The kinetics of the oxygen-exchange reaction at the anomeric carbon atoms of D-ribose and D-2-deoxyribose (2-deoxy-D-erythro-pentose) were compared using the O-18 isotope induced shift in C-13 NMR spectroscopy. Measurements were made at a number of temperature and pH values. The oxygen-exchange reaction for these sugars is strongly pH-dependent, displaying regions of acid, water, and base catalysis. At 25-degrees-C the oxygen-exchange rate of D-ribose was found to be approximately 20-fold greater than the rate for D-glucose between pH 2 and 9. In turn, the oxygen-exchange rate for D-2-deoxyribose was greater than the rate for D-ribose by approximately 5-fold above pH 4 and by greater than 10-fold below pH 4. The results are analyzed in terms of steric and inductive effects on the hydration kinetics of the open-chain forms and by comparison with the hydration reaction of simple aldehydes. The study also includes quantitative data, based upon C-13 NMR line intensities, for the various anomeric forms that exist in solutions of these sugars at the different temperature and pH values used in the kinetic measurements reported here. In each case, the oxygen-exchange reactions of the anomers are slow relative to the rate of anomerization, so that the anomers appear to exchange oxygen at the same rate.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe oxygen-18 isotope shift in carbon-13 nuclear magnetic resonance spectroscopy. 13. Oxygen exchange at the anomeric carbon of D-glucose, D-mannose, and D-fructoseTony L. Mega, Sergio Cortes, and Robert L. Van EttenCite this: J. Org. Chem. 1990, 55, 2, 522–528Publication Date (Print):January 1, 1990Publication History Published online1 May 2002Published inissue 1 January 1990https://pubs.acs.org/doi/10.1021/jo00289a026https://doi.org/10.1021/jo00289a026research-articleACS PublicationsRequest reuse permissionsArticle Views354Altmetric-Citations30LEARN 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 InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

AbstractDie aus (I) erhaltenen Imidazolone (II) sowie die Verbindungen (III)‐(V) werden auf anticonvulsive Wirkung untersucht.

Selectively substituted hydantoins 1 (15 examples), 4-hydroxy-2-imidazolidinones 2 (13 examples), 2-imidazolones 3 (10 examples), 2-imidazolidinones 4 (four examples), vicinal diamines 5 (two examples), and simple amino acid derivatives 6 (four examples) have been prepared and evaluated in the maximal electroshock seizure (MES), subcutaneous pentylenetetrazole seizure threshold (sc Met), and rotorod (Tox) tests. The medium effective doses (ED50) and the medium toxic dose (TD50) for the most active compounds are reported. In general, the most pronounced activity was observed for hydantoins 1 and protected amino acids 6. Within each series of compounds, enhanced anticonvulsant activity was often noted for compounds containing an aromatic group one carbon removed from a nitrogen atom. Among the most active compounds observed were the amino acid derivative N-acetyl-D,L-alanine benzylamide (6d) and the two 2-imidazolones 4-methyl-1-(phenylmethyl)-1,3-dihydro-2H-imidazol-2-one (3e) and 1-phenyl-1,3-dihydro-2H-imidazol-2-one (3g). Compound 6d proved to be slightly more potent in the MES test than phenacemide.

AbstractAus Hydantoinen (I) entstehen mit Lithiumalanat zunächst die entsprechenden Hydroxylverbindungen (II) in Form von cis‐ und trans‐Isome‐ ren.