Indole 5,6-dihydroxy

Indole, 3-(dialkylaminomethyl-) alkylation, 4, 275 Indole, 2,3-dibromo-synthesis, 4, 215 Indole, 2,6-dibromo-3-methyl-synthesis, 4, 215 Indole, 1,3-dichloro-synthesis, 4, 214 Indole, dihydrodehydrogenation, 4, 283, 311 in non-silver photography, 1, 383 Indole, 2,3-dihydro-synthesis, 4, 327, 352 Indole, 2,3-dihydroxy-tautomerism, 4, 37, 199 Indole, 4,6-dimethoxy-... 

A tautomeric equilibrium between quinone and quinone methide tautomers has been proposed to exist for the compounds which are obtained by oxidation of 5,6-dihydroxy indole (Scheme 18) (92TL3045). 

CN [R, 5 -( )]-( )-7-[3-(4-fluorophenyl)-l-(l-methylethyl)-17/-indol-2-yl]-3,5-dihydroxy-6-heptenoic acid monosodium salt... 

Although 7,14-dihydroxy-6H,13H-pyrazino[l,2- 4,5-,T]bisindole-6,13-dione can jn pr ncipie exist in two tautomeric forms of the dihydroxy compound 39 and the diketo form 40, only the dihydroxy is observed <2003OBC3396>. Presumably this is due to the enolizable 1,3-dicarbonyl moieties and the formation of the indole ring, therefore leading to aromaticity and a net overall stabilization. 

All aminochromes undergo a slow spontaneous rearrangement in aqueous solution, although the rate is considerably affected by the structure of the aminochrome in question. The rearrangement of all aminochromes is however markedly catalyzed by alkali (see ref. 3 for early references). The structure of the fluorescent alkaline rearrangement product of adrenochrome was not ascertained until 30 years after the characteristic fluorescence reaction had been first reported,138 and the substance [i.e. adrenolutin, 5,6-dihydroxy-V-methylindoxyl (31), often formulated as 3,5,6-trihydroxy-V-methyl-indole (32), cf. refs. 3, 108] was finally isolated in crystalline form in 1949.139,140 Subsequently, A-ethyl-5,6-dihydroxyindoxyl (33) and... 

Dihydroxyindoles also form complexes readily with sodium bisulfite,118,123, 156 and the presence of the 5,6-dihydroxy -A-methyl-indole-sodium bisulfite addition complex among the products obtained... 

The alkali metal borohydrides reduce aminochromes in solution very rapidly 70,109,120,147,148,1B1,1B5,157 the expected 5,6-dihydroxy-indole derivative was usually obtained in high yield.161,166 Reduction of the 7-iodoaminochromes was not usually accompanied by deio-dination to any appreciable extent.109,166 A number of relatively minor, unidentified, often fluorescent, water-soluble by-products were usually also detected in the reduction mixtures.109,148,155... 

The reduction of adrenochrome (1) with ascorbic acid (59) was first reported in 1948,158 although the nature of the reaction products (which may be of physiological importance, cf. ref. 159) was not determined until several years later. It was shown by Heacock and Laidlaw in 1958 that reduction mixtures of this type contained at least three indolic products,147 one of which was isolated and shown to be 5,6-dihydroxy- -methylindole (28).147 The major component of aqueous adrenochrome-ascorbic acid reaction mixtures has recently been shown to be a secondary product (60) (which was isolated as its di- and tetra-acetyl derivatives) produced by the interaction of the o-dihydroxy group of 28 with the a-dicarbonyl function of dehydro-... 

The n.m.r. spectra of several 5,6-dihydroxyindoles (and their diacetyl derivatives) obtained by reduction of different non-halo-genated aminochromes were compared with those obtained from the appropriate 5,6-dihydroxy-(or 5,6-diacetoxy)-iodoindoles produced by reduction of the corresponding iodoaminochromes. The n.m.r. data clearly demonstrated the presence of a- and /3-protons in the indole nuclei (except in the case of the products derived from 2-methylnoradrenochrome and the corresponding iodoaminochrome,... 

The first step, by analogy with quinones, requires the addition of two atoms of hydrogen to give 1,3-dihydroxy indoles (137). AH attempts to isolate or identify these compounds by chemical means have been... 

Benzophenone, o-benzoylamino-indole synthesis from, 4, 329 Benzophenone, 2,3 -dihydroxy-cyclization, 3, 835... 

The crude sodium threo-(+/-)-(E)-3,5-dihydroxy-7-[3 -(4"-fluorophenyl)-l -(l"-methylethyl )indol-2 -yl]hept-6-enoate is dissolved in water, and the solution is acidified to pH 2 with 2 N hydrochloric acid and extracted with diethyl ether. The diethyl ether extract is washed three times with saturated sodium chloride solution, dried over anhydrous magnesium sulfate and evaporated at reduced pressure to obtain the crude solid racemic erythro-(+/-)-(E)-3,5-dihydroxy-7-[3 -(4"-fluorophenyl)-l,-(l"-methylethyl )indol-2 -yl] hept-6-enoic acid (6.9 g). 

High-energy irradiation of aqueous solutions of 5,6-dihydroxyindole (136) in the presence of azide ions yields the oxidized product (137) in equilibrium with the quinone (138). Reaction of the quinone (138) with azide leads to the trapped product (139) and subsequently to 6,7-dihydroxy-l,2,3-triazolo[4,5-6]indole (140). It appears that the driving force for this reaction (138)->(140) is the electrocyclic ring closure as the quinone (138) is unreactive towards other nucleophiles (Scheme 11) <92TL3045>. 

The mode of biosynthesis of none of these alkaloids is known but, in the case of the iboga group, some guesses have been made (39, 63, 64), all of which start from the amino acids, tryptophan and dihydroxy-phenylalanine, and involve a fission of the latter s aromatic ring. A more sophisticated approach (65), starting from precursors of the aromatic amino acids, namely shikimic and prephenic acids, is apparently not in agreement with recent work on other indole alkaloids (66). The genesis of most indole alkaloids appears to stem from tryptophan and three... 

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