Showing papers on "Pyranose published in 1996"
TL;DR: The endoglucanase I complex with the thiosaccharide substrate analogue clearly illustrates the potential of nonhydrolyzable sulfur-linked oligosaccharides in the elucidation of substrate binding and catalysis by glycosyl hydrolases.
Abstract: Endoglucanase I (EG I) is a cellulase, from glycosyl hydrolase family 7, which cleaves the β-1,4 linkages of cellulose with overall retention of configuration. The structure of the EG I from Fusarium oxysporum, complexed to a nonhydrolyzable thiooligosaccharide substrate analogue, has been determined by X-ray crystallography at a resolution of 2.7 A utilizing the 4-fold noncrystallographic symmetry present in the asymmetric unit. The electron density map clearly reveals the presence of three glucosyl units of the inhibitor, consistent with the known number of sugar-binding subsites, located at the active site of the enzyme in the −2, −1, and +1 subsites, i.e., actually spanning the point of enzymatic cleavage. The pyranose ring at the point of potential enzymatic cleavage is clearly distorted from the standard 4C1 chair as was originally suggested for β-retaining enzymes by Phillips [Ford, L. O., Johnson, L. N., Machin, P. A., Phillips, D. C., & Tijan, T. (1974) J. Mol. Biol. 88, 349−371]. The distortion ...
214 citations
TL;DR: Five different SAAs have been synthesized that show the ability to constrain linear backbone conformations or distinct turn structures and NMR studies provide evidence for the conformation-inducing effect of the carbohydrate moiety.
Abstract: Sugar amino acids (SAAs) were designed and synthesized as new non-peptide peptidomimetics utilizing carbohydrates as peptide building blocks. They represent sugar-like ring structures that carry an amino and a carboxylic functional group and have a specific conformational influence on the backbone of peptides due to their distinct substitution patterns in rigid pyranose sugar rings. Five different SAAs (SAA1α, SAA1β, SAA2, SAA3, and SAA4) have been synthesized that show the ability to constrain linear backbone conformations or distinct turn structures. Linear and cyclic peptides involving SAAs have been prepared in solution as well as by solid phase synthesis. SAA1α and SAA2 were incorporated into two linear Leu-enkephalin analogs, replacing the natural Gly-Gly dipeptide. NMR studies provide evidence for the conformation-inducing effect of the carbohydrate moiety. SAA2 and SAA3 have been placed in cyclic hexapeptide analogs of somatostatin; SAA4 was incorporated in a model peptide. The conformation of the...
163 citations
TL;DR: The three-dimensional structure of the C-type carbohydrate-recognition domain (CRD) of MBP-C using x-ray crystallography explains how MBPs recognize a wide range of monosaccharides and suggest how fine specificity differences betweenMBP-A and MBPC may be achieved.
156 citations
TL;DR: The spirocyclization reaction has been accomplished from a conveniently homologated carbohydrate by an intramolecular hydrogen abstraction reaction promoted by alkoxy radicals as discussed by the authors, which has been obtained from carbohydrates in pyranose or furanose forms.
85 citations
TL;DR: A model in which CBDN1 interacts with soluble cellooligosaccharides and, by inference, with single polysaccharide chains in regions of amorphous cellulose is led to, primarily through hydrogen bonding to the equatorial hydroxyl groups of the pyranose rings.
