Acid-catalyzed Transformations Research Articles

On the formation of quinoline alkaloids in plants. 4. Concerning the mechanism of cyclopenase activity

Cyclopenase, an enzyme from the mycelium of Penicillium viridicatum Westling and Penicillium cyclopium Westling catalyses the transformation of the benzodiazepine derivatives (–)‐cyclopenine and (–)‐cyclopenol to the quinoline derivatives viridicatine and viridicatol, respectively. This rearrangement, which is connected with the elimination of molar amounts of CO2 and methylamine takes place in an nonenzymatic process too, if (–)‐cyclopenine and (–)‐cyclopenol are treated with acids or Lewis acids. In anhydrous medium instead of CO2 and methylamine, methylisocyanate is obtained. 14CO2 is formed from (–)‐[5‐14C]cyclopenine either by the enzyme or by the acid‐catalysed transformation, the viridicatine being inactive (Table). In experiments with 2H2O or H218O as solvents neither the cyclopenase nor the acid‐catalysed rearrangement proceeded with a significant incorporation of 2H or 18O (Fig. 1).These experimental results indicate that:a) enzymatic and nonenzymatic transformations of the investigated benzodiazepines to the corresponding quinoline derivatives proceed by similar mechanisms,b) closure of the hetero‐ring of the quinoline moiety involves C‐atoms 5a and 10 of the benzodiazepine compounds andc) the hydroxyl group in position 3 of the quinoline ring is derived directly from the epoxide oxygen.In Scheme 1 a possible reaction sequence for the transformation is given.

Skeletal rearrangement of α-hydroxy-ketones upon electron impact

A skeletal rearrangement induced by electron impact in a number of α-hydroxy-ketones has been studied. Methyl, ethyl, and possibly hydrogen undergo ready 1,2-shifts. The rearrangement is not brought about by thermal excitation and is analogous to the acid-catalysed acyloin transformation described by Favorskii. Evidence is presented that the electron-impact induced transformation proceeds by rearrangement of the molecular ions, and the possibility of determining migratory aptitudes is discussed.

Chemistry of erythronolide B. Acid-catalyzed transformations of the aglycone of erythromycin B.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemistry of erythronolide B. Acid-catalyzed transformations of the aglycon of erythromycin BThomas J. PerunCite this: J. Org. Chem. 1967, 32, 7, 2324–2330Publication Date (Print):July 1, 1967Publication History Published online1 May 2002Published inissue 1 July 1967https://doi.org/10.1021/jo01282a051RIGHTS & PERMISSIONSArticle Views155Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (897 KB) Get e-Alerts Get e-Alerts

The Kinetics of the Acid-catalyzed Transformation of Peroxybenzoic Acids to Acetyl Benzoyl Peroxides in Acetic Acid

Abstract It has been confirmed by paper chromatography that peroxybenzoic acid in acetic acid is transformed reversibly to acetyl benzoyl peroxide in the presence of a catalytic amount of sulfuric acid. The rate satisfies the first order equation for reversible reactions. The plot of the logarithm of the forward rate constant vs. the acidity function has given a straight line with a slope of −0.96. The rate decreases upon the introduction of an electronattracting group to the benzene ring of peroxybenzoic acid, the Hammett’s ρ-value being −0.37. A mechanism analogous to that postulated previously with peroxyacetic acid, which involves a rate-determining attack of protonated acetic acid on peroxybenzoic acids, is consistent with these facts.

Kinetics of the Acid-catalyzed Transformation of Peroxyacetic Acid to Acetyl Peroxide in Acetic Acid

<b>Kinetics of the Acid-catalyzed Transformation of Peroxyacetic Acid to Acetyl Peroxide in Acetic Acid</b>