Sequential Glycosylation Research Articles

Sequential One‐Pot Glycosylations Using 1‐Hydroxyl and 1‐Thiodonors.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Convergent Total Syntheses of Oligosaccharides by One-Pot Sequential Stereoselective Glycosylations

Abstract A convergent total synthesis of F1α antigen, a member of the tumor-associated O-linked mucin glycosyl amino acid, was tried by one-pot sequential glycosylation. Highly α-selective glycosylation of amino acid 7 with thioglycoside 6 was successfully carried out by combining trityl trifluoromethanesulfonate (TrOTf) and N-iodosuccimide (NIS) which gave glycosyl amino acid 21 in high yield (97%, α/β = 83⁄17). Next, the glycosylation of thioglycoside 4 with galactosyl phenyl carbonate 2 or fluoride 3 was tried by the promotion of trityl tetrakis(pentafluorophenyl)borate [TrB(C6F5)4] or trifluoromethanesulfonic acid (TfOH); protected F1α 25 was afforded in 80 or 89% overall yield, respectively, by the further addition of glycosyl amino acid 5 and NIS. The desired trisaccharide was obtained in high yield after removal of the protecting groups. Next, a convergent total synthesis of branched hepta-β-glucoside 30 having phytoalexin-elicitor activity was efficiently performed by way of two one-pot sequential glycosylation reactions: that is, trisaccharide 34 was synthesized in high yield by TfOH-catalyzed one-pot glycosylation using three given monosaccharides (31, 35, and 36) as shown in Scheme 12 and by subsequent selective deprotection of 6′-O-TBDPS group. The second one-pot glycosylation of trisaccharide 34 with three monosaccharides (31, 32, and 33d) also proceeded smoothly to afford heptaglucoside 43 stereoselectively in 48% total yield based on monosaccharide 32. Phytoalexin-elicitor active branched hepta-β-glucoside 30 was afforded by the sequential deprotection.

Highly α‐Stereoselective One‐Pot Sequential Glycosylation Using Glucosyl Thioformimidate Derivatives.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Sequential one-pot glycosylations using 1-hydroxyl and 1-thiodonors.

[reaction: see text] A novel sequential glycosylation procedure is described that combines the use of 1-hydroxyl and thiodonors. The Ph(2)SO/Tf(2)O-mediated dehydrative condensation of 1-hydroxyl donors with thioglycosides affords in good yield the thiodisaccharides, which in turn can be activated by the same activator system to furnish trisaccharides. The alpha-Gal epitope and a hyaluronan trisaccharide were efficiently assembled in a one-pot procedure.

Use of combinatorial genetic libraries to humanize N-linked glycosylation in the yeast Pichia pastoris.

The secretory pathway of Pichia pastoris was genetically re-engineered to perform sequential glycosylation reactions that mimic early processing of N-glycans in humans and other higher mammals. After eliminating nonhuman glycosylation by deleting the initiating alpha-1,6-mannosyltransferase gene from P. pastoris, several combinatorial genetic libraries were constructed to localize active alpha-1,2-mannosidase and human beta-1,2-N-acetylglucosaminyltransferase I (GnTI) in the secretory pathway. First, >32 N-terminal leader sequences of fungal type II membrane proteins were cloned to generate a leader library. Two additional libraries encoding catalytic domains of alpha-1,2-mannosidases and GnTI from mammals, insects, amphibians, worms, and fungi were cloned to generate catalytic domain libraries. In-frame fusions of the respective leader and catalytic domain libraries resulted in several hundred chimeric fusions of fungal targeting domains and catalytic domains. Although the majority of strains transformed with the mannosidase/leader library displayed only modest in vivo [i.e., low levels of mannose (Man)(5)-(GlcNAc)(2)] activity, we were able to isolate several yeast strains that produce almost homogeneous N-glycans of the (Man)(5)-(GlcNAc)(2) type. Transformation of these strains with a UDP-GlcNAc transporter and screening of a GnTI leader fusion library allowed for the isolation of strains that produce GlcNAc-(Man)(5)-(GlcNAc)(2) in high yield. Recombinant expression of a human reporter protein in these engineered strains led to the formation of a glycoprotein with GlcNAc-(Man)(5)-(GlcNAc)(2) as the primary N-glycan. Here we report a yeast able to synthesize hybrid glycans in high yield and open the door for engineering yeast to perform complex human-like glycosylation.

