Trisaccharide Donor Research Articles

Direct Synthesis of 2,6‐Dideoxy‐β‐glycosides and β‐Rhamnosides with a Stereodirecting 2‐(Diphenylphosphinoyl)acetyl Group

AbstractAnomeric stereocontrol is usually one of the major issues in the synthesis of complex carbohydrates, particularly those involving β‐configured 2,6‐dideoxyglycoside and d/l‐rhamnoside moieties. Herein, we report that 2‐(diphenylphosphinoyl)acetyl is highly effective as a remote stereodirecting group in the direct synthesis of these challenging β‐glycosides under mild conditions. A deoxy‐trisaccharide as a mimic of the sugar chain of landomycin E was prepared stereospecifically in high yield. The synthetic potential was also highlighted in the synthesis of Citrobacter freundii O‐antigens composed of a [→4)‐α‐d‐Manp‐(1→3)‐β‐d‐Rhap(1→4)‐β‐d‐Rhap‐(1→] repeating unit, wherein the convergent assembly up to a nonasaccharide was realized with a strongly β‐directing trisaccharide donor. Variable‐temperature NMR studies indicate the presence of intermolecular H‐bonding between the donor and the bulky acceptor as direct spectral evidence in support of the concept of hydrogen‐bond‐mediated aglycone delivery.

A Modular Chemoenzymatic Synthesis of Disialosyl Globopentaosylceramide (DSGb5Cer) Glycan.

The total synthesis of the oligosaccharide moiety of disialosyl globopentaosylceramide (DSGb5 Cer), a dominant ganglioside isolated from malignant renal cell carcinoma tissues, is reported. The synthetic strategy relies on a chemical α(2,6)-sialylation at the internal GalNAc unit of a Gb5 pentasaccharide backbone that furnishes a Neu5Acα(2,6)GalNAc-linked hexasaccharide, suitable for an enzymatic α(2,3)-sialylation of the terminal Gal residue to construct a heptasaccharide glycan. Convergent access to this key α(2,6)-sialylated hexasaccharide was also achieved through a [3+3] glycosylation building upon a Galβ(1,3)[Neu5Acα(2,6)]GalNAc-based trisaccharide donor and a Gb3 acceptor. The synthetic DSGb5 glycan bearing a 6-azidohexyl aglycon at the reducing end could undergo further regioselective functionalization. This approach represents a viable chemoenzymatic method for accessing complex ganglioside glycans and should be useful for the synthesis and biological investigation of DSGb5 derivatives.

One-Pot Synthesis of the Repeating Unit of Type VII Group B Streptococcus Polysaccharide and the Dimer.

The first synthesis of the hexasaccharide repeating unit of type VII group B Streptococcus capsular polysaccharide was achieved by a one-pot glycosylation strategy. The dimer of this repeating unit was also synthesized by one-pot glycosylation to achieve the backbone hexasaccharide first followed by one-pot dual glycosylations with the side-chain trisaccharide donor. All glycosylation reactions gave excellent stereoselectivity, which took advantage of a new stereospecific α-glucosylation method and the neighboring group participation effect for 1,2- trans glycosylations.

First Total Synthesis of Trehalose-Containing Branched Oligosaccharide OSE-1 of Mycobacterium gordonae (Strain 990).

The first total synthesis of the branched oligosaccharide OSE-1 of Mycobacterium gordonae (strain 990) is reported. An intramolecular aglycon delivery approach was used for constructing the desymmetrized 1,1'-α,α-linked trehalose moiety. A [3+2] glycosylation of the trisaccharide donor and trehalose acceptor furnished the right hand side pentasaccharide. Regioselective O3 glycosylation of L-rhamnosyl 2,3-diol allowed expedient synthesis of the left hand side tetrasaccharide. The nonasaccharide was assembled in a highly convergent fashion through a [4+5] glycosylation.

Synthesis of unsymmetrical 3,6-branched Man5 oligosaccharide: a comparison between one-pot sequential glycosylation and stepwise synthesis

An expeditious three-component, one-pot sequential glycosylation protocol has been developed for the preparation of 3,6-branched unsymmetrical mannopentaose (Man5), employing a mannose trisaccharide donor, a mannose monosaccharide donor and a mannose monosaccharide acceptor. The high efficiency of this one-pot procedure was demonstrated by comparison study with a stepwise synthesis using the same three building blocks.

