobalt Superoxo Complex: Synthesis and Spectroscopic Characterization, Computational Studies, and Hydrogen Atom Abstraction Reactivity

et al. 2019

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The synthesis and characterization of a Co(II) dithiolato complex Co(M e3 TACN)(S 2 SiMe 2 ) (1) is reported. Reaction of 1 with O 2 generates a rare thiolate-ligated cobalt-superoxo species Co(O 2 ) (M e3 TACN)(S 2 SiMe 2 ) (2) that was characterized spectroscopically and structurally by resonance Raman, EPR, and X-ray absorption spectroscopies as well as density functional theory (DFT). Metal-superoxo species are proposed to S-oxygenate metal-bound thiolate donors in nonheme thiol dioxygenases, but 2 does not lead to S-oxygenation of the intramolecular thiolate donors, and does not react with exogenous sulfur donors. However, complex 2 is capable of oxidizing the O-H bonds of 2,2,6,6-tetramethylpiperidin-1-ol (TEMPOH) derivatives via H-atom abstraction. Complementary proton-coupled electron-transfer (PCET) reactivity is seen for 2 with separated proton/reductant pairs. The reactivity studies indicate that 2 can abstract H-atoms from weak X-H bonds with BDFE ≤ 70 kcal mol-1. DFT calculations predict that the putative Co(OOH) product has an O-H bond dissociation free energy (BDFE) = 67 kcal mol −1 , which matches the observed pattern of reactivity seen for 2. These data provide new information regarding the selectivity of Soxygenation versus H-atom abstraction in thiolate-ligated nonheme metalloenzymes that react with O 2 .

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Organic reactions involving the superoxide anion

Frimer

1983

PATAI'S Chemistry of Functional Groups

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The Role of Dioxygen Species in the Base‐ and Cobalt‐catalyzed Oxygenation of Hindered Phenols

Cited by 12 publications

References 31 publications

Involvement of tyrosine residues in the tanning of proteins by 3-hydroxyanthranilic acid.

Involvement of tyrosine residues in the tanning of proteins by 3-hydroxyanthranilic acid.

A Nonheme Thiolate-Ligated Cobalt Superoxo Complex: Synthesis and Spectroscopic Characterization, Computational Studies, and Hydrogen Atom Abstraction Reactivity

Organic reactions involving the superoxide anion

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