Trisaccharide Derivative Research Articles

BF3 ⋅ CH3CN Promotes a Formation of Aryl α‐O‐Glycosides from Pyranoses: A Facile Approach to Oligosaccharide EPS‐G7

AbstractA BF3 ⋅ CH3CN‐promoted synthesis of aryl α‐O‐glycosides from readily available glycosyl donors was developed. This reaction could proceed well on a gram‐scale under mild condition with α/β ratio up to 95 : 5. Moreover, a variety of the glycosyl donors including acetylated/benzoylated pyranoses, di‐ and trisaccharide derivatives as well as glycosyl acceptors from substituted phenols, sterically hindered aliphatic alcohols and carboxylic acid, were well tolerant. Importantly, the potential of this strategy was highlighted with a successful gram‐scale synthesis of oligosaccharide EPS‐G7, which is a commercial detection reagent for quantitative determination of α‐amylase.

Synthesis of β-1,3-glucan mimics by β-1,3-glucan trisaccharyl monomer polymerization

β-1,3-Glucans are important as immunostimulating agents in living organisms. The multivalent binding of β-1,3-glucans to dectin-1, a cell surface receptor, activates immunological defenses. To study artificial immunostimulating agents, glycopolymers carrying β-1,3-glucan trisaccharides as artificial ligands were synthesized. The β-1,3-glucan trisaccharide, defined as an active unit of β-1,3-glucan, was constructed from D-glucose by glycosylation. A norbornene group was introduced as a polymerizable group into the trisaccharide derivative at the aglycone. The prepared endo/exo norbornene stereoisomers of the monomers were separated by silica gel chromatography and identified by NMR spectroscopy and mass spectrometry. The synthesized glycosyl monomers were polymerized and copolymerized with norbornene using 2nd generation Hoveyda-Grubbs catalyst, deprotected, and purified by gel filtration to prepare water-soluble glycopolymers of varied compositions and high molecular weights. These polymers will have the potential for multivalent binding to dectin-1 to activate immune response and facilitate studies to understand the binding mechanisms of β-1,3-glucans with dectin-1.

Regio/Stereoselective Glycosylation of Diol and Polyol Acceptors in Efficient Synthesis of Neu5Ac-α-2,3-LacNPhth Trisaccharide.

A concise approach to a Neu5Ac-α-2,3-LacNPhth trisaccharide derivative was developed. First, the regio/stereoselective glycosylation between glycoside donors and glucoNPhth diol acceptors was investigated. It was found that the regioselectivity depends not only on the steric hindrance of the C2-NPhth group and the C6-OH protecting group of the glucosamine acceptors, but also on the leaving group and protecting group of the glycoside donors. Under optimized conditions, LacNPhth derivatives were synthesized in up to 92 % yield through a regio/stereoselective glycosylation between peracetylated-α-galactopyranosyl trichloroacetimidate and p-methoxyphenyl 6-O-tert-butyldiphenylsilyl-2-deoxy-2-phthalimido-β-d-glucopyranoside, avoiding the formation of glycosylated orthoesters and anomeric aglycon transfer. Then, the LacNPhth derivative was deacylated and then protected on the primary position by TBDPS to form a LacNPhth polyol acceptor. Finally, the Neu5Ac-α-2,3-LacNPhth derivative was synthesized in 48 % yield through the regio/stereoselective glycosylation between the LacNPhth polyol acceptor and a sialyl phosphite donor. Starting from d-glucosamine hydrochloride, the target Neu5Ac-α-2,3-LacNPhth derivative was synthesized in a total yield of 18.5 % over only 10 steps.

Sequential Functionalizations of Carbohydrates Enabled by Boronic Esters as Switchable Protective/Activating Groups.