Synthesis of Biantennary Complex-Type Nonasaccharyl Asn Building Blocks for Solid-Phase Glycopeptide Synthesis

The biantennary complex-type N-glycans bearing LacNAc and LacdiNAc as the nonreducing end motif were synthesized in a protected form suitable to use in the Fmoc solid-phase peptide synthesis studies. Two approaches for the nonasaccharide synthesis were examined by taking advantage of the highly β-selective glycosylation with GlcNTCA (N-phenyl)trifluoroacetimidate. An earlier approach, which involved the reaction of the trisaccharide donor (Gal-GlcNTCA-Man) and trisaccharide acceptor (Man-GlcNPhth(2)-N(3)), produced a mixture of nonasaccharide isomers. On the other hand, mannosylation of the trisaccharide acceptor (Man-GlcNPhth(2)-N(3)) stereoselectively afforded the known pentasaccharide (Man(3)-GlcNPhth(2)-N(3)), which was reacted with the disaccharyl glycosyl donor (Gal-GlcNTCA or GalNTCA-GlcNTCA) to produce the desired nonasaccharide as a single stereoisomer. Selective dephthaloylation followed by N-acetylation furnished the GlcNAc(2) functionality. The resulting nonasaccharyl azides were condensed with Fmoc-Asp(OPfp)-OBu(t) or Fmoc-Asp(OPfp)-OPac in the presence of Ph(CH(3))(2)P and HOOBt. Finally, the Zn reduction and cleavage of the tert-butyl ester or Zn reduction alone produced the targeted nonasaccharyl Asn building blocks.

Stereoselective Synthesis of the Hexasaccharide Repeating Unit of the Cell Wall Polysaccharide from Kineosporia aurantiaca VKM Ac-720T Employing the Direct Glycosylation with Anomeric Hydroxy Sugars Involving Glycosyl Phthalate Intermediates

Synthesis of a suitably protected form of the hexasaccharide repeating unit of the cell wall polymer from Kineosporia aurantiaca VKM Ac-720 T has been achieved by the stereoselective direct glycosylation of a trisaccharide acceptor with a trisaccharide donor having an anomeric hydroxy group involving a glycosyl phthalate intermediate. Both the trisaccharide acceptor and the trisaccharide donor were obtained from a common trisaccharide, of which two β-mannopyranosyl linkages were constructed stereoselectively by employing the direct glycosylation method with the anomeric hydroxy sugar involving a glycosyl phthalate intermediate and the 2′-carboxybenzyl glycoside method, respectively.

Efficient Synthesis of an Allose-Containing Analogue of the Phytoalexin-Elicitor Glucohexaose and Its Dodecyl Glycoside

An allose-containing analogue 2 of thephytoalexin elicitor β-(1→3)-branched β-(1→6)-linkedglucohexatose and its dodecyl glycoside 3 hasbeen regio- and stereospecifically synthesized. As a typical exampleof the method, the synthesis of 2 was achieved viacoupling of the trisaccharide donor 2,3,4,6-tetra- O-benzoyl-β- D-glucopyranosyl-(1→3)-[2,3,4,6-tetra- O-benzoyl-β- D-glucopyranosyl-(1→6)]-1,2- O-isopropylidene-α- D-allopyranosyl trichloroacetimidate ( 9) with a trisaccharide acceptor. The donorwas prepared easily from 1,2:5,6-di- O-isopropylidene-α- D-allofuranose ( 5)and 2,3,4,6-tetra- O-benzoyl-α- D-glucopyranosyl trichloroacetimidate ( 4) in a regio- and stereoselective manner.

Synthesis of a heptasaccharide fragment of the mannan from Candida guilliermondii cell wall and its conjugate with BSA

The 3-aminopropyl glycoside of a heptasaccharide fragment of the cell wall mannan from Candida guilliermondii 18, which corresponds to the antigenic Factor 9, has been synthesized by a convergent approach based on glycosylation of a tetrasaccharide acceptor with a trisaccharide donor as the key step to give a protected heptasaccharide 17. Subsequent two-step deprotection of 17 afforded the heptamannoside 18, which was then conjugated with BSA using the squarate procedure.

