The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Tanja M Wrodnigg - One of the best experts on this subject based on the ideXlab platform.
-
new lectin ligands testing of Amadori Rearrangement products with a series of mannoside specific lectins
Carbohydrate Research, 2019Co-Authors: Herwig Prasch, Cornelia Hojnik, Thisbe K Lindhorst, Blanka Didak, Ludovic Landemarre, Tanja M WrodniggAbstract:Abstract 1-(N-Phenyl)amino-1-deoxy-α-D-manno-hept-2-ulose (2) and two multivalent BSA-based structures 7 and 8, d -manno-configured C-glycosyl-type compounds derived from an Amadori Rearrangement, were evaluated as ligands for mannoside-specific lectins of various sources. The determination of the concentration corresponding to 50% of inhibition (IC50) is described. Multivalency turned out to effectively influence ligand selectivity and lectin binding.
-
the Amadori Rearrangement for carbohydrate conjugation scope and limitations
European Journal of Organic Chemistry, 2016Co-Authors: Cornelia Hojnik, Anne Muller, Tobiaselias Gloe, Thisbe K Lindhorst, Tanja M WrodniggAbstract:The Amadori Rearrangement was investigated for the synthesis of C-glycosyl-type neoglycoconjugates. Various amines including diamines, amino-functionalized glycosides, lysine derivatives, and peptides were conjugated with two different heptoses to generate non-natural C-glycosyl-type glycoconjugates of the d-gluco and d-manno series. With these studies, the scope and limitations of the Amadori Rearrangement as a conjugation method have been exemplified with respect to the carbohydrate substrate, as well as the amino components.
-
Are D-manno-configured Amadori products ligands of the bacterial lectin FimH?
Beilstein Journal of Organic Chemistry, 2015Co-Authors: Tobiaselias Gloe, Cornelia Hojnik, Tanja M Wrodnigg, Insa Stamer, Thisbe K LindhorstAbstract:The Amadori Rearrangement was employed for the synthesis of C-glycosyl-type D-mannoside analogues, namely 1-propargylamino- and 1-phenylamino-1-deoxy-α-D-manno-heptopyranose. They were investigated as ligands of type 1-fimbriated E. coli bacteria by means of molecular docking and bacterial adhesion studies. It turns out that Amadori Rearrangement products have a limited activity as inhibitors of bacterial adhesion because the β-C-glycosidically linked aglycone considerably hampers complexation within the carbohydrate binding site of the type 1-fimbrial lectin FimH.
-
the Amadori Rearrangement as glycoconjugation method synthesis of non natural c glycosyl type glycoconjugates
Beilstein Journal of Organic Chemistry, 2012Co-Authors: Katharina Gallas, Gerit Pototschnig, Florian Adanitsch, Arnold E Stutz, Tanja M WrodniggAbstract:The Amadori Rearrangement was investigated as a potential method for the conjugation of carbohydrate moieties to suitable amino components. Starting from selected aldoheptoses, which are readily available by means of the Kiliani–Fischer C-elongation reaction of the corresponding aldohexoses, glycoconjugates presenting D-gluco, D-manno and D-galacto as well as GlcNAc motifs have been synthesised. Following this strategy, non-natural C-glycosyl type glycoconjugates, which can be utilised as building blocks for the composition of larger molecular constructions, are available by a very short synthetic approach.
-
the Amadori Rearrangement as key reaction for the synthesis of neoglycoconjugates
Carbohydrate Research, 2008Co-Authors: Tanja M Wrodnigg, Christiane Kartusch, Carina IllaszewiczAbstract:Abstract The Amadori Rearrangement was introduced as a key step for the conjugation of carbohydrate moieties with suitable amines such as aliphatic amines and amino acid derivatives. The Rearrangement products were further transformed into the corresponding 1- N ,2- O cyclic carbamates employing triphosgene to obtain anomerically stable glycoconjugates. The reaction conditions were probed on a model substrate, 3,5-di- O -benzyl-α,β- d -glucofuranose and further applied to d - glycero - d - gulo -heptose, which gave ‘ d - gluco- conjugates’ in the α-anomeric form exclusively in high isolated yields.
