Highly Regio- and Stereoselective Synthesis of Bioactive Oligosaccharides Using 1,2-<i>O</i>-Ethylidene-α-<scp>d</scp>-gluco- and -β-<scp>d</scp>-Mannopyranose as the Acceptors and Acetobromosugars as the Donors via Ortho Ester Intermediates

Wei, Wang; Kong, Fanzuo

doi:10.1021/jo982508e

Cited by 29 publications

(13 citation statements)

References 29 publications

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“…Deacetylation of α , α - 21b (22 mg, 0.018 mmol) in ethanolic ammonia by the procedure for obtaining triol 16b and isolation of product by crystallization from MeOH led to octaol 21c (10 mg, 56%) as colorless needles: mp 280 °C (dec) (CH 3 OH); [α] 24 D −22.0 ( c 0.05, pyridine); IR (film) ν max 3406, 2927, 1645, 1404, 1036 cm −1 ; 1 H NMR (C 5 D 5 N, 400 MHz) δ 0.91–2.50 (28H, m), 1.34 (6H, s, H-18), 1.41 (6H, s, H-19), 1.63 (6H, d, J 5.6, H-6′), 2.75 (2H, dd, J 5.6, 18.0, H-1α), 2.87 (2H, d, J 16.4, H-4 β ), 3.01 (2H, dd, J 5.6, 18.0, H-1 β ), 3.59 (2H, d, J 16.4, H-4 α ), 4.27–4.31 (6H, m, H-4′, H-5′, H-21), 4.25–4.54 (2H, d, J 3.2, 8.4, H-3′), 4.56 (2H, s, H-2), 4.68–4.71 (4H, m, H-11, H-21), 5.35 (2H, s, H-1′), 5.42 (2H, t, J 6.8, H-20), 5.71 (2H, d, J 2.8, OH, exch. D 2 O), 6.63 (3H, br, OH, exch.…”

Section: Methodsmentioning

confidence: 99%

The Cephalostatins. 21. Synthesis of Bis-steroidal Pyrazine Rhamnosides

et al. 2011

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The synthesis of bis-steroidal pyrazines derived from 3-oxo-11,21-dihydroxy-pregna- 4,17(20)-diene (4) and glycosylation of a D-ring side chain with α-L-rhamnose has been summarized. Rearrangment of steroidal pyrazine 10 to 14 was found to occur with boron triflouride etherate. Glycosylation of pyrazine 10 using 2,3,4-tri-O-acetyl-α-L-rhamnose iodide led to 1,2-orthoester-α-L-rhamnose pyrazine 17b. By use of a persilylated α-L-rhamnose iodide as donor, formation of the orthoester was avoided. Bis-steroidal pyrazine 10 and rhamnosides 17b and 21c were found to significantly inhibit cancer cell growth in a murine and human cancer cell line panel. Pyrazine 9 inhibited growth of the nosocomial pathogen Enterococcus faecalis.

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Section: Methodsmentioning

confidence: 99%

The Cephalostatins. 21. Synthesis of Bis-steroidal Pyrazine Rhamnosides

et al. 2011

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“…Various conventional strategies were applied to the chemical preparation of -glucans, and to linear and 3-branched -(1,6)-glucans [67][68][69][70][71]. Amongst these studies, innovative approaches in glycochemistry were proposed, and notably supported synthesis [72], methodology using rearrangement of intermediate orthoesters [73,74], one-pot glycosylation methodology [75][76][77][78] and iterative methods based on orthogonal activation of -bromoglycosides derived from -selenoglycosides (Fig. 4) [68].…”

