Synthesis of 2,3,5,6-tetra-O-benzyl-D-galactofuranose for α-glycosidation

Gola, Gabriel; Libenson, Paula; Gandolfi-Donadío, Lucía; Gallo‐Rodriguez, Carola

doi:10.3998/ark.5550190.0006.c18

Cited by 10 publications

(14 citation statements)

References 21 publications

(21 reference statements)

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“…Based in our experience in the one-step anomeric O-alkylation of galactose, 51,52 starting material benzyl α-D-galactofuranoside (13) was obtained crystalline in 67% yield by treatment of galactose with 1.2 equiv. of benzyl bromide and NaH, in DMPU as solvent (Scheme 1).…”

Section: Synthesis Of 11 the Precursor Of The Internal Galfmentioning

confidence: 99%

Synthesis of the O-linked hexasaccharide containing β-d-Galf-(1→2)-β-d-Galf in Trypanosoma cruzi mucins

et al. 2012

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The hexasaccharide β-D-Galp-(1→2)-[β-D-Galp-(1→3)]-β-D-Galp-(1→6)-[β-D-Galf(1→2)-β-D-Galf(1→4)]-D-GlcNAc (1) is the largest carbohydrate structure released as alditol by reductive β-elimination from mucins of some strains of T. cruzi. The terminal β-D-Galp units are sites of sialylation by trans-sialidase which transfers sialic acid from the host to the parasite. Hexasaccharide 1 was synthesized by a [3 + 3]-convergent strategy based on a nitrile assisted glycosylation, using the trichloroacetimidate method. The β-D-Galf-(1→2)-β-D-Galf-D-GlcNAc synthon was sequentially constructed from the reducing end to the non-reducing end employing benzyl α-D-galactofuranoside as starting material for the internal Galf unit. The choice of this novel precursor, obtained in one-reaction step from galactose, allowed the introduction of an orthogonal and participating levulinoyl group at O-2. Thus, the diastereoselective construction of the Galf-β(1→4)-GlcNAc linkage by the trichloroacetimidate method of glycosylation was achieved. The (1)H NMR spectrum of alditol 2 was identical to the product released by β-elimination from the parasite mucin.

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Section: Synthesis Of 11 the Precursor Of The Internal Galfmentioning

confidence: 99%

Synthesis of the O-linked hexasaccharide containing β-d-Galf-(1→2)-β-d-Galf in Trypanosoma cruzi mucins

et al. 2012

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“…The first attempt of deallylation of phosphate 3a was carried out in the presence of a catalytic amount of PdCl 2 (5 mol %) in a mixture DCM/MeOH at room temperature. 24 After a 48 h reaction time, the desired βphosphate 16a was partially decomposed and the isolated yield did not exceed 46% (Table 1, entry 1). Fortunately, increasing the amount of catalyst to 50 mol % improved the yield to 87% by reducing the reaction time to 6 h (Table 1, entry 2).…”

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confidence: 99%

“…The deprotection of the allyl esters is a key step in this strategy because the conditions should be compatible with an azide and the sensitive β-phosphate. The first attempt of deallylation of phosphate 3a was carried out in the presence of a catalytic amount of PdCl 2 (5 mol %) in a mixture DCM/MeOH at room temperature . After a 48 h reaction time, the desired β-phosphate 16a was partially decomposed and the isolated yield did not exceed 46% (Table , entry 1).…”

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A General Strategy to Synthesize ADP-7-Azido-heptose and ADP-Azido-mannoses and Their Heptosyltransferase Binding Properties

Tikad

et al. 2021

Org. Lett.

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The multistep synthesis of a novel ADP-7-azido-7-deoxy-L-glycero-β-D-manno-heptopyranoside 2a and several analogues as heptosyltransferase ligands is described. The synthesis of the key intermediate heptoside-1-β-phosphate 3a involved a βstereoselective phosphorylation of lactol 4 employing diallyl chlorophosphate as a phosphorylating reagent. Five deprotected nucleotide sugars were generated by this synthetic sequence and evaluated as heptosyltransferase substrates (K M , k cat ).