Abstract: The N-terminal cellulose-binding domain (CBDN1) from Cellulomonas fimi beta-1,4-glucanase CenC binds amorphous but not crystalline cellulose. To investigate the structural and thermodynamic bases of cellulose binding, NMR and difference ultraviolet absorbance spectroscopy were used in parallel with calorimetry (Tomme, P., Creagh, A. L., Kilburn, D. G., & Haynes, C. A., (1996) Biochemistry 35, 13885-13894) to characterize the interaction of soluble cellooligosaccharides with CBDN1. Association constants, determined from the dependence of the amide 1H and 15N chemical shifts of CBDN1 upon added sugar, increase from 180 +/- 60 M-1 for cellotriose to 4,200 +/- 720 M-1 for cellotetraose, 34,000 +/- 7,600 M-1 for cellopentaose, and an estimate of 50,000 M-1 for cellohexaose. This implies that the CBDN1 cellulose-binding site spans approximately five glucosyl units. On the basis of the observed patterns of amide chemical shift changes, the cellooligosaccharides bind along a five-stranded beta-sheet that forms a concave face of the jelly-roll beta-sandwich structure of CBDN1. This beta-sheet contains a strip of hydrophobic side chains flanked on both sides by polar residues. NMR and difference ultraviolet absorbance measurements also demonstrate that tyrosine, but not tryptophan, side chains may be involved in oligosaccharide binding. These results lead to a model in which CBDN1 interacts with soluble cellooligosaccharides and, by inference, with single polysaccharide chains in regions of amorphous cellulose, primarily through hydrogen bonding to the equatorial hydroxyl groups of the pyranose rings. Van der Waals stacking of the sugar rings against the apolar side chains may augment binding. CBDN1 stands in marked contrast to previously characterized CBDs that absorb to crystalline cellulose via a flat binding surface dominated by exposed aromatic rings.
74 citations
TL;DR: The results of this study indicate that 9-O-acetylation at the terminal sialic acid does not influence the overall conformation of the ganglioside, and binding of GD1a (eNeu5,9Ac2) to proteins should thus at least partially be mediated by the presence of this group.
Abstract: The influence of 9-O-acetylation of GD1a, yielding GD1a (eNeu5,9Ac2) with a 9-O-acetylated sialic acid moiety linked to the outer galactose residue, on the spatial extension and mobility of the carbohydrate chain and on recognition by a natural human antibody is analysed. To study a potential impact of the O-acetyl group on the overall conformation of the carbohydrate chain, molecular dynamics (MD) simulations of oligosaccharide chain fragments of increasing length starting from the non-reducing end have been carried out for the first time in this study. They revealed a considerable loss in chain flexibility after addition of the internal N-acetylneuraminic acid onto the chain. Besides MD calculations with different dielectric constants, the conformational behaviour of the complete oligosaccharide chain of the 9-O-acetylated GD1a ganglioside was simulated in the solvents water and dimethyl sulfoxide. These solvents were also used in NMR measurements. The results of this study indicate that 9-O-acetylation at the terminal sialic acid does not influence the overall conformation of the ganglioside. An extended interaction analysis of energetically minimized conformations of GD1a (eNeu5,9Ac2) and GD1a, obtained during molecular dynamics simulations, allowed assessment of the influence of the different parts of the saccharide chains on spatial flexibility. Noteworthy energetic interactions, most interestingly between the 9-O-acetyl group and the pyranose ring of N-acetylgalactosamine, were ascertained by the calculations. However, the strength of this interaction does not force the ganglioside into a conformation, where the 9-O-acetyl group is no longer accessible. Binding of GD1a (eNeu5,9Ac2) to proteins, which are specific for 9-O-acetylated sialic acids, should thus at least partially be mediated by the presence of this group. To experimentally prove this assumption, a NMR study of 9-O-acetylated GD1a in the presence of an affinity-purified polyclonal IgG fraction from human serum with preferential binding to 9-O-acetylated sialic acid was performed. The almost complete disappearance of the intensity of the 9-O-acetyl methyl signal of the GD1a (eNeu5,9Ac2) clearly indicates that the assumed interaction of the 9-O-acetyl group with the human protein takes place.
49 citations
TL;DR: In this article, the thermal decomposition of polyurethanes derived from mono-and disaccharides and their raw materials was investigated in order to investigate the thermodynamic decomposition mechanism.
36 citations
TL;DR: In this paper, a multinuclear 1D and 2D NMR study of d -galacturonic and d -glucuronic acids in aqueous solution and their complexation with tungstate and molybdate ions for variable concentration and pH conditions has been undertaken.