Lothar W Kroh - One of the best experts on this subject based on the ideXlab platform.
-
simultaneous formation of 3 deoxy d threo hexo 2 ulose and 3 deoxy d erythro hexo 2 ulose during the degradation of d glucose derived Amadori Rearrangement products mechanistic considerations
Carbohydrate Research, 2018Co-Authors: Martin Kaufmann, Clemens Mugge, Sophie Kruger, Lothar W KrohAbstract:Abstract Analyzing classical model reaction systems of Amadori Rearrangement products (ARP) it became apparent that the formation of 3-deoxy- d -threo-hexo-2-ulose (3-deoxygalactosone, 3-DGal) during the degradation of ARPs is highly dependent on pH and the amino acid residue of the respective ARP. Based on a detailed analysis of the NMR chemical shifts of the sugar moieties of different ARPs, it could be derived that the formation of 3-DGal is sensitive to the stability of a co-operative hydrogen bond network which involves HO-C3, the deprotonated carboxyl functionality and the protonated amino nitrogen of the amino acid substituent. Participating in this bond network, HO-C3 is partially protonated which facilitates the elimination of water at C3. Based on that, a new mechanism of 3-deoxyglycosone formation is proposed.
-
structure reactivity relationship of Amadori Rearrangement products compared to related ketoses
Carbohydrate Research, 2016Co-Authors: Martin Kaufmann, Philipp M Meissner, Daniel Pelke, Clemens Mugge, Lothar W KrohAbstract:Structure-reactivity relationships of Amadori Rearrangement products compared to their related ketoses were derived from multiple NMR spectroscopic techniques. Besides structure elucidation of six Amadori Rearrangement products derived from d-glucose and d-galactose with l-alanine, l-phenylalanine and l-proline, especially quantitative (13)C selective saturation transfer NMR spectroscopy was applied to deduce information on isomeric systems. It could be shown exemplarily that the Amadori compound N-(1-deoxy-d-fructos-1-yl)-l-proline exhibits much higher isomerisation rates than d-fructose, which can be explained by C-1 substituent mediated intramolecular catalysis. In combination with a reduced carbonyl activity of Amadori compounds compared to their related ketoses which results in an increased acyclic keto isomer concentration, the results on isomerisation dynamics lead to a highly significant increased reactivity of Amadori compounds. This can be clearly seen, comparing approximated carbohydrate milieu stability time constants (ACuSTiC) which is 1 s for N-(1-deoxy-d-fructos-1-yl)-l-proline and 10 s for d-fructose at pD 4.20 ± 0.05 at 350 K. In addition, first NMR spectroscopic data are provided, which prove that α-pyranose of (amino acid substituted) d-fructose adopts both, (2)C5 and (5)C2 conformation.
-
Structure–reactivity relationship of Amadori Rearrangement products compared to related ketoses
Carbohydrate Research, 2016Co-Authors: Martin Kaufmann, Philipp M Meissner, Daniel Pelke, Clemens Mugge, Lothar W KrohAbstract:Abstract Structure-reactivity relationships of Amadori Rearrangement products compared to their related ketoses were derived from multiple NMR spectroscopic techniques. Besides structure elucidation of six Amadori Rearrangement products derived from d -glucose and d -galactose with l -alanine, l -phenylalanine and l -proline, especially quantitative 13C selective saturation transfer NMR spectroscopy was applied to deduce information on isomeric systems. It could be shown exemplarily that the Amadori compound N-(1-deoxy- d -fructos-1-yl)- l -proline exhibits much higher isomerisation rates than d -fructose, which can be explained by C-1 substituent mediated intramolecular catalysis. In combination with a reduced carbonyl activity of Amadori compounds compared to their related ketoses which results in an increased acyclic keto isomer concentration, the results on isomerisation dynamics lead to a highly significant increased reactivity of Amadori compounds. This can be clearly seen, comparing approximated carbohydrate milieu stability time constants (ACuSTiC) which is 1 s for N-(1-deoxy- d -fructos-1-yl)- l -proline and 10 s for d -fructose at pD 4.20 ± 0.05 at 350 K. In addition, first NMR spectroscopic data are provided, which prove that α-pyranose of (amino acid substituted) d -fructose adopts both, 2C5 and 5C2 conformation.
