Stereochemie von Betanidin und Isobetanidin. 8. Mitteilung. Zur Konstitution des Randenfarbstoffes Betanin

Wilcox, M. E.; Wyler, Hugo; Dreiding, Aǹdré S.

doi:10.1002/hlca.19650480519

Cited by 40 publications

(18 citation statements)

References 14 publications

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“…The origin of the many isobetacyanins isolated from plants [lb] [3a] needs, therefore, to be reexamined. It is known that epimerization of betacyanins to isobetacyanins and vice versa takes place easily under alcaline conditions [I 11 [20]. A possible epimerization in the plant may not be necessarily due to enzymatic action; some general-base catalysis in the aged cell or the conditions of isolation could be responible for the artificial formation of is0 betacyanins.…”

Section: R'mentioning

confidence: 99%

2,3‐ and 4,5‐Secodopa, the Biosynthetic Intermediates Generated from L‐Dopa by an Enzyme System Extracted from the Fly Agaric, Amanita muscaria L., and Their Spontaneous Conversion to Muscaflavin and Betalamic Acid, Respectively, and Betalains

Terradas

Wyler

1991

Helvetica Chimica Acta

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An enzyme is extracted from the red peel of Amanita muscaria which cleaves the C(2)-C(3) and the C(4)-C(5) bond of the aromatic ring of L-dopa (1) to form a mixture of 4,5-secodopa ( = salt of 6-amino-2-hydroxy-4-(2'-oxoethylidene)hept-2-enedioic acid; 2) and 2,3-secodopa ( = salt of 7-amino-5-formyl-2-hydroxyocta-2,4-dienedioic acid; 3), two hitherto hypothetical biosynthetic intermediates (see Scheme). Though isolation of these products has not been possible, structural evidence is inferred from reaction products, kinetics, and spectroscopical characteristics in comparison with known compounds. Secodopas 2 and 3 are characterized in dilute solution by HPLC and UVjVIS spectroscopy (anions: I,,, 424 and 414 nm, resp., E~~~ = 25 500; on acidification, shift to 380 and 372 nm, resp.). They cyclize without enzyme catalysis, optimally at pH 4.5-5; 3 produces muscaflavin (5) and 2 betalamic acid (4). The products are identified by direct comparison with authentic samples in HPLC, by 'H-NMR of 5, and by condensation of 4 with L-proline to form the well known betalain indicaxanthin (7). The enzymatic conversion of L-dopa (1) via 2 to betalamic acid (4; (5')) and its condensation with L-proline leads to pure natural indicaxanthin (7; (2S, 1 1s)); correspondingly, the enzymatic conversion of o-dopa to (R)-betalamic acid and its condensation with L-proline produces isoindicaxanthin ((2S,IlR)) which is unknown in nature. Particularly relevant is the fact that the same enzyme cleaves pyrocatechol to produce a solution of the enolate form of the known 2-hydroxy-6-oxohexa-2,4-dienoate (secopyrocatechol; 9; see Fig. 5 ) . Dissociation constants of the corresponding enolic functions in the cleavage products are determined by spectrometric titration and compared to those of known systems.

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Section: R'mentioning

confidence: 99%

2,3‐ and 4,5‐Secodopa, the Biosynthetic Intermediates Generated from L‐Dopa by an Enzyme System Extracted from the Fly Agaric, Amanita muscaria L., and Their Spontaneous Conversion to Muscaflavin and Betalamic Acid, Respectively, and Betalains

Terradas

Wyler

1991

Helvetica Chimica Acta

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“…The cationic tetrahydroquinolinium ring of the anachelin chromophore reminded us of the corresponding dihydroindolinium systems found in, for example, the pigments betanidin [17,18] and the melanins. [19] The biosynthesis of melanins (melanogenesis) has been under investigation for the last 80 years [20,21] and is still under intense mechanistic scrutiny.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Studies on the Tyrosinase‐Catalyzed Formation of the Anachelin Chromophore

