Search results for "HYDROLYSIS"
showing 10 items of 632 documents
ChemInform Abstract: Comparative Lipase-Catalyzed Hydrolysis of Ethylene Glycol Derived Esters. The 2-Methoxyethyl Ester as a Protective Group in Pep…
2010
ChemInform Abstract: Chemoselective Removal of Protecting Groups from O-Glycosyl Amino Acid and Peptide (Methoxyethoxy)ethyl Esters Using Lipases and…
2010
The selective C-terminal deprotection of O-glycopeptide (methoxyethoxy)ethyl esters is achieved under mild conditions (pH 6.6, 37 degrees C) by enzymatic hydrolysis using papain or lipase M from Mucor javanicus to give building blocks useful for chain-extending glycopeptide synthesis. On the other hand, the selective removal of acetyl protecting groups from the saccharide portion of glycopeptides is accomplished by alternative enzymatic hydrolysis with lipase WG from wheat germ to furnish model substrates for enzymatic glycosyl transfer reactions in order to extend the carbohydrate side chain of these conjugates.
A novel synthesis of 2-aryl-4-piperidones by mannich cyclization of iminoketals
1983
2-Aryl-4-piperidones have been synthesized by condensation between an aromatic aldehyde and a β-aminoketone ethylene ketal, and further cyclization of the resulting iminoketal with dry hydrogen chloride or anhydrous p-toluensulfonic acid. Alternatively, reaction of the above iminoketals with methyl fluorosulfonate followed by dry hydrogen chloride treatment and acid hydrolysis gives directly N-methyl-4-piperidones. The application of these reactions to the synthesis of some 2-aryl-3-acetylpyrrolidine systems is also described.
ChemInform Abstract: O-Boronato- and o-Trifluoroborato-Phosphonium Salts Supported by L-α-Amino Acid Side Chain.
2015
The synthesis of o-boronato- and o-trifluoroborato–phosphonium salts supported by the l-amino acid side chain is described. The synthesis of these new class of amino acid derivatives was achieved by stereoselective quaternization of o-(pinacolato)boronatophenylphosphine with β- or γ-iodo amino acid derivatives which are prepared from l-serine or l-aspartic acid, respectively. The quaternization of the phosphine was performed using either iodo amino ester or carboxylic acid derivatives. In addition, free carboxylic acid and amine derivatives were obtained by saponification or HCl acidolysis of o-boronato–phosphonium amino esters, respectively. The usefulness of these compounds in peptide cou…
Nachweis und chemische umsetzungen von endgruppen in polystyrolen
1955
Bei der Losungspolymerisation van Styrol mit dem Eisen-Redox-System Brombenzoylperoxyd/Fe/Benzoin werden Brombenzoesaure-Ester-Gruppen in das Makromolekul eingebaut; diese lassen sich quantitativ verseifcn. Dabei entstehen Polymere mit alkoholischen Endgruppen; diese konnen mit Dichlorphenylisocyanat umgesetzt und quantitativ bestimmt werden. Mit Brombenzopersaure/Fe/Benzoin erhaltene Polystyrole enthalten keine Brombenzoesaure-Esterendgruppen sondern alkoholische Endgruppen, die ebenfalls mit Dichlorphenylisocyanat umgesetzt wurden. Die alkoholischen und esterartjgen Endgruppen lassen sich ultrarotspektroskopisch nachweisen. In the solutionpolymerisation of styrene with the iron-redox-syst…
Speciation of trialkyltin(IV) cations in natural fluids
2004
The hydrolysis of (CH(3))(3)Sn(+), (C(2)H(5))(3)Sn(+) and (C(3)H(7))(3)Sn(+) has been studied in a Synthetic Seawater (SSW) ionic medium simulating the major composition of natural seawater, at different salinities (5 less than or equal to S less than or equal to 45), and at t = 25 degreesC. Interactions with anionic components of SSW, considered as single sea salt, are determined by means of a complex formation model. By potentiometric measurements (ISE-H(+) and ISE-F(-) electrodes), the model has been extended to also consider interactions of organotins with carbonate and fluoride ions, which are other important components of seawater. Literature and new values of hydrolysis constants in …
Thymine content of sea water as a measure of biosynthetic potential
1977
A hydrolysis procedure along with a high-pressure liquid chromatographic procedure is given enabling simple and reliable thymine determinations in the nanogram range in different fractions of sea-water samples taken from three different locations in the Northern Adriatic Sea. The levels corresponded to 1–3 μg DNA per liter. From total polyanionic thymine, which had been precipitated as the cetyltrimethylammonium salt, the highest percentage was linked to the particulate fraction, with a definite subsurface minimum at 10 to 15 m. There was a corresponding maximum of a high molecular “non-particulate” thymine-containing fraction at the corresponding depth. From the bottom at 30 m upwards to a…
Die herstellung molekulareinheitlicher leiteroligomerer und einer molekulareinheitlichen hexaacrylsäure. IV. Mitt.: Modelle für matrizenreaktionen
1968
Die phenolischen Hydroxylgruppen molekulareinheitlicher Mehrkernverbindungen mit vier und funf pKresolbausteinen je Molekul konnten vollstandig mit Acrylsaurechlorid in Gegenwart von Triathylamin verestert werden. Lies man auf die in siedendem Benzol stark verdunnten mehrafachen Acrylsaureester einen Uberschus an Radikalen aus α.α′-Azoisobutyrodinitril einwirken, so bildeten sich mit guter Ausbeute molekulareinheitliche, dunnschichtchromatographisch reine Leiteroligomere. Die alkalische Verseifung des Leiteroilgomeren mit vier p-Kresolbausteinen gab eine molekulareinheitliche Hexaacrylsaure, die als Hexamethylester durch Elementaranalyse und Molekulargewicht charakterisiert wurde; die gefun…
Studies on the synthesis of heterocyclic compounds. Part VI. The action of methyl salicylate on some 5-aminopyrazoles
1981
Some 1-phenyl-3-R-5-aminopyrazoles reacted with methyl salicylate to give N-(1-phenyl-3-R-pyrazol-5-yl)-2-methoxybenzamides (3a,b,c), 1-phenyl-2-methyl-3-R-salicyloilimino-3-pyrazolines (4a,b,c) together with 1-phenyl-3-R-5-methylamino pyrazoles (5a,b,c). The structures of the new compounds 3 and 4 were determined on the basis of analytical and spectroscopic data as well as on the acid hydrolysis products.
Polycondensed nitrogen heterocycles. Part25. Aminopyrrolo[1,2-f]-phenanthridines by decomposition of 2-(3-azidophenyl)-1-arylpyrroles
1994
Acid catalyzed decomposition of the azido derivatives 4a-c gave rise to amino-hydroxy-phenylpyrroles of type 7 and 8 upon hydrolysis of the intermediate aryl nitrenium ions, together with the hydrogen abstraction compounds of type 3. The aminopyrrolo[1,2-f]phenanthridines 10, 11, and 12 were obtained by treatment with TFMSA of the azide 4d in which the ring being attacked was made more nucleophilic by the introduction of the methoxy group.