A substance prepared by the oxidation of adrenaline with iodic acid and described in the literature as 2-idoosoadrenochrome appears, after consideration of a number of its physical and chemical properties to be identical with 2-iodoadrenochrome. ?'he iodine atom in iodoepinochrome, obtained by the oxidation of epinine with potassium iodate, has been shown to be in the 2-position of the heterocyclic ring in the molecule.During the course of a study of the infrared spectra of the aminochro~nes and related compounds (1) it was observed that the spectruin of a substance described by Macciotta as 2-iodooxoadrenochro~ne (iormulated as I) (2) was identical with those obtained from specimens of 2-iodoadrenochrome (usually formulated as 11) prepared by the methods described in the literature (3, 4, 5 , 6). The general form of the spectruln was more in keeping with a structure of type I1 than with one of type I. A definite hydrogen-bonded 0-H stretching band was observed a t 3410 cm-I (microanalysis indicated that the compounds were anhydrous and therefore this peak could not have arisen from water of crystallizatioil in I, and the "carbonyl" region was very similar to that oi adrenochrome, usually formulated as I11 (cf. 7). I t occurred t o the authors that the possibility that Macciotta's compound was, in fact, merely 2-iodoadrenochrome (11) should be investigated, especially since 110 other "oxoa~ninochromes" have been isolated. The preparation, in solution, of "oxoadrenochrome" was reported (8), but this claim has since been disputed (9). These compounds, which are very dark violet-brown in color, deco~npose on heating without melting and co~lsequently ~nelting point and nixed melting point deter~ninations gave only inco~lclusive results. T h e a~lalytical values obtained for carbon, hydrogen, and nitrogen were in good agreement in both cases with those calculated for 11, although i t nus st be admitted that only the hydrogen values are sufficiently different in the two cases to warrant drawing ally conclusions. T h e ultraviolet and visible absorption spectra of I and I1 were identical and very similar to those of 2-iodoa1~1i11ocl1ro111es in general (cf. 3). If I had the structure assigned to it by ;\/Iacciotta it would contain a different chrornophoric system t o the 2-iodoaminochromes and would be expected to exhibit a different absorption spectrum.i\/Iacciotta reported that reduction of I with sodium hydrosulphite gave 3,5,6-liMa
N-Ethylnoradrenochron~e, N-isopropylnoradrenochro~ne, adrenochrome methyl ether, adrenochrome ethyl ether, and their 2-iodo derivatives have been prepared in crystalline form. The action of acetic anhydride in pyridine on these aminochromes has been studied; acetylated rearrangement products were obtained in each case. N-Ethylnoradrenochrome monosemicarbazone, N-ethylnoradrenolutin, 5,6-diacetoxy-N-ethyl-2-iodoindole, and 5,6-diacetoxy-2-iodo-N-isopropylindole have been prepared. The ultraviolet and visible absorption spectra of the aminochromes described above and several 5,6-diacetoxy-and 3,5,6-triacetoxy-N-allrylindoles have been measured and the paper chromatographic behavior of the unhalogenated arninochromes studied.
The paper chro~natographic behavior of several 5,6-dihydrosyindoles has been studied. The colors given by nine dihydroxyindoles with 16 chrornogenic reagents are reported. The R, values of this group of compounds on Whatman No. 1 paper with 2% acetic acid in water or n-butanollacetic acid/water (6:1:2) as running solvents have been determined. The 5,6-dihydroxyindoles can be chromatographed satisfactorily using ZaHaroni-type systems (i.e. formamide-treated paper and non-polar running solvents). Satisfactory R, values can also be obtained for the 5,6-diacetoxyindoles on formamide-treated paper using a suitable non-polar mobile phase. The preparations of several new 5,6-dihydroxyindoles and 5,6-diacetoxyindoles are described and improved procedures for the syntheses of some known members of these groups are reported.The importance of the 5,6-dihydroxindoles as intermediates in the production of the dark pigillents known as melanins, in plants and animals, has been recognized for some time (for references see reviews by Lerner (I), Mason (2), and Thoinas (3)), but it is only in relatively recent years that many of these highly reactive compounds have been obtained in pure crystalline form (see (3) and (4) for references). Although there has been a considerable voluine of work carried out on the chromatography of the indoles in the past decade, there have been relatively few studies reported of the paper chromatographic behavior of the 5,6-dihydroxyindoles and their derivatives. In a study of the urine melanogens observed in cases of malignant melanoma of the liver, Leonhardi reported the R J values of some 5,6-dihydroxyindole derivatives (e.g. 0-acetyl, 0-methyl, 0-sulphatoxy, etc.) in several different solvent systems. These compounds were employed as models for the urinary melanogens which were considered by Leonhardi to be 5,G-dihydroxyindole derivatives (5). During an investigation into the metabolism of P-(3,4-dihydroxyphei1yl)-alanine in albino rats Pellerin and D'Iorio obtained a product with a RJ of 0.85 in a n-butanol/acetic acid/water system which they suggested was possibly 5,G-dihydroxyindole (6).One of the main difficulties encountered in carrying out paper chromatographic studies with the 5,G-dihydroxyindoles is the ease with which they undergo destructive oxidation to inelanitic pigments, especially under alkaline conditions; consequently basic solve~lt systems, including the isopropanol/aqueous ammonia systeills widely favored for indole chromatography, are quite useless with this group of indole derivatives. In an investigation of the reduction of adrenochrome with various reducing agents, carried out in these laboratories (7,8,9), we have made extensive use of paper chromatographic procedures in the examination of the reaction products. R4any of the products encountered in this program were either 5,G-dihydroxyindoles or their derivatives, and one of the most satisfactory systems for the study of these reaction mixtures was found to be 2% acetic acid in water using chromatographic paper ...
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