Reductive amination Dotaz Zobrazit nápovědu
In this work, we compare labeling by two negatively charged fluorescent labels, 8-aminopyrene-1,3,6-trisulfonic acid (APTS) and 8-(2-hydrazino-2-oxoethoxy)pyrene-1,3,6-trisulfonic acid (Cascade Blue hydrazide [CBH]). Effectiveness of the labeling chemistries were investigated by 4-hydroxybenzaldehyde and maltoheptaose followed by LC/UV-MS and CE/LIF analysis, respectively. The reaction yield of APTS labeling was determined to be only ∼10%. This is due to reduction of almost 90% of the analyte by sodium cyanoborohydride to alcohol, which cannot be further labeled via reductive amination. However, the CBH labeling provides ∼90% reaction yield based on the LC/UV-MS measurements. The significantly higher labeling yield was also confirmed by CE/LIF measurements. Finally, the more effective hydrazone formation technique of CBH was characterized and applied for N-linked glycan analysis by CE/LIF.
- MeSH
- aminace MeSH
- chromatografie kapalinová metody MeSH
- elektroforéza kapilární metody MeSH
- fluorescenční barviva chemie MeSH
- hmotnostní spektrometrie metody MeSH
- hydrazony chemie MeSH
- oligosacharidy analýza chemie MeSH
- pyreny chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The optimization of sustainable protocols for reductive amination has been a lingering challenge in green synthesis. In this context, a comparative study of different metal-loaded cross-linked cyclodextrins (CDs) were examined for the microwave (MW)-assisted reductive amination of aldehydes and ketones using either H2 or formic acid as a hydrogen source. The Pd/Cu heterogeneous nanocatalyst based on Pd (II) and Cu (I) salts embedded in a β-CD network was the most efficient in terms of yield and selectivity attained. In addition, the polymeric cross-linking avoided metal leaching, thus enhancing the process sustainability; good yields were realized using benzylamine under H2. These interesting findings were then applied to the MW-assisted one-pot synthesis of secondary amines via a tandem reductive amination of benzaldehyde with nitroaromatics under H2 pressure. The formation of a CuxPdy alloy under reaction conditions was discerned, and a synergic effect due to the cooperation between Cu and Pd has been hypothesized. During the reaction, the system worked as a bifunctional nanocatalyst wherein the Pd sites facilitate the reduction of nitro compounds, while the Cu species promote the subsequent imine hydrogenation affording structurally diverse secondary amines with high yields.
- MeSH
- aminace MeSH
- aminy chemie MeSH
- benzaldehydy chemie MeSH
- beta-cyklodextriny chemie MeSH
- cyklodextriny chemie MeSH
- katalýza MeSH
- kovy chemie MeSH
- měď chemie MeSH
- mikrovlny * MeSH
- nanočástice chemie MeSH
- palladium chemie MeSH
- reagencia zkříženě vázaná chemie MeSH
- Publikační typ
- časopisecké články MeSH
Capillary electrophoresis-mass spectrometry was applied for the analysis of oligosaccharides and N-linked glycans with an attached charge label facilitating electrophoretic migration and electrospray ionization efficiency. Several different labeling strategies have been tested with different tags and tagging reactions including reductive amination and hydrazone formation. However, a formation of multiple labeled N-linked glycans was observed by CE-MS in a positive ion mode when positively charged labels such as aliphatic amines containing a quaternary ammonium group were attached to N-linked glycans by reductive amination. A reaction mechanism explaining a side reaction occurring during the labeling and the multiple product formation was proposed and confirmed by using isotopically labeled N-acetylglucosamine. Finally, it was confirmed that derivatization of sugars via a hydrazone formation can be a simpler method with a high reaction yield suitable for high sensitive CE-ESI/MS analyses of N-linked glycans.