Highly α-Stereoselective One-pot Sequential Glycosylation Using Glucosyl Thioformimidate Derivatives

Abstract Several trisaccharides were prepared by efficient highly α-stereoselective one-pot sequential glycosylation using glucosyl p-trifluoromethylbenzylthio-p-trifluoromethylphenyl formimidates (abbreviated to: glucosyl thioformimidates) in the presence of a catalytic amount of TfOH. Factors that controlled the high α-stereoselectivity were determined by characteristic properties of thioformimidate groups contained both in glucosyl donor and acceptor.

Convergent and Convenient Total Synthesis of Phytoalexin‐Elicitor Active Heptasaccharide by One‐Pot Sequential Glycosylation.

Convergent and convenient total synthesis of branched hepta-β-glucoside 1 having phytoalexin-elicitor activity was efficiently accomplished by way of two one-pot sequential glycosylation reactions. Trisaccharide 8 was synthesized in high yield by TfOH-catalyzed one-pot glycosylation using three component monosaccharides and subsequent selective deprotection of a 6′-O-TBDPS group. The second one-pot glycosylation of trisaccharide 8 with the three monosaccharides smoothly proceeded to afford heptaglucoside 11 stereoselectively in 48% total yield based on monosaccharide 3. The targeted compound 1 was obtained in high yield after the removal of the protecting groups.

Convergent and Convenient Total Synthesis of Phytoalexin-Elicitor Active Heptasaccharide by One-Pot Sequential Glycosylation

Abstract Convergent and convenient total synthesis of branched hepta-β-glucoside 1 having phytoalexin-elicitor activity was efficiently accomplished by way of two one-pot sequential glycosylation reactions. Trisaccharide 8 was synthesized in high yield by TfOH-catalyzed one-pot glycosylation using three component monosaccharides and subsequent selective deprotection of a 6′-O-TBDPS group. The second one-pot glycosylation of trisaccharide 8 with the three monosaccharides smoothly proceeded to afford heptaglucoside 11 stereoselectively in 48% total yield based on monosaccharide 3. The targeted compound 1 was obtained in high yield after the removal of the protecting groups.

ChemInform Abstract: The First Synthesis of Tetraglucosyl Glucitol Having Phytoalexin‐Elicitor Activity in Rice Cells Based on a Sequential Glycosylation Strategy.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

One-pot synthesis of glucosamine oligosaccharides.

[reaction: see text] Tuning the reactivity of glycosyl donors derived from 2-amino-2-deoxy glucose by selective introduction of different N-protecting (NPhth and NHTroc) and anomeric leaving groups (ethylthio and phenylthio) enabled highly efficient oligosaccharide synthesis in a one-pot manner. One-pot sequential glycosylation of three and four units of 2-amino-2-deoxy glucose gave trisaccharides and tetrasaccharide in 50-81% yields.

The first synthesis of tetraglucosyl glucitol having phytoalexin-elicitor activity in rice cells based on a sequential glycosylation strategy

We describe a highly convergent approach for the synthesis of the tetraglucosyl glucitol 1 and its derivatives 4 , 5 and 6 which exhibit phytoalexin-elicitor activity in rice cells based on sequential glycosylation.

A Convergent Total Synthesis of the Mucin Related F1α Antigen by One-Pot Sequential Stereoselective Glycosylation

Abstract A convergent total synthesis of F1α antigen, a member of the tumor-associated O-linked mucin glycosyl amino acids, was accomplished by one-pot sequential glycosylation. In the first step, the corresponding disaccharide was formed from galactosyl phenylcarbonate 2 or fluoride 3 and thioglycoside 4 by the promotion of TrB(C6F5)4 or TfOH, and following glycosylation of glycosyl amino acid 5 by further addition of N-iodosuccinimide(NIS) afforded protected F1α in 80 or 89% overall yield, respectively. By the subsequent deprotection, F1α antigen was obtained in good yield.