Processes for site-selective, sequential functionalizations of carbohydrate derivatives are described. In these processes, a tricoordinate boronic ester initially serves as a protective group for a sugar-derived 1,2- or 1,3-diol motif, permitting functionalization of free OH groups. In a second step, addition of a Lewis base generates a tetracoordinate adduct, which serves as an activating group, enabling functionalization of one of the boron-bound oxygen atoms by a second electrophile. By combining an initial acylation, alkylation, or glycosylation step with an amine-mediated glycosylation of the boronic ester, a variety of selectively protected di- and trisaccharide derivatives can be accessed in an operationally simple fashion without purification of intermediates. This Lewis base-triggered switching of behavior from "latent" to "active" nucleophile is a unique feature of boronic esters relative to other protective groups for diol moieties in carbohydrate chemistry.

Regioselective 5-O-Opening of Conformationally Locked 3,5-O-Di-tert-butylsilylene-d-galactofuranosides. Synthesis of (1→5)-β-d-Galactofuranosyl Derivatives.

The use of thiogalactofuranoside as donors for the construction of internal Galf containing oligosaccharide is limited, probably due to the difficulty to functionalize thiogalactofuranoside derivatives showing O-2, O-3, and O-5 with similar reactivity. An efficient method for complete regioselective 5-O-opening of conformationally restricted 3,5-O-di-tert-butylsilylene-d-galactofuranoside derivatives was developed. The use of a solution nBu4NF (1.1 equiv) in CH2Cl2 on 6 gave the 5-OH free derivative 10 as the only product (90%). 3-O-Di-tert-butylhydroxysilyl derivative 10 was stable upon purification and glycosylation reaction. Preactivation of conformationally restricted thioglycoside 6 employing p-NO2-benzensulfenyl chloride/AgOTf followed by condensation over the 5-OH thioglycoside acceptor 10 gave the corresponding disaccharide 12 without autocondensation byproduct. Regioselective 5-O-deprotection was also successfully performed over the (1→5)-β-d-galactofuranosyl di- and trisaccharide derivatives 12 and 13. This methodology allowed the differentiation between the secondary hydroxyl groups OH-3 and OH-5 of 1,2-cis or 1,2-trans d-galactofuranoside derivatives, and it still constitutes an innovative approach to access oligosaccharides of pharmacological importance.

N-Acetyl glycals are tight-binding and environmentally insensitive inhibitors of hexosaminidases

Mono-, di- and trisaccharide derivatives of 1,2-unsaturated N-acetyl-d-glucal have been synthesized and shown to function as tight-binding inhibitors/slow substrates of representative hexosaminidases. Turnover is slow and not observed in the thioamide analogue, allowing determination of the 3-dimensional structure of the complex. Inhibition is insensitive to pH and to mutation of key catalytic residues, consistent with the uncharged character of the inhibitor. These properties could render this inhibitor class less prone to development of resistance.

ChemInform Abstract: Chemistry and Anticarcinogenic Mechanisms of Glycoalkaloids Produced by Eggplants, Potatoes, and Tomatoes

AbstractReview: 141 refs.

Chemistry and anticarcinogenic mechanisms of glycoalkaloids produced by eggplants, potatoes, and tomatoes.

Inhibition of cancer can occur via apoptosis, a genetically directed process of cell self-destruction that involves numerous biomarkers and signaling pathways. Glycoalkaloids are nitrogen-containing secondary plant metabolites found in numerous Solanaceous plants including eggplants, potatoes, and tomatoes. Exposure of cancer cells to glycoalkaloids produced by eggplants (α-solamargine and α-solasonine), potatoes (α-chaconine and α-solanine), and tomatoes (α-tomatine) or their hydrolysis products (mono-, di-, and trisaccharide derivatives and the aglycones solasodine, solanidine, and tomatidine) inhibits the growth of the cells in culture (in vitro) as well as tumor growth in vivo. This overview comprehensively surveys and consolidates worldwide efforts to define the following aspects of these natural compounds: (a) their prevalence in the three foods; (b) their chemistry and structure-activity relationships; (c) the reported factors (biomarkers, signaling pathways) associated with apoptosis of bone, breast, cervical, colon, gastric, glioblastoma, leukemia, liver, lung, lymphoma, melanoma, pancreas, prostate, and squamous cell carcinoma cell lines in vitro and the in vivo inhibition of tumor formation and growth in fish and mice and in human skin cancers; and (d) future research needs. The described results may make it possible to better relate the structures of the active compounds to their health-promoting function, individually, in combination, and in food, and allow the consumer to select glycoalkaloid-containing food with the optimal content of nontoxic beneficial compounds. The described findings are expected to be a valuable record and resource for further investigation of the health benefits of food-related natural compounds.