Synthesis of galactose-containing analogues of (1→6)-branched (1→3)-glucohexaose and its lauryl glycoside

Coupling of the trisaccharide acceptor either 2,4,6-tri- O-acetyl-β- D-glucopyranosyl-(1→3)-[2,3,4,6-tetra- O-benzoyl-β- D-glucopyranosyl-(1→6)]-5- O-acetyl-1,2- O-isopropylidene-α- D-glucofuranose ( 13) or lauryl 2,4,6-tri- O-acetyl-β- D-glucopyranosyl-(1→3)-[2,3,4,6-tetra- O-benzoyl-β- D-glucopyranosyl-(1→6)]-2,5-di- O-acetyl-α- D-glucopyranoside ( 15) with the trisaccharide donor 2,3,4,6-tetra- O-benzoyl-β- D-glucopyranosyl-(1→3)-[2,3,4,6-tetra- O-benzoyl-β- D-glucopyranosyl-(1→6)]-2,4-di- O-acetyl-α- D-galactopyranosyl trichloroacetimidate ( 12) gave α-linked hexasaccharides 14 and 16, respectively, while coupling of either 13 or 15 with trisaccharide donor 2,3,4,6-tetra- O-benzoyl-β- D-galactopyranosyl-(1→3)-[2,3,4,6-tetra- O-benzoyl-β- D-galactopyranosyl-(1→6)]-2,4-di- O-acetyl-α- D-galactopyranosyl trichloroacetimidate 17 did not afford any hexasaccarides. The analogues of the immunomodulator β- D-Glc p-(1→3)-[β- D-Glc p-(1→6)]-α- D-Glc p-(1→3)-β- D-Glc p-β-(1→3)-[β- D-Glc p-(1→6)]-β- D-Glc p ( 1) was obtained by deprotection of 14 and 16.

Synthesis of an α-linked dimer of the trisaccharide repeating unit of the exopolysaccharide produced by Pediococcus damnosus 2.6

A hexasaccharide, β- d-Glc p-(1→3)-[β- d-Glc p-(1→2)]-α- d-Glc p-(1→3)-β- d-Glc p-(1→3)-[β- d-Glc p-(1→2)]- d-Glc p, the α-linked dimer of the trisaccharide repeating unit of the exopolysaccharide produced by Pediococcus damnosus 2.6, was synthesized as its methyl glycoside. Condensation of fully benzoylated α- d-glucopyranosyl trichloroacetimidate ( 1) with isopropyl 4,6- O-benzylidene-1-thio-β- d-glucopyranoside ( 2) selectively furnished (1→3)-linked disaccharide 3, and subsequent 2-O-acetylation, desulfation, and trichloroacetimidate formation afforded the disaccharide donor 6. Meanwhile, selective 3-O-coupling of methyl 4,6- O-benzylidene-α- d-glucopyranoside ( 8) with 3- O-allyl-2,4,6-tri- O-benzoyl-α- d-glucopyranosyl trichloroacetimidate ( 7), followed by coupling with 1 gave the trisaccharide 10. Removal of the benzylidene group of 10, benzoylation, and deallylation produced the trisaccharide acceptor 12. Condensation of 12 with 6 yielded a pentasaccharide mixture 13 with β and α isomers in a ratio of 2:1. Removal of the benzylidene group of 13, followed by benzoylation gave the pentasaccharide mixture 14. Selective 2‴-deacetylation of the isolated β-linked 14β with MeCOCl/MeOH/CH 2Cl 2 did not give the expected pentasaccharide acceptor, and serious decomposition occurred, indicating a large steric hindrance at C-2‴. Alternatively, 2,3-di-O-glycosylation of allyl 4,6- O-benzylidene-β- d-glucopyranoside ( 21) with 1 gave 22, then deallylation and trichloroacetimidate formation afforded the trisaccharide donor 24. Condensation of 12 with 24 furnished only the α-linked hexasaccharide 25, and its deprotection gave the free hexaoside 27.

Synthesis of the Glycopeptidolipid of Mycobacterium avium Serovar 4: First Example of a Fully Synthetic C‐Mycoside GPL.