-
Degradation of Oligosaccharides in Nonenzymatic Browning by Formation of α-Dicarbonyl Compounds via a “Peeling Off” Mechanism
Journal of Agricultural and Food Chemistry, 2000Co-Authors: Anke Hollnagel, Lothar W KrohAbstract:The formation of α-dicarbonyl-containing substances and Amadori Rearrangement products was studied in the glycine-catalyzed (Maillard reaction) and uncatalyzed thermal degradation of glucose, maltose, and maltotriose using o-phenylenediamine as trapping agent. Various degradation products, especially α-dicarbonyl compounds, are formed from carbohydrates with differing degrees of polymerization during nonenzymatic browning. The different Amadori Rearrangement products, isomerization products, and α-dicarbonyls produced by the used carbohydrates were quantified throughout the observed reaction time, and the relevance of the different degradation pathways is discussed. In the Maillard reaction (MR) the amino-catalyzed Rearrangement with subsequent elimination of water predominated, giving rise to hexosuloses with α-dicarbonyl structure, whereas under caramelization conditions more sugar fragments with an α-dicarbonyl moiety were formed. For the MR of oligosaccharides a mechanism is proposed in which 1,4-dide...
Martin Kaufmann - One of the best experts on this subject based on the ideXlab platform.
-
simultaneous formation of 3 deoxy d threo hexo 2 ulose and 3 deoxy d erythro hexo 2 ulose during the degradation of d glucose derived Amadori Rearrangement products mechanistic considerations
Carbohydrate Research, 2018Co-Authors: Martin Kaufmann, Clemens Mugge, Sophie Kruger, Lothar W KrohAbstract:Abstract Analyzing classical model reaction systems of Amadori Rearrangement products (ARP) it became apparent that the formation of 3-deoxy- d -threo-hexo-2-ulose (3-deoxygalactosone, 3-DGal) during the degradation of ARPs is highly dependent on pH and the amino acid residue of the respective ARP. Based on a detailed analysis of the NMR chemical shifts of the sugar moieties of different ARPs, it could be derived that the formation of 3-DGal is sensitive to the stability of a co-operative hydrogen bond network which involves HO-C3, the deprotonated carboxyl functionality and the protonated amino nitrogen of the amino acid substituent. Participating in this bond network, HO-C3 is partially protonated which facilitates the elimination of water at C3. Based on that, a new mechanism of 3-deoxyglycosone formation is proposed.
-
structure reactivity relationship of Amadori Rearrangement products compared to related ketoses
Carbohydrate Research, 2016Co-Authors: Martin Kaufmann, Philipp M Meissner, Daniel Pelke, Clemens Mugge, Lothar W KrohAbstract:Structure-reactivity relationships of Amadori Rearrangement products compared to their related ketoses were derived from multiple NMR spectroscopic techniques. Besides structure elucidation of six Amadori Rearrangement products derived from d-glucose and d-galactose with l-alanine, l-phenylalanine and l-proline, especially quantitative (13)C selective saturation transfer NMR spectroscopy was applied to deduce information on isomeric systems. It could be shown exemplarily that the Amadori compound N-(1-deoxy-d-fructos-1-yl)-l-proline exhibits much higher isomerisation rates than d-fructose, which can be explained by C-1 substituent mediated intramolecular catalysis. In combination with a reduced carbonyl activity of Amadori compounds compared to their related ketoses which results in an increased acyclic keto isomer concentration, the results on isomerisation dynamics lead to a highly significant increased reactivity of Amadori compounds. This can be clearly seen, comparing approximated carbohydrate milieu stability time constants (ACuSTiC) which is 1 s for N-(1-deoxy-d-fructos-1-yl)-l-proline and 10 s for d-fructose at pD 4.20 ± 0.05 at 350 K. In addition, first NMR spectroscopic data are provided, which prove that α-pyranose of (amino acid substituted) d-fructose adopts both, (2)C5 and (5)C2 conformation.