33 citations
32 citations
TL;DR: In this paper, 2-Fluoro-2-deoxy-γ-xylonic and -lyxonic lactones, 7a and 7b, were prepared via diastereoselective fluorination of the α,β-unsaturated chiral imide 5 followed by dihydroxylation.
30 citations
TL;DR: In this article, a simple, high-yielding three-step procedure to convert unprotected carbohydrates into N-allylglycosides was described, which allowed the reducing-end pyranose ring to remain intact.
Abstract: Synthetic, multivalent, carbohydrate assemblies are important tools in studying the avidity of many naturally occuring lectins for their ligands. This report details a simple, high-yielding three-step procedure to convert unprotected carbohydrates into N-allylglycosides. This method compliments the reductive amination procedure but allows the reducing-end pyranose ring to remain intact. No carbohydrate protecting groups are needed, and the resulting N-allylglycosylamide can be easily linked to other molecules. Two examples of analogs of silyl Lewisx and sulfo Lewisx have been derivatized by this process.
TL;DR: The aminoheptose destomic acid (3.5) and the aminooctose lincosamine (6.8) were synthesized in protected form by parallel sequences starting from the oxazolidine derivatives 2.4 and 5.6.
Abstract: The aminoheptose destomic acid (3.5) and the aminooctose lincosamine (6.8) were synthesized in protected form by parallel sequences starting from the oxazolidine derivatives 2.4 and 5.1 of N-CBz serinal and N-BOC threoninal. The parallel sequences feature BF3-promoted addition of the (R)-γ-OTBS allylic stannane 2.8 to the homologated enals 2.7 and 5.4, respectively, followed by stereoselective bis-dihydroxylation of the derived bis-OTBS ethers 2.10 and 5.6. Regioselective oxidative cleavage of the less hindered vicinal diol moieties of these intermediates led to the γ-lactols 3.2 and 5.8, respectively. In the former case, treatment with TBAF and subsequent hydrolysis removed the OTBS and acetonide protecting groups affording the destomic acid precursor, pyranose 3.4. Lactol 5.8 was converted to the pyranoside 6.3 by silyl ether cleavage, acidic hydrolysis, and bis-acetonide formation. Inversion of the C7 hydroxyl grouping was effected by the Mitsunobu methodology with p-NO2C6H4CO2H. Subsequent hydrolysis,...
TL;DR: In this article, an attempt at Pauson-Khand cyclisation of exo-methylene carbohydrate enynic substrates is described, and a 3-Exo methylene derivative cyclises to give a normal Pausone-khand product, while cyclization of a 4-ExO methylene analog follows a previously unreported pathway to give fused bicycloheptene -pyranose tricyclic product.
TL;DR: This work reacted N,N-diethyl-2-(dimethylsulfuranylidene)acetamide with 4,6-O-alkylidene-glycopyranoses under several experimental conditions and obtained derivatives of acyclic 3-(polyhydroxyalkyl)-alpha,beta-epoxyamides, which are highly functionalized acyClic structures starting from easily obtained cyclohemiacetalic monosaccharides.
Abstract: We reacted N,N-diethyl-2-(dimethylsulfuranylidene)acetamide with 4,6-O-alkylidene-glycopyranoses under several experimental conditions and obtained, stereoselectively, derivatives of acyclic 3-(polyhydroxyalkyl)-α,β-epoxyamides. In this way, and in one stage, we introduced, highly stereoselectively, two new chiral carbons with a substituted asymmetric epoxide group that could then be regioselectively transformed and, in addition, obtained highly functionalized acyclic structures starting from easily obtained cyclohemiacetalic monosaccharides. The configuration of the new chiral carbons of the resulting trans-epoxyamides was determined by comparing the IR, NMR, and polarimetric data with another epoxyamide of known configuration. We attempted to explain the stereochemistry of the major products by proposing a preferential conformation for the different starting aldehyde sugars in the basic reaction medium that took into account, at first, the principal electrical interactions between the carbonyl group and...