The preparation of the glycopeptidolipid (GPL) present in the cell wall of Mycobacterium aviumSerovar 4, namely 3,4-di-O-Me-alpha-L-Rhap-(1-->1)[R-C(21)H(43)CH(OH)CH(2)CO-D-Phe-[4-O-Me-alpha-L-Rhap-(1-->4)-2-O-Me-alpha-L-Fucp-(1-->3)-alpha-L-Rhap-(1-->2)-6-deoxy-alpha-L-Talp-(1-->3)]-D-allo-Thr-D-Ala-L-Alaol] (1), is described. The synthesis was based on the disconnection of the final structure into four building blocks, an L-rhamnosyl pseudodipeptide, a 6-deoxy-L-talosyl dipeptide, a trisaccharide donor, and a 3-hydroxyalkanoic acid. The key steps are the creation of the glycosidic linkage between the trisaccharide donor, used as a pentenyl glycoside, and the 6-deoxy-L-talose unit of an appropriate D-Phe-O-(6-deoxy-L-talosyl)-D-allo-Thr derivative and the final coupling of the two glycodipeptide fragments. Pentenyl glycosides were shown to provide useful donors in several glycosylation steps. This work constitutes the first synthesis of the full structure of a so-called polar mycoside C GPL.

Synthesis of the glycopeptidolipid of Mycobacterium avium Serovar 4: first example of a fully synthetic C-mycoside GPL.

The preparation of the glycopeptidolipid (GPL) present in the cell wall of Mycobacterium aviumSerovar 4, namely 3,4-di-O-Me-alpha-L-Rhap-(1-->1)[R-C(21)H(43)CH(OH)CH(2)CO-D-Phe-[4-O-Me-alpha-L-Rhap-(1-->4)-2-O-Me-alpha-L-Fucp-(1-->3)-alpha-L-Rhap-(1-->2)-6-deoxy-alpha-L-Talp-(1-->3)]-D-allo-Thr-D-Ala-L-Alaol] (1), is described. The synthesis was based on the disconnection of the final structure into four building blocks, an L-rhamnosyl pseudodipeptide, a 6-deoxy-L-talosyl dipeptide, a trisaccharide donor, and a 3-hydroxyalkanoic acid. The key steps are the creation of the glycosidic linkage between the trisaccharide donor, used as a pentenyl glycoside, and the 6-deoxy-L-talose unit of an appropriate D-Phe-O-(6-deoxy-L-talosyl)-D-allo-Thr derivative and the final coupling of the two glycodipeptide fragments. Pentenyl glycosides were shown to provide useful donors in several glycosylation steps. This work constitutes the first synthesis of the full structure of a so-called "polar mycoside C" GPL.

Synthesis of β‐(1 → 6)‐Branched (1 → 3)‐Glucononaoside with Alternate β‐and α‐Bonds in the Backbone

AbstractLauryl glycoside of β‐D‐Gicp‐(1 → 3)‐[β‐D‐Glcp‐(1 → 6)‐] a‐D‐Glcp‐(1 → 3)‐β‐D‐Glcp‐(1 → 3)‐[β‐D‐Glcp‐(1 → 6)‐] a‐D‐Glcp‐(1 → 3)‐β‐D‐Glcp‐(1 → 3)‐[β‐D‐Glcp‐(1 → 6)‐]β‐D‐Glcp was synthesized through 3 + 3 + 3 strategy. 3‐O‐Allyl‐2, 4, 6‐tri‐O‐benzoyl‐β‐D‐glucopyranosyl‐(1 → 3)‐[2, 3, 4, 6‐tetra‐O‐benzoyl‐β‐D‐glucopyranosyl‐(1 → 6)‐] 1, 2‐O‐isopropylidene‐a‐D‐glucofuranose was used as the key intermediate which was converted to the corresponding trisaccharide donor and acceptor readily.

Synthesis of mannose-containing analogues of (1 → 6)-branched (1 → 3)-glucohexaose

Coupling of the trisaccharide acceptor 2,4,6-tri- O-acetyl-β- d-glucopyranosyl-(1 → 3)-[2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1 → 6)]-5- O-acetyl-1,2- O-isopropylidene-α- d-glucofuranose ( 2 ) with the trisaccharide donor 2,3,4,6-tetra- O-benzoyl-α- d-annopyranosyl-(1 → 3)-[2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1 → 6)]-2,4-di- O-acetyl-α- d-glucopyranosyl trichloroacetimidate ( 1 ) gave an α-linked hexasaccharide 3 , while coupling of 2 with the trisaccharide donor 2,3,4,6-tetra- O-benzoyl-α- d-mannopyranosyl-(1 → 3)-[2,3,4,6-tetra- O-benzoyl-α- d-mannopyranosyl-(1 → 6)]-2,4-di- O-acetyl-α- d-glucopyranosyl trichloroacetimidate ( 7 ) produced α- 8 and β-linked 12 hexasaccharides in a ratio of 3:2. Deprotection of 3 , 8 , and 12 afforded the analogues of the immunomodulator β- d-Glc p-(1 → 3)-[β- d-Glc p-(1 → 6)]-α- d-Glc p-(1 → 3)-β- d-Glc p-(1 → 3)-[β- d-Glc p-(1 → 6)]- d-Glc p ( A ).