The catalytic reaction of copper amine oxidase proceeds through a ping-pong mechanism comprising two half-reactions. In the initial half-reaction, the substrate amine reduces the Tyr-derived cofactor, topa quinone (TPQ), to an aminoresorcinol form (TPQamr) that is in equilibrium with a semiquinone radical (TPQsq) via an intramolecular electron transfer to the active-site copper. We have analyzed this reductive half-reaction in crystals of the copper amine oxidase from Arthrobacter globiformis. Anerobic soaking of the crystals with an amine substrate shifted the equilibrium toward TPQsq in an "on-copper" conformation, in which the 4-OH group ligated axially to the copper center, which was probably reduced to Cu(I). When the crystals were soaked with substrate in the presence of halide ions, which act as uncompetitive and noncompetitive inhibitors with respect to the amine substrate and dioxygen, respectively, the equilibrium in the crystals shifted toward the "off-copper" conformation of TPQamr. The halide ion was bound to the axial position of the copper center, thereby preventing TPQamr from adopting the on-copper conformation. Furthermore, transient kinetic analyses in the presence of viscogen (glycerol) revealed that only the rate constant in the step of TPQamr/TPQsq interconversion is markedly affected by the viscogen, which probably perturbs the conformational change. These findings unequivocally demonstrate that TPQ undergoes large conformational changes during the reductive half-reaction.
The aim of this paper is to review chromatographic and mass-spectrometric methods and underline the best analytical approaches for successful analysis of various hyaluronic acid species in different types of samples. Hyaluronan-degrading enzymes and chemical depolymerization produce di- or oligosaccharides suitable for hyaluronan quantification or structural characterization of hyaluronan derivatives. Efficient purification and pre-column derivatization of hyaluronan disaccharides by reductive amination allow subnanogram quantification in biological samples. The chromatographic separation is capable to distinguish all glycosaminoglycans disaccharides and to resolve hyaluronan fragments with 2-40 monomers. Using electrospray ionization or matrix assisted laser desorption ionization, hyaluronan fragments up to 8 kDa or 41 kDa, respectively, can be observed. One- or two-dimensional chromatographic separation with higly sensitive mass-spectrometric detection is an indispensable tool for revealing substituent position, extent of modification and substitution patterns of chemically modified hyaluronan derivatives. It is essential for studying structure-biological function relationships of hyaluronan and its derivatives.
A novel modular and practical methodology for preparation of 6-substituted pyridin-3-yl C-nucleosides was developed. The Heck reaction of 2-chloro-5-iodopyridine with a 3'-TBDMS-protected glycal gave a 6-chloropyridin-3-yl nucleoside analogue, which was then desilylated, selectively reduced, and reprotected to give the TBDMS-protected 6-chloropyridin-3-yl C-2'-deoxyribonucleoside as a pure beta-anomer in a total yield of 39% over four steps. This key intermediate was then subjected to a series of palladium-catalyzed cross-coupling reactions, aminations, and alkoxylations to give a series of protected 1beta-(6-alkyl-, 6-aryl-, 6-hetaryl, 6-amino-, and 6-tert-butoxypyridin-3-yl)-2'-deoxyribonucleosides. 6-Unsubstituted pyridin-3-yl C-nucleoside was prepared by catalytic hydrogenation of the chloro derivative and 6-oxopyridine C-nucleoside by treatment of the 6-tert-butoxy derivative with TFA. Deprotection of all the silylated nucleosides by Et3N.3HF gave a series of free C-nucleosides (10 examples).
Solid-phase synthesis of 3,4-dihydro-benzo[e][1,4]diazepin-5-ones with three diversity positions is described. Various primary amines were used as the starting material and immobilized on the polystyrene resin equipped with different acid-labile linkers. Polymer-supported amines were converted to α-aminoketones with the use of their sulfonylation with the 4-nitrobenzensulfonylchoride (4-Nos-Cl) and subsequent alkylation with α-bromoketones. After the cleavage of the 4-Nos group, the corresponding α-aminoketones were acylated with various o-nitrobenzoic acids. Reduction of the nitro group followed by spontaneous on-resin ring closure gave the target immobilized benzodiazepines. After acid-mediated cleavage the products were obtained in very good crude purity and satisfactory yields, which makes the developed method applicable for simple library synthesis of the corresponding derivatives in a combinatorial fashion.
This review deals with the mechanism of the formation of carcinogenic N-nitrosoamines in the production of amine oxides by the oxidation of tertiary amines with hydrogen peroxide. The crucial point is the nature of the nitrogen substrate and nitrosating species as they are not added to the process directly. As the nitrogen substrates, we consider particularly primary and secondary amines. Various structures of the nitrosating agents are discussed, for example nitrogen oxides from the ambient air, corrosion inhibitors in the hydrogen peroxide (e.g. NaNO2) or other side nitroso compounds.