TL;DR: In this paper, a new method for the synthesis of 4-amino-D-hex-2-enopyranosides and 2-AMINO-Dhexhex-3-ENOPYRANSIDE was developed.
Abstract: A new method for the synthesis of 4-amino-D-hex-2-enopyranosides and 2-amino-D-hex-3-enopyranosides has been developed. The key feature in this method involves construction of the allylamine moiety in the pyranose framework by employing an allyl cyanate-to-isocyanate rearrangement.
TL;DR: In this paper, a novel route to asymmetric formation of tertiary chiral centres of sugars via 2,2′-spirocyclopropane derivatives has been described, which forms the basis of the proposed synthesis of the C18C23 subunit of lasonolide A.
TL;DR: The crystal structures and thermal properties of methyl 6-O-n-decanoyl-α-D-glucopyranoside (1), methyl 6 O-ndodecanoyls-β-Dglucophyranosides (2, 3, 4, 5, 6, 7.5, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 34, 35, 34
Abstract: The crystal structures and thermal properties of methyl 6-O-n-decanoyl-α-D-glucopyranoside (1), methyl 6-O-n-dodecanoyl-α-D-glucopyranoside (2), methyl 6-O-n-dodecanoyl-β-D-glucopyranoside (3), and methyl 6-O-n-dodecanoyl-α-D-galactopyranoside (4) were studied by X-ray and thermal analysis. Anhydrous crystals obtained from methanol solution by slow evaporation are monoclinic and in space group P2 1 with Z = 2. Cell dimensions : 1, a = 4.967(1) A, b = 7.513(1) A, c = 25.917(2) A, β = 92.92(1)° ; 2, a = 4.968(1) A, b = 7.503(1) A, c = 28.443(2) A, β = 92.68(1)° ; 3, a = 7.722(1) A, b = 7.346(1) A,c = 18.626(2) A, β = 91.51(1)° ; 4, a = 5.760(1) A, b = 7.986(1) A, c = 23.339(1) A, β = 90.21(1)°. The sugar moieties of 1 and 2 are disordered. The pyranose rings of β-D-glucopyranoside and α-D-galactopyranoside in 3 and 4, respectively, are in 4 C 1 chair conformation, and the alkyl chains in 1-4 are all-trans. Molecules are arranged in a bilayer structure with interdigitated alkyl chains. The hydrogen bonds between sugar moieties in 3 and 4, which are found only between adjacent layers, form infinite and finite chains in respective crystals. The melting point of compounds which have the same alkyl chain length are 70.1, 93.5, and 137.8°C for 2, 3, and 4, respectively. Epimers of these molecules exhibit packing arrangements which explain the wide variety in their melting temperatures.
TL;DR: Aldopyranosuronic and aldofurano-nasuronic acid lactones with one carbon less were obtained when hexuronic acids in pyranose or furanose forms undergo a tandem β-fragmentation-cyclization reaction promoted by the system (diacetoxyiodo)benzene-iodine, under mild conditions.