-
Structure–reactivity relationship of Amadori Rearrangement products compared to related ketoses
Carbohydrate Research, 2016Co-Authors: Martin Kaufmann, Philipp M Meissner, Daniel Pelke, Clemens Mugge, Lothar W KrohAbstract:Abstract Structure-reactivity relationships of Amadori Rearrangement products compared to their related ketoses were derived from multiple NMR spectroscopic techniques. Besides structure elucidation of six Amadori Rearrangement products derived from d -glucose and d -galactose with l -alanine, l -phenylalanine and l -proline, especially quantitative 13C selective saturation transfer NMR spectroscopy was applied to deduce information on isomeric systems. It could be shown exemplarily that the Amadori compound N-(1-deoxy- d -fructos-1-yl)- l -proline exhibits much higher isomerisation rates than d -fructose, which can be explained by C-1 substituent mediated intramolecular catalysis. In combination with a reduced carbonyl activity of Amadori compounds compared to their related ketoses which results in an increased acyclic keto isomer concentration, the results on isomerisation dynamics lead to a highly significant increased reactivity of Amadori compounds. This can be clearly seen, comparing approximated carbohydrate milieu stability time constants (ACuSTiC) which is 1 s for N-(1-deoxy- d -fructos-1-yl)- l -proline and 10 s for d -fructose at pD 4.20 ± 0.05 at 350 K. In addition, first NMR spectroscopic data are provided, which prove that α-pyranose of (amino acid substituted) d -fructose adopts both, 2C5 and 5C2 conformation.
Seetharama A Acharya - One of the best experts on this subject based on the ideXlab platform.
-
Catalytic Aspects of the Glycation Hot Spots of Proteins
Maillard reactions in chemistry food and health, 2020Co-Authors: Seetharama A Acharya, Parimala NacharajuAbstract:Summary A systematic investigation of the protein structural factors that could determine the chemical reactivity of the amino groups of proteins for nonenzymic glycation (glycation hot spots) has been carried out. The studies suggest that the microdomains of the glycation hot spots of proteins are Amadori Rearrangement catalytic centers. The isomerization reaction catalysed by these microdomains is comparable to the reactions catalyzed by glucose isomerase and triose phosphate isomerase. The protein microdomains containing a constellation of positively charged functional groups thereby generating a proton rich microenvironment seem to act as the Amadori Rearrangement catalytic centers. The α and/or the e-amino groups located in such microdomains and accessible to aldoses to form the aldimine adducts are the glycation hot spots of proteins. It is suggested that the catalytic power of the glycation hot spots of proteins may have some role in the post glycation reactions leading to the generation of the advanced glycation end products and thus in the pathophysiology of diabetes.