Neutral and acidic products derived from hydroxyl radical-induced oxidation of arabinotriose assessed by electrospray ionisation mass spectrometry

The oxidation of α-(1 → 5)-L-arabinotriose (Ara3), an oligosaccharide structurally related to side chains of coffee arabinogalactans, was studied in reaction with hydroxyl radicals generated under conditions of Fenton reaction (Fe(2+)/H2O2). The acidic and neutral oxidation products were separated by ligand exchange/size-exclusion chromatography, subsequently identified by electrospray ionisation mass spectrometry (ESI-MS) and structurally characterised by tandem MS (ESI-MS/MS). In acidic fraction were identified several oxidation products containing an acidic residue at the corresponding reducing end of Ara3, namely arabinonic acid, and erythronic, glyceric and glycolic acids formed by oxidative scission of the furanose ring. In neutral fractions were identified derivatives containing keto, hydroxy and hydroperoxy moieties, as well as derivatives resulting from the ring scission at the reducing end of Ara3. In both acidic and neutral fractions, beyond the trisaccharide derivatives, the corresponding di- and monosaccharide derivatives were identified indicating the occurrence of oxidative depolymerisation. The structural characterisation of these oxidation products by ESI-MS/MS allowed the differentiation of isobaric and isomeric species of acidic and neutral character. The species identified in this study may help in detection of roasting products associated with the free radical-mediated oxidation of coffee arabinogalactans.

The Crystal Structure of Shiga Toxin Type 2 with Bound Disaccharide Guides the Design of a Heterobifunctional Toxin Inhibitor

Shiga toxin type 2 (Stx2a) is clinically most closely associated with enterohemorrhagic E. coli O157:H7-mediated hemorrhagic colitis that sometimes progresses to hemolytic-uremic syndrome. The ability to express the toxin has been acquired by other Escherichia coli strains, and outbreaks of food poisoning have caused significant mortality rates as, for example, in the 2011 outbreak in northern Germany. Stx2a, an AB5 toxin, gains entry into human cells via the glycosphingolipid receptor Gb3. We have determined the first crystal structure of a disaccharide analog of Gb3 bound to the B5 pentamer of Stx2a holotoxin. In this Gb3 analog,-GalNAc replaces the terminal-Gal residue. This co-crystal structure confirms previous inferences that two of the primary binding sites identified in theB5 pentamer of Stx1 are also functional in Stx2a. This knowledge provides a rationale for the synthesis and evaluation of heterobifunctional antagonists for E. coli toxins that target Stx2a. Incorporation of GalNAc Gb3 trisaccharide in a heterobifunctional ligand with an attached pyruvate acetal, a ligand for human amyloid P component, and conjugation to poly[acrylamide-co-(3-azidopropylmethacrylamide)] produced a polymer that neutralized Stx2a in a mouse model of Shigatoxemia.

First total synthesis of natural pulsatilla saponin D via highly stereospecific glycosylation

The first total synthesis of pulsatilla saponin D, a potent anti-lung cancer natural product was accomplished in eight steps from l-arabinopyranoside in high overall yield via a highly stereospecific glycosylation featuring an oxocarbenium mechanism between the trisaccharide derivative and aglycone as the key step.

