Labelling indole

Synthesis of radioactively labelled indole-3-acetaldehyde, indole-3-ace-taldoxime and indole-3-acetonitrile... 

The previous discussion is a clear example of the separation of dynamic and structural influences on NMR spectra. Before a detailed analysis of anisotropic spin interaction data can be realized, the dynamic averaging of the tensors must be appreciated. In fact, a detailed description of local dynamics can be achieved in which models of the motions are characterized by an axis fixed in the molecular frame, an amplitude for the motion and a motional model, such as diffusion within an arc or three site jumps, etc. [21]. The data in Fig. 6.4.6 shows that the averaging of the tensor above 200 K for this labeled indole site is anisotropic [22]. 

Lack of a direct effect of morphine on the synthesis of pineal carbon-14 labeled indoles in organ culture... 

The first report of enzyme catalyzed esterification of lAA was made by Kopcewicz et al. [117], who studied the synthesis of lAA esters by incubating radiolabeled lAA with a com endosperm enzyme preparation. Following incubation, ammonia was added to the incubation mixture and the amount of labeled indole-3-acetamide formed was used as a measure of the amount of lAA ester synthesized. Ester synthesis was found to be stimulated by ATP and CoASH, suggesting acyl group activation. Later studies by Michalczuk and Bandurski [118,119] used a more direct assay procedure, and indicated the following two step reaction mechanism involving sugar, not lAA, activation ... 

In 1992, Xia and Zenk could show in feeding studies with C-labelled indole and 3- C-labelled (S)-tryptophan on various plants, including Polygonum tinctorium, Indigofera tinctoria and Isatis tinctoria, that the metabolism does not involve tryptophan directly, but proceeded via indole. [16] In the biosynthesis of indoxyl, tryptophan is first degraded, by means of a tryptophanase, to indole, and this is then hydroxylated. [17] Finally, indoxyl binds to various sugars. 

D. Hendry, N.S. Nixon, B.S. Roughley, et al (2004) The synthesis of carbon-14 labelled indoles, in Synthesis and Applications of Isotopically Labelled Compounds, vol. 8 (eds D.C. Dean, C.N. Filer, and KE. McCarthy), John Wiley Sons, Ltd, New York, pp. 25-28. 

Eliezer J, Morris DA (1979) Effects of temperature and sink activity on the transport of " C-labelled indol-3yl-acetic acid in the intact pea plant Pisum sativum L.) Planta 147 216-224... 

Coombe BG (1976) The development of fleshy fruits. Annu Rev Plant Physiol 27 207-228 Eeuwens CJ, Schwabe WW (1975) Seed and pod wall development in Pisum sativum L. in relation to extracted and applied hormones. J Exp Bot 26 1-14 Elisezer J, Morris DA (1979) Effects of temperature and sink activity on the transport of " C-labelled indol-3yl-acetic acid in the intact pea plant Pisum sativum L.). Planta 147 216-224... 

Applications of tryptophan synthetase Tryptophan synthetase (EC 4.2.1.20) is a pyridoxal phosphate-dependent enzyme that, in the cell, catalyzes the a,/3-elimination of water from serine to form a pyridoxyl-bound a-aminoacrylate, which undergoes Michael addition of indole to form the named amino acid. This type of reaction has been used to prepare (5)-tryptophan isotopomers with a variety of labeling patterns by use of different labeled indoles and (5)-serines in yields of up to 98% based on indole and 92% based on (5)-serine. 

The reductive activation reaction of the 13C-labeled pyrrolo[ 1,2-a]indole shown in Scheme 7.14 was carried out in methanol and a 13C-NMR spectrum was obtained for the crude organic extract. This 13C-NMR spectrum, shown in Fig. 7.14, reveals the presence of starting material as well as products with 13C-labeled alkene and alkane centers. We confirmed the 13C assignments shown... 

In a recent study, we showed that the more flexible pyrido[l,2-a]indole-based cyclopropyl quinone methide is not subject to the stereoelectronic effect.47 Scheme 7.17 shows an electrostatic potential map of the protonated cyclopropyl quinone methide with arrows indicating the two possible nucleophilic attack sites on the electron-deficient (blue-colored) cyclopropyl ring. The 13C label allows both nucleophile attack products, the pyrido[l,2-a]indole and azepino [l,2-a]indole, to be distinguished without isolation. The site of nucleophilic is under steric control with pyrido [1,2-a]indole ring formation favored by large nucleophiles. 

FIGURE 7.16 Trapping of the phosphate of 5 -dGMP by the pyrido [1,2-a] indole quinone methide. The 13C-NMR shows most trapping with ring retention, labeled pyrido, with trace amounts of ring expansion, labeled azepino. ... 

TABLE 7.2 Autoradiogram of the Reductive Cleavage of a 5 -32P End-Labeled 514 bp Restriction Fragment from pBR322 DNA (Ecorl/Rsal) by Cy cl open t />] indoles... 