Gademann

2005

ChemBioChem

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The complex secondary metabolite anachelin, isolated from the freshwater cyanobacterium Anabaena cylindrica, is believed to act as siderophore, facilitating iron uptake. Its structure is characterized by a fascinating blend of polyketide, peptide, and alkaloid fragments. In particular, the tetrahydroquinolinium-derived chromophore is unique among natural products, and its biosynthesis is unknown. We propose a hypothesis for the biogenesis of the anachelin chromophore starting from a C-terminally bound L-Tyr residue. It is proposed that this amino acid is reductively aminated, methylated, and hydroxylated. Oxidation of this catechol diamine substrate by a tyrosinase would lead to an o-quinone, which would react by intramolecular aza-annulation and tautomerization to give the anachelin chromophore. In order to evaluate this hypothesis, a model substrate related to the proposed biogenetic precursor was prepared. It was shown that the enzyme tyrosinase is able to transform this substrate into an anachelin chromophore derivative, which corroborates the biogenetic hypothesis. In order to gain further insight into the mechanism of this transformation, we performed spectrophotometric reaction monitoring, allowing the formation of the expected product to be observed. In addition, a rise in absorption at around 250 nm might be due to the presence of a spiro five-membered ring intermediate resulting from an alternative 1,4-addition to the o-quinone. Lastly, we were able to show that the action of tyrosinase on this substrate follows Michaelis-Menten kinetics (k(cat)=123 s(-1) and K(m)=8.66 mM). Interestingly, the catalytic efficiency is decreased only by a factor of 30 relative to the natural substrate L-DOPA.

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“…= Integration normiert auf ein Proton. 4 wurde erkllrt, dass die 'H-NMR-Spektren mit der Annahme eines planaren Isomerieelementes an der C(12),C( 13)-Bindung vertraglich ist. In diesem Kup.…”

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“…Dies korreliert rnit der fruheren Beobachtung [4], dass die Epimerisierung von Betanidin (1/2) in Isobetanidin (12/13) an C(15), und nicht an C(2), stattfindet und dass sie in CF,COOH-Losung sehr langsam ablauft. Das 'H-NMR-Spektrum von reinem [4] Isobetanidin (12/13) in CF,COOH-Losung (Kolonnen 6 und 7 der Tabelle) zeigt, dass es praktisch die gleichen Signale aufweist wie Betanidin (1/2). Neben den acht schon fruher [4] (8,90(d), 6,90(s) und 6,04(s) ppm) auf, die je 0,35 Protoneinheiten entsprechen2)*).…”

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Deuterierung von Betanidin und Indicaxanthin, (E/Z)‐Stereoisomerie in Betalainen

Wyler

Dreiding

1984

Helvetica Chimica Acta

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SummaryPreviously unexplained 'H-NMR signals of the red-violet betanidine and of the yellow indicaxanthine in CF,COOH are interpreted with the help of deuteration experiments in CF,COOD. They confirm the 1,7-diazaheptarnethinium chromophore of these pigments and further show an (E/Z)-stereoisomerism at one of the partial double bonds: both betanidine and isobetanidine, in CF,COOH solution, consist of a -75:25 mixture of the ( 1 2 4 -(1 resp. 12) and the (122)

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Stereochemie von Betanidin und Isobetanidin. 8. Mitteilung. Zur Konstitution des Randenfarbstoffes Betanin

Cited by 40 publications

References 14 publications

2,3‐ and 4,5‐Secodopa, the Biosynthetic Intermediates Generated from L‐Dopa by an Enzyme System Extracted from the Fly Agaric, Amanita muscaria L., and Their Spontaneous Conversion to Muscaflavin and Betalamic Acid, Respectively, and Betalains

2,3‐ and 4,5‐Secodopa, the Biosynthetic Intermediates Generated from L‐Dopa by an Enzyme System Extracted from the Fly Agaric, Amanita muscaria L., and Their Spontaneous Conversion to Muscaflavin and Betalamic Acid, Respectively, and Betalains

Mechanistic Studies on the Tyrosinase‐Catalyzed Formation of the Anachelin Chromophore

Deuterierung von Betanidin und Indicaxanthin, (E/Z)‐Stereoisomerie in Betalainen

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