Photosensitized oxygenation of Nb-methyltryptamine

Nakagawa, Masako; Yoshikawa, Kensei; Hino, Tohru

doi:10.1021/ja00855a035

Cited by 51 publications

(26 citation statements)

References 11 publications

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“…In accord with the general mechanism of oxidations of enamines (16), of which indoles are a special case (3), the 3-hydroperoxyindolenine 2 (17) was postulated to be the primary intermediate capable of rearranging to formylkynurenine (4), whether via an energetically unfavorable dioxetane 3 (18) or via hydrated intermediates 5 and/or 6 (19,20) may be left open at this point. Our recent studies on the dye-sensitized oxygenation of N(b)-methoxycarbonyltryptamine and -DL-tryptophan methyl ester [9; N(b) is the basic nitrogen, and N(a) is the indolic one] have provided unambiguous evidence for the intermediary formation of a 3-hydroperoxyindolenine (4,(21)(22)(23)(24). Furthermore, we have found a new reaction pathway to kynurenine via the long-sought-after 3a-hydroperoxyhexahydropyrroloindole (23,24).…”

mentioning

confidence: 76%

A valid model for the mechanism of oxidation of tryptophan to formylkynurenine—25 years later

Nakagawa

Watanabe

Kodato

et al. 1977

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

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104

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The dye-sensitized photooxygenation of DLtryptophan in aqueous solution leads to the tricyclic compound 2-carboxy-3a-hydroperoxy-1, 2,3,3a,8,8a-hexahydropyrrolo[2,3-blindole which, on reduction with dimethyl sulfide, furnishes two diastereoisomeric alcohols separable by fractional crystallization into a higher melting (mp 254°-256°) and a lower melting (mp 2280) diastereoisomer. Each of these alcohols was correlated with one of the analogous pair of isomeric 1,2-dicarbomethoxy analogs by alkaline hydrolysis and by x-ray analysis. In this way, the 3a-hydroxy-1,2-dimethoxycarbonyl-1, 2,3,3a,8,8a-hexahydropyrrolo[2,3-blindole, mp 163°-164°, was shown to have the trans configuration with regard to the relative positions of the hydroxyl and carbomethoxy groups and that, on alkaline hydrolysis, it produced the isomer with mp 2280, which therefore also has the trans configuration. The mechanism of the smooth thermal rearrangement of the (presumably ring-chain tautomeric) tryptophan hydroperoxy intermediates to formylkynurenine is discussed with its implications for the biological oxidation by tryptophan 2,3-dioxygenase. The first direct chemical conversion of tryptophan (1) to formylkynurenine (4) was by ozonolysis (1). The biochemical degradation of L-tryptophan by L-tryptophan oxygenase, a dioxygenase [L-tryptophan:oxygen 2,3-oxidoreductase (decyclizing), EC 1.13.11.11], served as one of the first demonstrations of the incorporation of both 180 moieties of molecular oxygen (1802) (2) and prompted many model studies involving intermediary hydroperoxides arising from indole substrates through. catalytic oxidation (3) or photooxygenation (4, 5).(See structure cut on top of next page.) Earlier studies (6-13; for reviews, see refs. 14 and 15) on the sensitized photooxygenation of 1 led to complicated mixtures of products in which kynurenine was detected (7) and formylkynurenine was isolated in low yield (12). In accord with the general mechanism of oxidations of enamines (16) 3-hydroperoxyindolenine (4, 21-24). Furthermore, we have found a new reaction pathway to kynurenine via the long-sought-after 3a-hydroperoxyhexahydropyrroloindole (23, 24).The reinvestigation of the dye-sensitized photooxygenation of tryptophan itself in aqueous solution has now led to the major product, 3a-hydroperoxypyrrolidinoindole (7) which easily rearranges to formylkynurenine (4) upon warming. EXPERIMENTALWhen an aqueous solution (300 ml) of DL-tryptophan (1) (1 g, 5 mmol) containing EtOH (15 ml) and Rose Bengal (0.4 mmol) was photooxygenated at 0°-5°for 2.5 hr, followed by reduction with dimethyl sulfide, the 3a-hydroxyhexahydropyrroloindole (8) was obtained as a mixture of two diastereoisomers that were readily separated by fractional crystallization from water to give 8a, mp 254°-256°(28%) and 8b, mp 2280 (28%), in addition to 23% of recovered tryptophan (1). The spectral properties of 8 were in complete accord with those reported by Savige (25) who obtained 8 by oxidation of 1 with peracetic acid. Neither formylkynurenine no...