Cyanine dyes also are used as labels for oligonucleotide probes. Unlike the hydrophilic cyanine dyes valuable for protein labeling, the use of dye-phosphoramidite compounds to synthesize DNA or RNA probes typically requires the use of more hydrophobic dye structures to make them compatible with the solvents and reactions of oligonucleotide synthesis. Thus, indol cyanines containing few or no sulfonates are used in these applications to label oligos for applications such as array detection, hybridization assays, and RT-PCR. 

We chose the microwave-enhanced Raney Nickel catalyzed hydrogen isotope exchange of indole and N-methylindole as our substrates and D20, CD3COCD3, CD3OD and CDC13 as the solvents. The thermal reaction had already been the subject of a recent study [44], The microwave-enhanced method was some 500-fold faster than the corresponding thermal reaction (at 40 °C). Furthermore the pattern of labeling (Scheme 13.3) varied with the choice of solvent. Thus in the case of indole it-... 

Depending on the nature of the substituents X1, X2, and X3, the reactions produced nitrones (148) (as indole derivatives) or annelated isoxazolines (149). The authors performed a series of experiments (including one with the use of a deuterium label) and suggested a mechanistic scheme for the interpretation... 

Results and data gathered on mass spectroscopy of various indole alkaloids have been summarized by Hesse (320). The derivation of the characteristic fragments of indolo[2,3-a]quinolizidines has been interpreted by Gribble and Nelson (321), who investigated C-3, C-5, C-6, C-20, and C-21 deuterated derivatives of octahydroindolo[2,3-a]quinolizine (1). Kametani et al. have observed and proved, with labeled compounds, a methyl transfer from the ester function of reserpine derivatives to the basic nitrogen atom during mass-spectroscopic measurement (322). 

The incorporation of acetate into the monoterpene unit of the indole alkaloids has recently been reexamined (176). Using [l,2- C2]acetate it was established that no intact incorporation occurred, and a similar labeling pattern to that from [2- C2]acetate was observed, i.e., C-3, C-4, C-20, C-22, and C-23. Extensive scrambling of the acetate occurred via the Krebs cycle to label the 1 and 2 positions of acetate prior to incorporation. [2- C]Mevalonate was incorporated equally into C-17 and C-22 of ajmalicine (39), indicating that an equilibration occurs at some point in the pathway, as had been established previously with radiolabeled precursors 176). 

In 1990, Nakamura et al. reported for the first time the complete biosynthetic origin of the whole carbon skeleton of carbazomycin B isolated from lower plants (378). Based on feeding experiments with and C-labeled compounds, followed by measurement of radioactivity and C-NMR spectroscopy, it was shown that L-tryptophan (408) contributes to C-3 and C-4 of the hexasubstituted aromatic ring, in addition to the indole ring, indicating tryptophan as the progenitor of carbazomycin B (261), in contrast to Chakraborty s proposal of 2-methylcarbazole. The indole part of L-tryptophan (408) is formed by incorporation of two carbons from phosphor-ibosyl diphosphate (430), with loss of the anthraniiic acid (397) carboxyl. The... 

In times past it was thought that indoles already bearing an alkyl substituent at C-3 were further alkylated by direct attack at C-2. However, although 2,3-dialkylindoles are readily formed the reaction still involves attack at C-3. This can be demonstrated by the example in Scheme 7.3, where 3-(4 -hydroxybutyl)indole, containing an isotopic label located at C-T, is treated with boron trifluoride in diethyl ether. Two 1,2,3,4-tetrahy-drocarbazoles (l,2,3,4-tetrahydrodibenzo[6,J)pyrroles) are formed in a ratio of 1 1. These differ only in the position of the label. This result indicates that a 3,3-spiroindoleninium intermediate is formed first, and this then undergoes rearrangement of either bond a or bond b to C-2. As the two bonds a and b are identical, equal amounts of the tetrahydrocarbazoles... 

Fig. 2.4. Chromatographic profiles of volatiles emitted by four plant species at different time periods after an attack by Spodoptem littoralis larvae. The labeled peaks are 1, (Z)-3-hexenal 2, ( )-2-hexenal 3, (Z)-3-hexenol 4, (Z)-3-hexenyl acetate 5, linalool 6, ( )-4,8-dimethyl-1,3,7-nonatriene 7, indole 8, ( )-/ -caryophyllene 9, ( ,)-o -bergamotene 10, ( >/3-farnesene 11, ( , )-of-farnesene 12, nerolidol 13, ( , )-4,8,12-trimethyl-1,3,7,11-tridecatetraene 14, of-pinene 15, /3-pinene 16, -myrcene 17, D-limonene 18, ( )-/3-ocimene 19, -sesquiphellandrene 20, germacrene D. Two internal standards, -octane and nonyl acetate, are labeled with IS1 and IS2, respectively.

The synthesis of a C-labelled version of naratriptan (3b) is highlighted in Scheme The indole ring of naratriptan hydrochloride (3) was oxidatively cleaved using sodium periodate to give ketoformanilide 45. Cyanation of 45 with potassium [ C]cyanide in aqueous ethanol gave the intermediate amidine 46, which was reduced directly with NaBH4 in acetic acid to afford C-labelled naratriptan (3b), which was isolated as the hydrochloride salt. 

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