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“…Marino was then employed 280 to synthesise the per-silylated furanoside 19 from Dgalactose 18 (72% yield) (Scheme 4.5). When compared to more traditional syntheses of similar galactofuranosyl donors, which involve a intricate series of protection and deprotection steps, 92,[284][285][286][287] the methodology of Baldoni and Marino was remarkably efficient, with the steric bulk of the TBS-groups being thought to favour formation of the furanose isomer. As seen in Chapter 1 (Section 1.5.5), a methodology that has been used to form galactofuranoses involves an anomeric O-alkylation step.…”

Section: Resultsmentioning

confidence: 99%

“…This is followed by benzylation, deprotection of the anomeric position, and finally imidate formation for later coupling. 92,284 The perbenzoylation of galactose with benzoyl chloride has also been reported to form the furanose. 285 Here a α/β mixture of 56/44 was obtained in 77% yield.…”

Section: Resultsmentioning

confidence: 99%

Purification, Characterisation and Synthesis of Glycerolipids Extracted from L. plantarum and B. longum subsp. infantis

Sauvageau¹

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<p>Glycolipids from the cell wall of Gram-positive bacteria have been the topic of my PhD. It is well known that many bacterial glycolipids (e.g. LPS, TDMs and PIMs) have profound immunological effects, and therefore the characterisation, biological testing and synthesis of gram-positive bacterial glycolipids is of interest. The first part of this thesis includes a description of the extraction and characterisation of glycolipids from gut bacteria including Bifidobacterium and Lactobacillus genus and the second part focussed on the chemical synthesis of Streptococcus sp. DSM 8747 glycolipids and lipoteichoic acid analogues (LTA). Members of the genus Lactobacillus are common in the gut microbiota and are often used as probiotics. As lactobacilli are known to have benefits to human health, compounds on its surface are of high interest. To date, the structures of the glycolipids from L. plantarum have not been conclusively assigned. Thus, for the first time, the full characterisation of the four principal glycolipids of the L. plantarum cell wall was reported using sugar, linkage and FAME analysis, as well as ESI-MS/MS and 1D- and 2D-NMR spectroscopy. The major glycolipids were identified as: α-D-Glcp-diglyceride, α-D-Galp-(1→2)-α-D-Glcp-diglyceride, β-D-Glcp-(1→6)-α-D-Galp-(1→2)-6-O-acyl-α-D-Glcp-diglyceride and β-D-Glcp-(1→6)-α-D-Galp-(1→2)-α-D-Glcp-diglyceride. These glycolipids showed weak activation of murine bone marrow macrophages in an initial biological screen. After having identified the structures of the glycolipids from L. plantarum, the glycolipids from Bifidobacterium, a dominant member of the gut microbiota in infants, were extracted. Bifidobacteria are considered to be important in the development of a healthy immune system and they are believed to exhibit anticancerous properties, alleviate the symptoms of irritable bowel syndrome, and are thought to reduce atopic disease. Despite this, the chemical nature of immunomodulatory compounds on the surface of bifidobacteria has not been well documented. Thus, glycolipids were extracted from B. longum subsp. infantis, fractionated chromatographically and analyzed using NMR spectroscopy, constituent sugar and linkage analysis, and fatty acid analysis. These analyzes revealed a novel glycolipid, containing an unprecedented mixed acetal moiety and a galactofuranose moiety as a head group. However, like L. plantarum glycolipids, bifidobacterial glycolipids were shown only to induce little macrophage activity when tested. Having successfully characterised a novel glycolipid present in bifidobacteria, analogues of this glycolipid as well as poly(glycerophosphate) lipotechoic acids analogues (LTAs) were then synthesised. Much debate still remains about the role of LTAs during Gram-positive bacterial infection. This is partly due to differences in the biological activities of extracted versus synthesised LTAs and highlights the need for structurally defined non-contaminated LTAs when investigating the effect of these glycolipids on the innate immune response. An efficient synthesis of the core lipoteichoic acid (LTA) anchor of the Streptococcus species DSM 8747, and derivatives thereof, was achieved. These Streptococcus glycolipids contain a galactofuranose moiety and thus have similarities to the novel glycolipid that was found in bifidobacteria. The syntheses, which commence with readily available D-galactose, are short (7-9 steps), convergent, and high-yielding (33-37% overall yield). In total 11 different targets were synthesised. The biological activity of these compounds was also investigated, with several analogues (particularly the sn-1,2-di-acylglycerol LTA anchors) found to induce macrophage activation.</p>

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Synthesis of 2,3,5,6-tetra-O-benzyl-D-galactofuranose for α-glycosidation

Cited by 10 publications

References 21 publications

Synthesis of the O-linked hexasaccharide containing β-d-Galf-(1→2)-β-d-Galf in Trypanosoma cruzi mucins

Synthesis of the O-linked hexasaccharide containing β-d-Galf-(1→2)-β-d-Galf in Trypanosoma cruzi mucins

A General Strategy to Synthesize ADP-7-Azido-heptose and ADP-Azido-mannoses and Their Heptosyltransferase Binding Properties

Purification, Characterisation and Synthesis of Glycerolipids Extracted from L. plantarum and B. longum subsp. infantis

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