A concise synthesis of two isomeric pentasaccharides, the O repeat units from the lipopolysaccharides of P. syringae pv. porri NCPPB 3364 T and NCPPB 3365

A concise synthesis of two isomeric pentasaccharides, α- l-Rha p-(1 → 2)-α- l-Rha p-(1 → 3)-α- l-Rha p-(1 → 3)-[β- d-Glc pNAc-(1 → 2)]-α- l-Rha p ( A ) and α- l-Rha p-(1 → 2)-α- l-Rha p-(1 → 3)-[β- d-Glc pNAc-(1 → 2)]-α- l-Rha p-(1 → 3)-α- l-Rha p ( B ), the O repeats from the lipopolysaccharides of Pseudonomonas syringae pv. porri NCPPB 3364 T and 3365 was achieved via assembly of the building blocks, allyl 3,4-di- O-benzoyl-α- l-rhamnopyranoside ( 1 ), 2,3,4-tri- O-benzoyl-α- l-rhamnopyranosyl trichloroacetimidate ( 2 ), allyl 4- O-benzoyl-3- O-chloroacetyl-α- l-rhamnopyranoside ( 6 ), 3,4,6-tri- O-acetyl-2-deoxy-2-phthalimido-β- d-glucopyranosyl trichloroacetimidate ( 7 ), and allyl 2,4-di- O-benzoyl-α- l-rhamnopyranoside ( 10 ). Coupling of 1 with 2 followed by deallylation and trichloroacetimidate formation gave the disaccharide donor 5 , while condensation of 6 with 7 , followed by dechloroacetylation, offered the disaccharide acceptor 9 . Then, 5 was coupled with 10 to obtain the trisaccharide 11 , and subsequent deallylation and trichloroacetimidate formation furnished the trisaccharide donor 13 . Coupling of 9 with 13 , followed by deprotection, afforded pentasaccharide 19 , while condensation of 9 with 5 , followed by deallylation and trichloroacetimidate formation, gave the tetrasaccharide donor 16 , whose coupling with 10 and subsequent deprotection yielded another pentasaccharide 22 .

Synthesis of β- d-glucose oligosaccharides from Phytophthora parasitica

The glucohexaose, β- d-Glc p-(1→3)-[β- d-Glc p-(1→3)-β- d-Glc p-(1→3)-β- d-Glc p-(1→6)]-β- d-Glc p-(1→3)- d-Glc p, was synthesized as its allyl glycoside via 3+3 strategy. The trisaccharide donor, 2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1→3)-2,4,6-tri- O-acetyl-β- d-glucopyranosyl-(1→3)-2,4,6-tri- O-acetyl-α- d-glucopyranosyl trichloroacetimidate ( 11), was obtained by 3-selective coupling of isopropyl 4,6- O-benzylidene-1-thio-β- d-glucopyranoside ( 2) with 2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1→3)-2- O-acetyl-4,6- O-benzylidene-α- d-glucopyranosyl trichloroacetimidate ( 6), followed by hydrolysis, acetylation, dethiolation, and trichloroacetimidation. Meanwhile, the trisaccharide acceptor, allyl 2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1→3)-2- O-acetyl-β- d-glucopyranosyl-(1→3)-4,6-di- O-acetyl-2- O-benzoyl-α- d-glucopyranoside ( 14), was prepared by coupling of allyl 4,6-di- O-acetyl-2- O-benzoyl-α- d-glucopyranoside ( 12) with 6, followed by debenzylidenation. Condensation of 14 with 11, followed by deacylation, gave the target hexaoside. A β-(1→3)-linked tetrasaccharide 29 was also synthesized with methyl 2- O-benzoyl-4,6- O-benzylidene-β- d-glucopyranosyl-(1→3)-2,4,6-tri- O-acetyl-β- d-glucopyranoside ( 25) as the acceptor and acylated β-(1→3)-linked disaccharide 21 as the donor.

