Glycogen-storage-disease-relating linear tetra-, hexa-, and octasaccharides of D-glucose having α(1→4) and α(1→6) linkages were synthesized using a stereoselective dehydrative glycosylation with a reagent mixture of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, N,N-dimethylacetamide, and triethylamine. A cross-condensation of a quasi-stoichiometric amount of a donor and an acceptor of an octasaccharide, followed by deprotection, afforded a glucohexadecasaccharide.
Abstract The photolysis and the thermolysis of the title compounds (I) were studied. The photolysis of (I) at low temperature gave 3-alkenyl-1-azirine (II) but at room temperature gave (II), pyrrole (III) or butenonitrile (IV) depending on the nature of the substituents of (I). The thermolysis of (I) gave (III), (IV) or 2H-pyrrole (V).
Chymotrypsin was modified in the zymogen form with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine (activated PEG2), followed by activation with trypsin. The modified enzyme was soluble in benzene and retained its enzymic activity. Acid-amide bond formation by the modified enzyme proceeded efficiently in benzene: N-benzoyltyrosine butylamide was made from N-benzoyl-L-tyrosine ethyl ester and n-butylamine, and benzoyltyrosine(oligo)phenylalanine ethyl esters were formed from N-benzoyl-L-tyrosine ethyl ester and L-phenylalanine ethyl ester.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemical reactions by polyethylene glycol-modified enzymes in chlorinated hydrocarbonsKatsunobu Takahashi, Ayako Ajima, Takayuki Yoshimoto, Masato Okada, Ayako Matsushima, Yutaka Tamaura, and Yuji InadaCite this: J. Org. Chem. 1985, 50, 18, 3414–3415Publication Date (Print):September 1, 1985Publication History Published online1 May 2002Published inissue 1 September 1985https://pubs.acs.org/doi/10.1021/jo00218a036https://doi.org/10.1021/jo00218a036research-articleACS PublicationsRequest reuse permissionsArticle Views220Altmetric-Citations75LEARN 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
The structures of cycloalkanone-based threo and erythro aldols were investigated by systematic introduction of stereo-determining factors. The combination of single-crystal X-ray analysis and cryoscopic measurement and solution NMR and IR studies elucidated the detailed geometry of these typical aldols. Currently, X-ray diffraction is the only reliable spectroscopic method to determine the relative configuration of aldols. Empirical NMR analysis can be safely applied in only limited cases. In hydrocarbon solvents, many aldols exist as monomers with an intramolecular OH...O=C hydrogen bond, but some compounds are in an equilibrium with higher aggregates via intermolecular hydrogen bonds. The aldols take various staggered conformers, where the relative stabilities are controlled largely by torsional strain affected by the size and nature of substituents. The intramolecular and intermolecular hydrogen bonds, gauche interactions between the vicinal substituents, and sometimes CH/pi attractions significantly influence the distribution of conformers. The preferred structure in solution often differs greatly from the crystalline-state geometry.
The kinetics of the direct catalytic conversion of acetone and hydrogen into methyl isobutyl ketone (MIBK) were investigated in the liquid phase using palladium–zirconium phosphate as a catalyst. Kinetic studies on the conversion of acetone into mesityl oxide (4-methyl-3-pentene-2-one) and its hydrogenation were separately carried out using the same catalyst. It was found that the direct reaction proceeded via a sequence of processes: mesityl oxide was first formed by condensation of acetone on acid sites of the catalyst and MIBK was then produced by hydrogenation of the mesityl oxide on palladium metal in the catalyst. Moreover, the experimental results were well interpreted by assuming that the condensation of acetone was controlled by a surface reaction between the acetone molecules adsorbed on the catalyst surface and that the rate of hydrogenation of mesityl oxide was determined by a surface reaction between dissociated hydrogen atoms and adsorbed mesityl oxide molecules.