TL;DR: In particular, the authors showed that 1,2-bis( trimethylsilyloxy )ethane gave 6-chloro-6-deoxy-1,1-ethylenedioxy-2,3,4-tri-O-methyl-D-glucopyranose (23a) conversion of the corresponding 6-iodo compound (23b) and treatment of this with 1,8-diazabicyclo[5.4.3.1] gave (1R,6S,7R,8
Abstract: Hydrolysis of methyl 6-chloro-6-deoxy-2,3,4-tri-O-methyl-α-D-glucopyranoside (19b) and Swern oxidation of the resulting anomeric hemiacetals (20) gave 6-chloro-6-deoxy-2,3,4-tri-O-methyl-D-glucono-1,5-lactone (21), treatment of which with 1,2-bis( trimethylsilyloxy )ethane in the presence of trimethylsilyl trifluoromethanesulfonate gave 6-chloro-1,6-dideoxy-1,1-ethylenedioxy-2,3,4-tri-O-methyl-D-glucopyranose (23a). Conversion of (23a) into the corresponding 6-iodo compound (23b) and treatment of this with 1,8-diazabicyclo[5.4.0]undec-7-ene afforded the enolic ortho ester 1,6-dideoxy-1,1-ethylenedioxy-2,3,4-tri-O-methyl-D-xylo-hex-5-enopyranose (26). Reaction of (26) with methylmagnesium iodide, or with titanium tetrachloride, gave (1R,6S,7R,8R,9S)-7,8,9-trimethoxy-6-methyl-2,5-dioxabicyclo[4.3.1]decan-1-ol (34), or (2S,3R,4R)-5,5-ethylenedioxy-2,3,4-trimethoxycyclohexanone (28), respectively.
TL;DR: In this article, the synthesis of 3′-deoxy-3′-C -hydroxymethyl branched nucleosides with α- l -lyxopyranosyl and α - l -threofuranosyl sugar moleties is described.
TL;DR: In this paper, the X-ray crystal structure of spirohydantoins of glucofuranose to pyranose isomers was established, and a novel rearrangement was observed of a Gluco-Furanose spiro-hydantoin to an isomeric oxazolidinone, (3 aR,4′ R,5 S,6 S,6 aR )-5-(2′,2′-dimethyl-1′,3′-dioxolane-4′-yl)-6-
TL;DR: Some commercial molecular sieves promote direct dimerization of free pyranose and furanose sugars stereoselectively into the corresponding α,α-disaccharides as discussed by the authors.
TL;DR: A family of [ 6-O-(1,2:3,4- di -O- isopropylidene-α-d -galactopyranosyl)methyl]tin species Ph n Sn(CH 2 OR) 4− n (1 n = 1−3 ), Ph n Me 3−n SnCh 2 I (n = 1-3) and Bu 3 SnCH2 OR (3) have been prepared from 1,2 : 3, 4-4-d-methyl compounds as mentioned in this paper.
TL;DR: In this article, a selection of 42 monosaccharides and related compounds were examined and in each case unique spectra were obtained for the differing compounds and their isomeric forms, allowing unambiguous identification.
TL;DR: In this paper, the assignment of the 1 H, 19 F, and 13 C NMR chemical shifts and coupling constants of 2-deoxy-2-fluoro- d -ribose, an important intermediate in the synthesis of antiviral nucleoside drugs, is reported and the NMR spectra are used to determine the proportions of the pyranose and furanose forms together with the anomeric ratios in acetone-d 6 solution.
TL;DR: The X-ray structure of a chicken egg white lysozyme (ChEWL) complex with a peptidoglycan-derived inhibitor suggests that interactions of Asn46 and Asp52 with the D-subsite N-acetylmuramic acid residue help to distort that pyranose ring into the reactive half-chair conformation and that a hydrogen bond is formed between Asn 46 and AsP52.
Abstract: The X-ray structure of a chicken egg white lysozyme (ChEWL) complex with a peptidoglycan-derived inhibitor suggests that interactions of Asn46 and Asp52 with the D-subsite N-acetylmuramic acid residue help to distort that pyranose ring into the reactive half-chair conformation and that a hydrogen bond is formed between Asn46 and Asp52 [Strynadka, N. C. J., & James, M. N. G. (1991) J. Mol. Biol. 220, 401-424]. These hypotheses were investigated through the D52A, N46A, and D52A/N46A mutants of ChEWL. The Michaelis constants of the D52A and D52A/N46A ChEWL complexes with Micrococcus luteus cells are 3- and 4-fold higher, respectively, than the wild-type KM; the corresponding kcat values are 25- and 50-fold lower, respectively, than the wild-type kcat. These results support the proposal of Strynadka and James. The velocities of reactions catalyzed by the N46A and D52A mutants are approximately equal to each other for all classes of substrate, suggesting that the respective roles of Asn46 and Asp52 in transition state stabilization do not vary. The mutation of either Asn46 or Asp52 to Ala apparently disrupts the interactions of the other (nonmutated) residue with the substrate, supporting the crystallographic evidence of a hydrogen-bond interaction between the two residues. The mutations do not change the values of the dissociation constants of complexes with (carboxymethyl)chitin complexes, suggesting that ground state complexes of ChEWL with chitin-derived substrates differ in conformation from complexes with bacterial peptidoglycans.