-
Amadori Rearrangement potential of hemoglobin at its glycation sites is dependent on the three dimensional structure of protein
Biochemistry, 1992Co-Authors: Parimala Nacharaju, Seetharama A AcharyaAbstract:The site selectivity of nonenzymic glycation of proteins has been suggested to be a consequence of the Amadori Rearrangement activity of the protein at the respective glycation sites. The catalytic activity that determines the potential of a site for nonenzymic glycation is the propensity of its microenvironment to isomerize the protein bound aldose (aldimine) to a protein bound ketose (ketoamine)
-
aldimine to ketoamine isomerization Amadori Rearrangement potential at the individual nonenzymic glycation sites of hemoglobin a preferential inhibition of glycation by nucleophiles at sites of low isomerization potential
Journal of Protein Chemistry, 1991Co-Authors: Seetharama A Acharya, Bhuvaneshwari DoraiAbstract:The relative roles of the two structural aspects of nonenzymic glycation sites of hemoglobin A, namely the ease with which the amino groups could form the aldimine adducts and the propensity of the microenvironments of the respective aldimines to facilitate the Amadori Rearrangement, in dictating the site selectivity of nonenzymic glycation with aldotriose has been investigated. The chemical reactivity of the amino groups of hemoglobin A forin vitro reductive glycation with aldotriose is distinct from that in the nonreductive mode. The reactivity of amino groups of hemoglobin A toward reductive glycation (i.e., propensity for aldimine formation) decreases in the order Val-1(β), Val-1(α), Lys-66(β), Lys-61(α), and Lys-16(α). The overall reactivity of hemoglobin A toward nonreductive glycation decreased in the order Lys-16(α), Val-1(β), Lys-66(β), Lys-82(β), Lys-61(α), and Val-1(α). Since the aldimine is the common intermediate for both the reductive and nonreductive modification, the differential selectivity of protein for the two modes of glycation is clearly a reflection of the propensity of the microenvironments of nonenzymic glycation sites to facilitate the isomerization reaction (i.e., Amadori Rearrangement). A semiquantitative estimate of this propensity of the microenvironment of the nonenzymic glycation sites has been obtained by comparing the nonreductive (nonenzymic) and reductive modification at individual glycation sites. The microenvironment of Lys-16(α) is very efficient in facilitating the Rearrangement and the relative efficiency decreases in the order Lys-16(α), Lys-82(β), Lys-66(β), Lys-61(α), Val-1(β), and Val-1(α). The propensity of the microenvironment of Lys-16(α) to facilitate the Amadori Rearrangement of the aldimine is about three orders of magnitude higher than that of Val-1(α) and is about 50 times higher than that of Val-1(β). The extent of nonenzymic glycation at the individual sites is modulated by various factors, such as thepH, concentration of aldotriose, and the concentration of the protein. The nucleophiles—such as tris, glycine ethyl ester, and amino guanidine—inhibit the glycation by trapping the aldotriose. The nonenzymic glycation inhibitory power of nucleophile is directly related to its propensity to form aldimine. Thus, the extent of inhibition of nonenzymic glycation at a given site by a nucleophile directly reflects the relative role ofpKa of the site in dictating the glycation at that site. The nonenzymic glycation of an amino group of a protein is an additive/synergestic consequence of the propensity of the site to form aldimine adducts on one hand, and the propensity of its microenvironment to facilitate the isomerization of the aldimines to ketoamines on the other. The isomerization potential of microenvironment plays the dominant role in dictating the site specificity of the nonenzymic glycation of proteins.
Steven G Withers - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of 1 amino 1 2 5 trideoxy 2 5 imino d mannitol a novel analogue of the powerful glucosidase inhibitor 2 5 dideoxy 2 5 imino d mannitol via an Amadori Rearrangement of 5 azido 5 deoxy d glucofuranose
Tetrahedron Letters, 1997Co-Authors: Tanja M Wrodnigg, Arnold E Stutz, Steven G WithersAbstract:Abstract By an Amadori Rearrangement of easily available 5-azido-5-deoxy- d -glucofuranose with dibenzylamine and subsequent catalytic hydrogenation of the resulting 5-azido-1-dibenzylamino-1,5-dideoxy- d -fructopyranose, the new 1-amino-1,2,5-trideoxy-2,5-imino- d -mannitol was obtained in only two steps and excellent overall yield. Likewise, other amines and/or other 5-modified hexofuranoses can be used to advantage. The reported Rearrangement reaction is a high yielding, convenient and apparently general entry to 1-aminodeoxyketopyranoses modified at C-5, facilitated by the ring enlargement of the aldofuranose to the ketopyranose as an additional driving force.