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mentioning

confidence: 76%

A valid model for the mechanism of oxidation of tryptophan to formylkynurenine—25 years later

Nakagawa

Watanabe

Kodato

et al. 1977

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

Self Cite

104

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“…Tested compounds were dissolved in 20 mM NaPB (pH 7.4), and then exposed to light (30000 lux) for 0 -24 h. singlet oxygen gives both N-formylkynurenine and 3α-hydroxypyrroloindoles. 24,25 It is known that N-formylkynurenine and kynurenine are significant photosensitizing agents and much better singlet oxygen generators than Trp itself. 26 Thus, in this investigation, the excessive singlet oxygen might be produced from N-formylkynurenine and kynurenine, and subsequently enhance the photodegradation of Trp.…”

Section: Ros-mediated Photodegradation Of Trpmentioning

confidence: 99%

Photoreactivity of Amino Acids: Tryptophan-induced Photochemical Events via Reactive Oxygen Species Generation

2007

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ChemicalsEssential amino acids, quinine, sodium dodecyl sulfate (SDS), and several ROS scavengers, such as butylated hydroxyanisole (BHA), reduced gluthatione (GSH), sodium azide (NaN3), and Tryptophan (Trp), an aromatic amino acid, is a constituent of peptides/proteins and is also a precursor of serotonin, kynurenine derivatives, and nicotinamide adenine dinucleotides. There have been a number of reports on photochemical reactions involving peptides/proteins which contain Trp that showed significant photodegradation, dimerization, and photoionization. The photochemical properties of Trp have not been fully elucidated, and this would provide novel insight into the handling of Trp-containing peptides/proteins. Consequently, we have been trying to evaluate the photochemical properties of Trp, as well as other essential amino acids, focusing on their photosensitivity, photodegradation, and their ability to induce lipid peroxidation. Among all the essential amino acids tested, Trp exhibited the maximal level of superoxide anion generation under 18 h of light exposure (30000 lux). UV spectral analysis of Trp suggested the absorbability of UVA/B light, and exposure of Trp, in both solid and solution states, to UVA/B light resulted in significant photodegradation (t0.5: 18 h) and gradual color changes. In addition, photoirradiated Trp generated lipoperoxidant, a causative agent of photoirritation, and this might be associated with ROS generation.

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“…A decomposição subseqüente destes intermediários via quebra da ligação entre os carbonos C 2 -C 3 origina N-formilquinurenina, 3α-hidroperoxipirroloindol e 3α-hidroxipirroloindol. A decomposição do 3α-hidroperoxipirroloindol e do 3α-hidroxipirroloindol também gera N-formilquinurenina [38][39][40] (Esquema 1). Os produtos finais da oxidação -Nformilquinurenina e quinurenina -têm sido detectados tanto em resíduos livres do aminoácido quanto em resíduos de triptofano de peptídios e proteínas 35 .…”

Section: Reação Com Resíduos De Triptofanounclassified

Oxidação de proteínas por oxigênio singlete: mecanismos de dano, estratégias para detecção e implicações biológicas

Ronsein¹,

Miyamoto²,

Bechara³

et al. 2006

Quím. Nova

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Photosensitized oxygenation of Nb-methyltryptamine

Cited by 51 publications

References 11 publications

A valid model for the mechanism of oxidation of tryptophan to formylkynurenine—25 years later

A valid model for the mechanism of oxidation of tryptophan to formylkynurenine—25 years later

Photoreactivity of Amino Acids: Tryptophan-induced Photochemical Events via Reactive Oxygen Species Generation

Oxidação de proteínas por oxigênio singlete: mecanismos de dano, estratégias para detecção e implicações biológicas

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