2-Deuterioindole was prepared from N-phenylsulphonylindole by lithiation, quenching with D, O, and hydrolysis. Treatment of the 2-deuterioindole Grignard reagent with succinic anhydride gave 4-(indol-3-yl) -4-oxobutanoic acid with partial loss of the deuterium from the 2-position. 2,3-Dideuterioindole (prepared by acid-catalysed deuteriation of 2-deuterioindole) when treated in the same way, gave the indolyl oxobutanoic acid, 92% deuteriated at the indolyl 2-position. Reduction to the deuterioindolylbutanol and treatment of its toluene-p-sulphonate with potassium t-butoxide give 2-deuterio-spiro[cyclopentane-3'-(3H)indolel which was 88% deuteriated at the 2-position. The kinetics of the acid-catalysed rearrangement of the deuterioindolenine and its non-deuteriated analogue were measured and the ratio k,/k, of the pseudo-first-order rate constants was found to be 1.08, showing that the isotope effect was very small.
Deuterium labelling experiments show that the boron trifluoride-catalysed cyclisation at 90 "C of 4-(5-methoxyindol-3-yl) butanol (1 e) to 6-methoxytetrahydrocarbazole (f 1 a) occurs by two simultaneous pathways. The main route (83.5%) involves initial cyclisation at the 3-position of (1e) to give an intermediate spirocyclic indolenine which then rearranges to the tetrahydrocarbazole. The minor pathway (1 6.5%) involves direct attack at the 2-position. A similar duality of mechanism of substitution applies to the 6-methoxy-, 4,6-dimethoxy-, and 5,6-dimethoxy-indole analogues for which the extent of substitution at the 2-position can be correlated with the calculated change in x-electron density at the 2-and 3-positions for a series of methoxy-substituted 3-methylindoles. These calculations do not, however, fit the experimental findings for the 5-methoxy-derivative which appears to be anomalous, showing an unexpectedly high percentage of direct substitution at the 2-position. A possible explanation of this result is advanced.* A referee has suggested that the similarity of the substitution results between the 5-methoxy-and 5,6-dimethoxy-compounds in the latter compound.the unusual behaviour of the 5-methoxy-compounds in possible to account for this anomaly by considering the may be due to twisting out of conjugation of the 6-methoxy-group terms Of an effect* However, it does appear
Das deuterierte Indolylbutanol (Ia) cyclisiert zum Tetrahydrocarbazol (Ausb. 21%) bzw. seinem Trifluoracetat (III), wobei 83.5% des entstehenden Produktes aus der intermediären Spiroverbindung (II) hervorgehen, und 16.5% direkt gebildet werden.
A series of N‐1 or C‐2 phenylalkyl substituted tryptophans and C‐1 phenylalkyl substituted 3,4‐dihydro‐β‐carbolines were prepared from the apropriate aniline, 1b or 1e, or tryptophan, 8 or 11, by ring closure methods. None of the compounds prepared were more potent than 5‐bromotryptophan (11) as inhibitors of sickle cell hemoglobin gelation.
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