The 2-Naphthylmethyl (NAP) Group in Carbohydrate Synthesis: First Total Synthesis of the GlyCAM-1 Oligosaccharide Structures

Total syntheses of the GlyCAM-1 (glycosylation-dependent cell adhesion molecule-1) oligosaccharide structures: {α-NeuAc-(2→3)-β-Gal-(1→4)-[α-Fuc-(1→3)]-β-(6-O-SO3Na)-GlcNAc-(1→6)}-[α-NeuAc-(2→3)-β-Gal-(1→3)]-α-GalNAc-OMe (1) and {α-NeuAc-(2→3)-β-Gal-(1→4)-[α-Fuc-(1→3)]-β-GlcNAc-(1→6)}-[α-NeuAc-(2→3)-β-Gal-(1→3)]-α-GalNAc-OMe (2) through a novel sialyl Lewisx tetrasaccharide donor are described. Employing sequential glycosylation strategy, the starting trisaccharide was regio- and stereoselectively constructed through coupling of a disaccharide imidate with the monosaccharide acceptor phenyl-6-O-naphthylmethyl-2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside with TMSOTf as a catalyst without affecting the SPh group. The novel sialyl Lewisx tetrasaccharide donor 3 was then obtained by α-L-fucosylation of trisaccharide acceptor with the 2,3,4-tri-O-benzyl-1-thio-β-L-fucoside donor. The structure of the novel sialyl Lewisx tetrasaccharide was established by a combination of 2D DQF-COSY and 2D ROESY experiments. Target oligosaccharides 1 and 2 were eventually constructed through heptasaccharide which was obtained by regioselective assembly of advanced sialyl Lewisx tetrasaccharide donor 3 and a sialylated trisaccharide acceptor in a predictable and controlled manner. Finally, target heptasaccharides 1 and 2 were fully characterized by 2D DQF-COSY, 2D ROESY, HSQC, HMBC experiments and FAB mass spectroscopy.

The 2-naphthylmethyl (NAP) group in carbohydrate synthesis: first total synthesis of the GlyCAM-1 oligosaccharide structures.

Total syntheses of the GlyCAM-1 (glycosylation-dependent cell adhesion molecule-1) oligosaccharide structures: [alpha-NeuAc-(2 --> 3)-beta-Gal-(1 --> 4)-[alpha-Fuc-(1 --> 3)]-beta-(6-O-SO3Na)-GlcNAc-(1 --> 6)]-[alpha-NeuAc-(2 --> 3)-beta-Gal-(1 --> 3)]-alpha-GalNAc-OMe (1) and [alpha-NeuAc-(2 --> 3)-beta-Gal-(1 --> 4)-[alpha-Fuc-(1 --> 3)]-beta-GlcNAc-(1 --> 6)]-[alpha-NeuAc-(2 3)-beta-Gal-(1 --> 3)]-alpha-GalNAc-OMe (2) through a novel sialyl LewisX tetrasaccharide donor are described. Employing sequential glycosylation strategy, the starting trisaccharide was regio- and stereoselectively constructed through coupling of a disaccharide imidate with the monosaccharide acceptor phenyl-6-O-naphthylmethyl-2-deoxy-2-phthalimido-1-thio-beta-D-glucopyranoside with TMSOTf as a catalyst without affecting the SPh group. The novel sialyl Lewisx tetrasaccharide donor 3 was then obtained by alpha-L-fucosylation of trisaccharide acceptor with the 2,3,4-tri-O-benzyl-1-thio-beta-L-fucoside donor. The structure of the novel sialyl Lewisx tetrasaccharide was established by a combination of 2D DQF-COSY and 2D ROESY experiments. Target oligosaccharides 1 and 2 were eventually constructed through heptasaccharide which was obtained by regioselective assembly of advanced sialyl Lewisx tetrasaccharide donor 3 and a sialylated trisaccharide acceptor in a predictable and controlled manner. Finally, target heptasaccharides 1 and 2 were fully characterized by 2D DQF-COSY, 2D ROESY, HSQC, HMBC experiments and FAB mass spectroscopy.

