Earthquakes and Continents

Hamilton, Bill

doi:10.1080/00357529.1969.11764036

Cited by 4 publications

(7 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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), 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).…”

mentioning

confidence: 84%

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.

104

View full text Add to dashboard Cite

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...

show abstract

mentioning

confidence: 84%

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.

104

View full text Add to dashboard Cite

show abstract

“…where /a(0) is the intensity of the inverted signal (i.e., « ), and /a(") is the intensity of the equilibrium signal (i.e., » )• Therefore, if A and B are overlapping multiplets, signal A is isolated at = tb, and B is isolated at = ta. From a knowledge of ta, tb, /a(tb), and /b(ta), we can compute the intensity of A in the inverted spectrum, /a(0), from /q\ __cxIaÍtb)_ (2) (1 + a) exp(-[tb/ta] In (1 + a)) -1 W and from eq 1, with analogous formulas for 7b(0) and , •…”

Section: Resultsmentioning

confidence: 99%

“…Hamilton first suggested that an electrophilic "oxenoid" species is generated in these reactions by transfer of two electrons to oxygen prior to, or concurrent with, transfer of an oxygen atom to the substrate. [1][2][3][4] This mechanism has found particular favor in accounting for the reaction of cytochrome-P-450-containing oxygenases, and especially the "NIH shift" which occurs during aromatic hydroxylation reaction.5•6 A number of organic model systems which undergo oxenoid-type reactions have also been designed and investigated. [1][2][3][4][5][6] Among the most well-suited of all "oxenoid" reactions in organic chemistry is the peracid epoxidation of olefins, and this reaction clearly proceeds through electrophilic attack on the olefin7-10 as evidenced, for example, by the well-documented effects of electron-donating or electron-withdrawing substituents.…”

mentioning

confidence: 99%

“…[1][2][3][4] This mechanism has found particular favor in accounting for the reaction of cytochrome-P-450-containing oxygenases, and especially the "NIH shift" which occurs during aromatic hydroxylation reaction.5•6 A number of organic model systems which undergo oxenoid-type reactions have also been designed and investigated. [1][2][3][4][5][6] Among the most well-suited of all "oxenoid" reactions in organic chemistry is the peracid epoxidation of olefins, and this reaction clearly proceeds through electrophilic attack on the olefin7-10 as evidenced, for example, by the well-documented effects of electron-donating or electron-withdrawing substituents. A diagnostic characteristic of peracid epoxidations is their absolute syn stereospecificity, even in cases where sub-stituents which could stabilize a carbonium ion intermediate are present.8-12 As Berti has pointed out,9 among the very large number of epoxidations of known steric course, there has not been reported a single instance of a cis olefin giving threo or a trans olefin giving erythro epoxide.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Enzymic epoxidation of trans,trans-1,8-dideuterio-1,7-octadiene. Analysis using partially relaxed proton Fourier transform NMR

May¹,

Gordon²,

Steltenkamp³

1977

J. Am. Chem. Soc.

View full text Add to dashboard Cite

“…Although the results from aromatization of deuteriumlabeled acid 14 do not exclude rigorously the possibility that salicylic acid formation occurs via carboxyl migration, the quantitative formation of o-and p-cresol from 19 and 20 indicates that carboxyl migration does not occur in cation 21 (or 15). It would appear that the intramolecular carboxyl migration in the biological hydroxylation of />-hydroxybenzoic acid to gentisic acid9 does not occur by 21 (R2 = H; R3 = OH), derived from oxirane ring opening of the arene oxide or by direct addition of HO+ (or HO• and subsequent oxidation) to 3.82 (s, 3 H) 6.85 (d, 6.35 (dd, 1 H, A4 = 5.9, 6.47 (dd, 1 H, A 5 5.78 (dd, 1 H, As A,5 = 10.6) = 10.6, A,6 = 5.9) = 5.9, A.7 = 5.2) A,7 = 5.2)…”

mentioning

confidence: 97%