The Reaction of 2-Methylindole with Pyruvic Acid

The reaction of 2-methylindole with pyruvic acid was studied. Two products are found to be depending on experimental conditions, including the 2:2 condensation adduct and the 2:1 condensation adduct. The reaction mechanism evidently involves a 1:1 adduct of 2-hydroxy-2-(2-methylindol-3-yl)-propionic acid as an intermediate.     

The Reaction of Indole Magnesium Bromide with Ketones I. The Reaction of Indole Magnesium Bromide with Cyclohexanone

Indole magnesium bromide, produced by reacting indole with n-butyl magnesium bromide in ether, was reacted with cyclohexanone at ice or room temperature to yield 1-(indol-I-yl)-cyclohexanol (I), which is unstable and may be decomposed easily into indole and cyclohexanone in acidic condition. Indole magnesium bromide reacted with cyclohexanone in refluxing benzene or in anisole at 80°C, to form two products, 1-(indol-3-yl)-cyclohexanol (II) and 1-(indol-3-yl)-cyclohexene (III). (II) could be converted to (III) by heating (II) in phosphoric acid. Reaction of III with maleic anhydride gave a Diels-Alder adduct (IV). Reaction of indole magnesium bromide with cyclohexanone in anisole at 130°C yielded (III) and a trimolecular condensation product of cyclohexanone (V).     

Bond and mode selectivity in the reaction of atomic chlorine with vibrationally excited CH2D2

The title reaction is investigated by co-expanding a mixture of Cl2 and CH2D2 into a vacuum chamber and initiating the reaction by photolyzing Cl2 with linearly polarized 355 nm light. Excitation of the first C-H overtone of CH2D2 leads to a preference for hydrogen abstraction over deuterium abstraction by at least a factor of 20, whereas excitation of the first C-D overtone of CH2D2 reverses this preference by at least a factor of 10. Reactions with CH2D2 prepared in a local mode containing two quanta in one C-H oscillator /2000>- or in a local mode containing one quantum each in two C-H oscillators /1100> lead to products with significantly different rotational, vibrational, and angular distributions, although the vibrational energy for each mode is nearly identical. The Cl+CH2D2/2000>- reaction yields methyl radical products primarily in their ground state, whereas the Cl+CH2D2/1100> reaction yields methyl radical products that are C-H stretch excited. The HCl(v=1) rotational distribution from the Cl+CH2D2/2000>- reaction is significantly hotter than the HCl(v=1) rotational distribution from the Cl+CH2D2/1100> reaction, and the HCl(v=1) differential cross-section (DCS) of the Cl+CH2D2/2000>- reaction is more broadly side scattered than the HCl(v=1) DCS of the Cl+CH2D2/1100> reaction. The results can be explained by a simple spectator model and by noting that the /2000>- mode leads to a wider cone of acceptance for the reaction than the /1100> mode. These measurements represent the first example of mode selectivity observed in a differential cross section, and they demonstrate that vibrational excitation can be used to direct the reaction pathway of the Cl+CH2D2 reaction.     

A Convenient Method for the Preparation of Ellipticine

A convenient method for the synthesis of ellipticine is reported. This synthesis is achieved by modifying the processes of Woodward and Sainsburg. The overall yield of this five step synthesis is 12 percent.     

PHOTODYNAMIC GENERATION OF HYDROXYL RADICALS BY HEMATOPORPHYRIN DERIVATIVE AND LIGHT

In a reaction mixture containing hematoporphyrin derivative, deoxyribose, Fe³⁺-EDTA and either methionine or tryptophan, hydroxyl radicals were formed during illumination with visible light. When either hematoporphyrin derivative, Fe³⁺-EDTA or the amino acid was omitted from the reaction mixture, the generation of hydroxyl radicals ceased. These observations suggest an iron-catalyzed Haber-Weiss reaction, involving superoxide and hydrogen peroxide in the generation of hydroxyl radicals. It could be shown that with methionine H₂O₂ was indeed an essential intermediate in the reaction sequence. With tryptophan, however, H₂O₂, was not generated. Apparently a photooxidation product of tryptophan could replace H₂O₂ in the OH-generating reaction with Fe²⁺-EDTA. Although superoxide was generated in the reaction mixture, it was not an indispensable intermediate. Apparently a porphyrin radical, formed via photoexcitation of hematoporphyrin derivative, could replace superoxide in the Haber-Weiss reaction.     

Enumeration of RNA structures by matrix models

We enumerate the number of RNA contact structures according to their genus, i.e., the topological character of their pseudoknots. By using a recently proposed matrix model formulation for the RNA folding problem, we obtain exact results for the simple case of an RNA molecule with an infinitely flexible backbone, in which any arbitrary pair of bases is allowed. We analyze the distribution of the genus of pseudoknots as a function of the total number of nucleotides along the phosphate-sugar backbone.