Synthesis of a group of diosgenyl saponins by a one-pot sequential glycosylation

A group of natural diosgenyl saponins was synthesized in a highly efficient manner employing the ‘one-pot sequential glycosylation’ protocol with the combined use of glycosyl trichloroacetimidates and thioglycosides.

ChemInform Abstract: One‐Pot Sequential Glycosylation: A New Method for the Synthesis of Branched Oligosaccharides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

One-pot sequential glycosylation:A new method for the synthesis of branched oligosaccharides

One-pot glycosylations of glycosyl bromides and phenylthio glycosides with various dihydroxyl glycosyl acceptors have been examined to provide the corresponding branched trisaccharides.

Intracellular Transport and Maturation Pathway of Human Herpesvirus 6

A peculiar characteristic of cells infected with human herpesvirus 6 (HHV6) is the absence of viral glycoproteins on the plasma membrane, which may reflect an atypical intracellular transport of the virions and/or the viral glycoproteins, different from that of the other members of the herpesvirus family. To investigate the maturation pathway of HHV-6 in the human T lymphoid cell line HSB-2, we used lectin cytochemistry and immunogold labeling combined with several electron microscopical techniques, such as ultrathin frozen sections, postembedding, and fracture-label. Immunolabeling with anti-gp116 and anti-gp82-gp105 monoclonal antibodies revealed that the viral glycoproteins are undetectable on nuclear membranes and that at the inner nuclear membrane nucleocapsids acquire a primary envelope lacking viral glycoproteins. After de-envelopment, cytoplasmic nucleocapsids acquire a thick tegument and a secondary envelope with viral glycoproteins at the level of neo-formed annulate lamellae or at thecis-side of the Golgi complex. Cytochemical labeling using helix pomatia lectin revealed that the newly acquired secondary viral envelopes contain intermediate forms of glycocomponents, suggesting a sequential glycosylation of the virions during their transit through the Golgi area before their final release into the extracellular space. Immunogold labeling also showed that the viral glycoproteins, which are not involved in the budding process, reach and accumulate in the endosomal/lysosomal compartment. Pulse-chase analysis indicated degradation of the gp116, consistent with its endosomal localization and with the absence of viral glycoproteins on the cell surface of the infected cells.

One-pot sequential glycosylation: A new method for the synthesis of oligosaccharides

Sequential one-pot glycosylations among various glycosidic donors (glycosyl bromide, glycosyl trichloroimidate, glycosyl fluoride), a β-thiophenyl glycoside derivative and a α-methyl glycoside derivative have been attempted to give the corresponding trisaccharides.

A candidate mammalian glycoinositol phospholipid precursor containing three phosphoethanolamines

The glycoinositol phospholipid (GPI) anchors of mammalian proteins contain linear ethanolamine (EthN)-P-6ManManManGlcN glycan sequences that bear additional EthN-P substituents and in some cases include a fourth Man and a GalNAc or sialic acid-GalGalNAc. Precursors of these anchoring structures are preassembled in the endoplasmic reticulum by sequential glycosylation of inositol phospholipid. In previous studies (Hirose, S., Prince, G. M, Sevlever, D., Ravi, L., Rosenberry, T. L., Ueda, E., and Medof, M. E. (1992) J. Biol. Chem. 267, 16968-16974), a series of putative intermediates of this assembly process were isolated from human HeLa cells and murine lymphomas, and several of the more polar products were found to contain a second EthN-P attached to the Man residue (Man 1) proximal to GlcN. In this study, the most polar HeLa cell GPI species was purified by normal phase HeLa cell GPI species was purified by normal phase Iatrobead high performance liquid chromatography, and its glycan was characterized. Dionex anion exchange chromatographic analyses of fragments produced by nitrous acid deamination, hydrofluoric acid dephosphorylation, and trifluoroacetic acid hydrolysis in conjunction with biosynthetic labeling studies indicated a structure containing a third EthN-P substituent linked to the 6-position of Man 2. The polar GPI product exhibited a ManManManGlcN core lacking additional Man or GalNAc. The implications of the identification of this triply phosphoethanolamine-substituted species to mammalian GPI anchor biosynthesis are discussed.