TL;DR: The first example of a crystalline urazole nucleoside has been synthesized from the reaction of D-deoxy-ribose with urazoles and characterized by X-ray crystallography as a single α-pyranoside diastereomer as mentioned in this paper.
Abstract: The first example of a crystalline urazole nucleoside has been synthesized from the reaction of D-deoxy-ribose with urazole and characterized by X-ray crystallography as a single α-pyranoside diastereomer [IUPAC name : 1-(2-deoxy-α-D-erythro-pentopyranosyl)-1(R),2(R),4-triazolidine-3,5-dione, C 7 H 11 N 3 O 5 ]. The pyranosyl group and H atom on the two pyramidal hydrazidic N atoms have an R,R-trans configuration, and the H atom on the trigonal imidic N atom is coplanar with the ring. Intermolecular hydrogen bonding is extensive and involves pyranose-pyranose, pyranose-urazole and urazole-urazole interactions. Each molecule is linked via eight hydrogen bonds to six surrounding molecules in which the urazole hydrazidic N(H) atom and imidic N atom are donors and carbonyl O atoms are acceptors, and the pyranose hydroxylic O atoms are donors as well as acceptors. The pyranose ring O atom does not participate in conventional hydrogen bonding but may be involved in a weak intermolecular C-H...O interaction.
TL;DR: The conformational behavior of a representative azaheterocycle/thiosugar hybrid: 6-S-(benzoxazol-2-yl)-6-deoxy-1,2:3,4-di-O-isopropylidene-6-thio-α-d-galactopyranose, 1, has been characterised by X-ray crystallography, molecular modelling and NMR studies.
TL;DR: The first example of a crystalline pyrazolidinedione nucleoside has been synthesized from the reaction of 2-deoxy-D-ribose with 4,4-dimethylpyrazolidine-3,5-dione and characterized by X-ray crystallography as a single α-pyranoside diastereomer.
Abstract: The first example of a crystalline pyrazolidinedione nucleoside has been synthesized from the reaction of 2-deoxy-D-ribose with 4,4-dimethylpyrazolidine-3,5- dione and characterized by X-ray crystallography as a single α-pyranoside diastereomer [IUPAC name: 1- (2-deoxy-α-D-erythro-pentopyranosyl) 1(R),2(R)-4,4-dimethylpyrazolidine-3,5-dione], C 10 H 16 N 2 O 5 . Although the pyrazolidinedione ring is essentially planar, the two hydrazidic N atoms are pyramidal and chiral, their respective pyranosyl and H-atom substituents being trans-R,R configured. The intermolecular hydrogen bonding involves pyranose-pyranose and pyranosepyrazolidinedione interactions. Each molecule is linked via six hydrogen bonds to four surrounding molecules in which the pyrazolidinedione hydrazidic N(H) atom is a donor and its adjacent carbonyl O atom is an acceptor, and the pyranose hydroxylic O atoms are donors as well as acceptors. The second carbonyl O atom has no hydrogen-bonding interactions with OH or NH, but exhibits a weak C-H...O intermolecular interaction with the pyranose ring. The pyranose ring O atom does not participate in hydrogen bonding. Substituting the OH groups with OD and the NH with ND resulted in no measurable changes in the structure (within error), including the hydrogen-bonding parameters.