Synthesis of a new glycosphingolipid from the marine ascidian Microcosmus sulcatus using a one-pot glycosylation strategy

A novel neutral glycosphingolipid found in Microcosmus sulcatus containing a β-d-Galp(1→4)[α-d-Fucp-(1→3)]β-d-Glcp-(1→)Cer motif was synthesized. Trisaccharide derivatives were synthesized using trimethylsilyltrifluoromethanesulfanate (TMSOTf) and N-iodosuccimide (NIS)/trifluoromethane sulfonic acid (TfOH) as the promoters. Synthesis was achieved with an efficient one-pot glycosylation strategy. This is the first report of a one-pot glycosylation strategy using the procedure of Boons et al. for the synthesis of a natural product. Coupling of trisaccharide derivative 19 and ceramide derivative 20 by TMSOTf afforded the glycosphingolipid derivative 21. The fully protected glycoside was deprotected to give the target glycosphingolipid 2.

ChemInform Abstract: Synthesis of Novel Carbohydrate Mimetics via 1,2‐Oxazines

AbstractReview: 45 refs.

Synthesis of novel carbohydrate mimetics via 1,2-oxazines

The combination of lithiated alkoxyallenes with carbohydrate-derived nitrones constitutes a flexible entry to highly functionalized enantiopure 1,2-oxazine derivatives. They can be used as precursors for acyclic and cyclic carbohydrate-like products such as amino sugar alcohols, azetidine and pyrrolidine derivatives. The Lewis acid-promoted rearrangement of 1,3-dioxolanyl-substituted 1,2-oxazines to bicyclic compounds allows an efficient route to novel amino pyran and oxepane derivatives. After subsequent transformations, new carbohydrate mimetics or “real” carbohydrates were obtained in good yield and often in a stereodivergent fashion. These compounds have already been employed for the preparation of unusual di- and trisaccharide derivatives. Several of the products prepared showed interesting biological activities, e.g., as L- and P-selectin inhibitors with IC50 values in the subnanomolar range.

Synthesis and evaluation of a radioiodinated trisaccharide derivative as a synthetic substrate for a sensitive N-acetylglucosaminyltransferase V radioassay

N-acetylglucosaminyltransferase V (GnT-V) is one of the most relevant glycosyltransferases to tumor invasion and metastasis. Based on previous findings of molecular recognition between GnT-V and synthetic substrates, we designed and synthesized a p-iodophenyl-derivatized trisaccharide, 2-(4-iodophenyl)ethyl 6-O-[2-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-α-d-mannopyranosyl]-β-d-glucopyranoside (IPGMG, 1) and its radiolabeled form, [125I]IPGMG ([125I]1), for use in assays of GnT-V activity in vitro. The tributyltin derivative, 2-[4-(n-tributylstannyl)phenyl]ethyl 6-O-[2-O-(3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-β-d-glucopyranosyl)-3,4,6-tri-O-acetyl-α-d-mannopyranosyl]-2,3,4-tri-O-acetyl-β-d-glucopyranoside (21), was synthesized as a precursor for the preparation of [125I]1. The iododestannylation of 21 using hydrogen peroxide as an oxidant followed by deacetylation yielded [125I]1. When [125I]1 was incubated in GnT-V-expressing cells with a UDP-GlcNAc donor, the production of β1–6GlcNAc-bearing IPGMG (IPGGMG, 2) was confirmed by radio-HPLC. In kinetic analysis, 1 was found to be a good substrate with a Km of 23.7μM and a Vmax of 159pmol/h. μg protein. [125I]1 would therefore be a useful synthetic substrate for the quantitative determination of GnT-V activity.

Multi‐stage mass spectrometric information obtained by deconvolution of energy‐resolved spectra acquired by triple‐quadrupole mass spectrometry