Complex Oligosaccharide Investigations: Synthesis of an Octasaccharide Incorporating the Dimeric Lex Structure of PSGL‐1.

The synthesis of an octasaccharide containing the dimeric Lex oligosaccharide structure found in PSGL-1 carbohydrate chains is reported. Several approaches were investigated employing regioselective and stereoselective glycosylation procedures, and a novel Lewisx trisaccharide donor, 7, was prepared and utilized as a key intermediate building block in the scheme developed for the construction of octasaccharide 3. Toward the preparation of 7, investigations into the influence of different protecting groups upon the relative reactivities of disaccharide acceptor moieties, 25 or 26, and the fucosyl donors, 10 and 11, were conducted using similar glycosylating conditions. Dramatic differences were noted between the effects of electron-donating and electron-withdrawing groups upon the reactivity of the acceptor hydroxyl. A similar effect upon the glycosylating capability of the donor molecule was, likewise, observed. The repeat use of donor 7 was instrumental in the synthesis of the desired dimeric octasacchar...

Synthesis of a hexasaccharide, the repeating unit of O-deacetylated GXM of C. neoformans serotype A

β- d-Glc pA-(1→2)-α- d-Man p-(1→3)-[β- d-Xyl p-(1→2)]-α- d-Man p-(1→3)[-β- d-Xyl p-(1→2)]-α- d-Man p, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A, was synthesized as its allyl glycoside. Thus, 3-O-selective acetylation of allyl 4,6- O-benzylidene-α- d-mannopyranoside afforded 2, and subsequent glycosylation of 2 with 2,3,4-tri- O-benzoyl- d-xylopyranosyl trichloroacetimidate furnished the β-(1→2)-linked disaccharide 4. Debenzylidenation followed by benzoylation gave allyl 2,3,4-tri- O-benzoyl-β- d-xylopyranosyl-(1→2)-3- O-acetyl-4,6-di- O-benzoyl-α- d-mannopyranoside ( 5), and selective 3-O-deacetylation gave the disaccharide acceptor 6. Coupling of 6 with 2- O-acetyl-3,4,6-tri- O-benzoyl-α- d-mannopyranosyl trichloroacetimidate yielded the trisaccharide 8, and subsequent deallylation and trichloroacetimidation gave 2,3,4-tri- O-benzoyl-β- d-xylopyranosyl-(1→2)-[2- O-acetyl-3,4,6-tri- O-benzoyl-α- d-mannopyranosyl-(1→3)]-4,6-di- O-benzoyl-α- d-mannopyranosyl trichloroacetimidate ( 9). Condensation of the trisaccharide donor 9 with the disaccharide acceptor 6 gave the pentasaccharide 10 whose 2-O-deacetylation gave the acceptor 11. Glycosylation of 11 with methyl 2,3,4-tri- O-acetyl-α- d-glucopyranosyluronate trichloroacetimidate and subsequent deprotection gave the target hexasaccharide.

Complex oligosaccharide investigations: synthesis of an octasaccharide incorporating the dimeric Le(x) structure of PSGL-1.

The synthesis of an octasaccharide containing the dimeric Le(x) oligosaccharide structure found in PSGL-1 carbohydrate chains is reported. Several approaches were investigated employing regioselective and stereoselective glycosylation procedures, and a novel Lewis(x) trisaccharide donor, 7, was prepared and utilized as a key intermediate building block in the scheme developed for the construction of octasaccharide 3. Toward the preparation of 7, investigations into the influence of different protecting groups upon the relative reactivities of disaccharide acceptor moieties, 25 or 26, and the fucosyl donors, 10 and 11, were conducted using similar glycosylating conditions. Dramatic differences were noted between the effects of electron-donating and electron-withdrawing groups upon the reactivity of the acceptor hydroxyl. A similar effect upon the glycosylating capability of the donor molecule was, likewise, observed. The repeat use of donor 7 was instrumental in the synthesis of the desired dimeric octasaccharide structure 3. The structure and purity of 3 and important intermediates were fully characterized by DQF-COSY, TOCSY, ROESY, and ESI mass spectroscopy.