Triple-quadrupole mass spectrometry (TQ-MS) provides the capability to carry out collision-induced dissociation (CID) and it offers advantages in quantification when connected with high-performance liquid chromatography through an electrospray ionization interface. However, although TQ-MS provides information on partial structures through the analysis of product ions obtained by CID experiments, the method only provides single-stage CID experiments, which limits the detailed structural information that can be obtained. Herein, a method of overcoming this limitation of TQ-MS is described. A spectrum obtained by energy-resolved mass spectrometry (ERMS) was used to deconvolute the fragmentation process, with a Galili-antigenic trisaccharide derivative being used as an example. A replot of the ERMS data showing the ratios of the product ions to the precursor ion resulted in a descriptive graph. Analysis of the sum of the ratios of individual product ions to the precursor ion at specific CID energies revealed that the members of a series of product ions were related to each other. The obtained relationships and the m/z values of the product ions provided information on the fragmentation process taking place during the dissociation, indicating that the ERMS spectrum obtained by TQ-MS contained equivalent information to that obtainable by multi-stage MS/MS (MS(n); n≥2). This method may allow users of triple-quadrupole mass spectrometers to obtain MS(n)-type information by performing a single ERMS experiment, which is even advantageous over quadrupole ion trap (QIT)-MS/MS because CID experiments on individual first-generation product ions are not required.

A new trisaccharide derivative from Prenanthes purpurea

A methanolic extract of Prenanthes purpurea L. leaves yielded 1,6??-di-O-cinnamoyl-?-D-glucopyranosyl-(1?3)-O-?-Lrhamnopyranosyl-( 1?6)-O-?-D-glucopyranoside. The NMR and physical data of this new natural compound are reported.

Alternative Synthesis of Radioiodinated Trisaccharide Derivatives, 2-(4-125Iodophenyl)ethyl 2-Acetamido-2-deoxy-β-D-glucopyranosyl-(1→2)-α-D-mannopyranosyl-(1→6)-β-D-glucopyranoside, and Preparation of Its Analogs Having Different Lengths of Alkyl Chains Instead of Ethyl Group: Acceptor Substrates of N-Acetylglucosaminyltransferase V for in vivo Imaging

Alternative Synthesis of Radioiodinated Trisaccharide Derivatives, 2-(4-125Iodophenyl)ethyl 2-Acetamido-2-deoxy-β-D-glucopyranosyl-(1→2)-α-D-mannopyranosyl-(1→6)-β-D-glucopyranoside, and Preparation of Its Analogs Having Different Lengths of Alkyl Chains Instead of Ethyl Group: Acceptor Substrates of N-Acetylglucosaminyltransferase V for in vivo Imaging

Syntheses of novel azasugar-containing mimics of heparan sulfate fragments as potential heparanase inhibitors

A series of eight novel, highly modified mono-, di- and trisaccharide derivatives, each containing an iminoalditol moiety, has been synthesized in the quest for potential heparanase inhibitors.

Separation and structure analysis of trisaccharide isomers produced from lactose by Lactobacillus bulgaricus L3 β-galactosidase

Using lactose as the substrate, galacto-oligosaccharides containing β- d-galactose residues were synthesised with β-galactosidase from Lactobacillus bulgaricus L3. The reaction mixture was fermented by yeast cells to consume the monosaccharides and disaccharides, and then it was fully acetylated in the presence of acetic anhydride under I 2 catalysis. Column chromatography of the resulting products, using ethyl acetate: petroleum ether as the eluent, generated two isomers of trisaccharide derivatives ( I and II) in gram scale for the first time. Their structure characteristics were investigated by ESI-MS and NMR spectra. They were identified as (2,3,4,6-tetra- O-acetyl- d-galactopyranosyl)-β-(1 → 6)-(2,3,4-tri- O-acetyl- d-galactopyranosyl)-β-(1 → 4)-1,2,3,6-tetra- O-acetyl-α- d-glucopyranose ( I) and (2,3,4,6-tetra- O-acetyl- d-galactopyranosyl)-β-(1 → 3)-(2,4,6-tri- O-acetyl- d-galactopyranosyl)-β-(1 → 4)-1,2,3,6-tetra- O-acetyl-α- d-glucopyranose ( II), respectively. ESI-MS analysis of both deacetylated products of the two trisaccharide derivatives I and II revealed molecular ion peaks of free trisaccharides, which were structurally identified as Gal-β-(1 → 6)-Gal-β-(1 → 4)-Glc and Gal-β-(1 → 3)-Gal-β-(1 → 4)-Glc, respectively.