Section: Chemical Approachesmentioning

confidence: 99%

Recent Progress in the Field of β-(1,3)-Glucans and New Applications

Descroix¹,

Ferrières²,

Jamois³

et al. 2006

MRMC

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Beta-(1,3)-glucans are widely distributed within microorganisms or seaweeds in which they act as membrane components or for energy storage, respectively. Since these glucans are not biosynthesized by mammals, they are likely to activate the immune system of their host. Since the discovery of their positive involvement as immunomodulator agents, numerous studies were published all around the glycosciences. These works deal with purification procedures, analytical chemistry, synthetic processes, chemical modification of the natural polysaccharides, determination of their physicochemical properties, and assessment of their biological and medicinal effects through in vitro and in vivo studies. This article aims at presenting some recent results linked to beta-(1,3)-glucans through two closely connected points of view, i.e. biology and chemistry. Biological aspects will be focused more particularly on discovery of some receptors present on immunocompetent cells and scope and limitations of chemical synthesis and/or modifications will be described. Moreover, this paper will also introduce some new chemo-enzymatic synthetic methods using wild-type or mutant glycosidases and will be extended to novel opportunities of applications of beta-(1,3)-glucans in nanotechnology resulting from a better understanding of their self-assembling propensity in aqueous media.

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“…Problems of solubility of the methyl glycopyranoside acceptors in this method were overcome by the use of 1,2-ethylidene protection. 162 This method has also allowed the formation of a hexasaccharide phytoalexin inhibitor based on the synthesis of a 3,6-branched β-triglucoside motif which was formed through the regioselective formation of a 3,6-diorthoester. 162 An important example of OH activation is illustrated by the use of the intermediate trityl ether monosaccharide acceptor in Scheme 16.…”

Section: Exploiting Reactivity Tuning and Inherent Reactivitiesmentioning

confidence: 99%

“…162 This method has also allowed the formation of a hexasaccharide phytoalexin inhibitor based on the synthesis of a 3,6-branched β-triglucoside motif which was formed through the regioselective formation of a 3,6-diorthoester. 162 An important example of OH activation is illustrated by the use of the intermediate trityl ether monosaccharide acceptor in Scheme 16. This allowed selective galactosylation of the secondary O-4 over primary O-6.…”

Section: Exploiting Reactivity Tuning and Inherent Reactivitiesmentioning

confidence: 99%

Recent developments in oligosaccharide synthesis

Davis

2000

J. Chem. Soc., Perkin Trans. 1

272

132

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Introduction 2 Glycosyl donors 2.1 Thio/selenoglycosides 2.2 Sulfoxides 2.3 Glycals 2.4 Trichloroacetimidates 2.5 Pent-n-enyl glycosides 2.6 Halides 2.7 Orthoesters and acetates 2.8 Vinyl glycosides 2.9 Anomeric phosphorus containing compounds 2.10 Anomeric sulfonates 2.11 Other donor types 3 Strategies for stereoselective formation of anomeric bond 3.1 Choice according to stereochemistry and functionality at C-1 and C-2 3.2 Anchimeric assistance or neighbouring group participation (NGP) 3.3 Non-participatory glycosylations 3.4 Intramolecular aglycon delivery (IAD) 3.5 Non-glycosyl cation based approaches 4 Chemoselectivity 4.1 Armed/disarmed 4.2 Active/latent: the effects of leaving group 4.3 Orthogonal glycosylations 4.4 Reactivity tuning and one-pot reactions 5 Regioselectivity 5.1 Protecting groups 5.2 Exploiting reactivity tuning and inherent reactivities 5.3 Intramolecular aglycon delivery (IAD) 5.4 One-pot methods 6 Higher sugars 7 2-Deoxy sugars 8 Enzymatic methods 8.1 Glycosidases 8.2 Glycosyltransferases 9 Polymer supported methods and library syntheses 10 Conclusions and future directions 11 References

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Highly Regio- and Stereoselective Synthesis of Bioactive Oligosaccharides Using 1,2-O-Ethylidene-α-d-gluco- and -β-d-Mannopyranose as the Acceptors and Acetobromosugars as the Donors via Ortho Ester Intermediates

Cited by 29 publications

References 29 publications

The Cephalostatins. 21. Synthesis of Bis-steroidal Pyrazine Rhamnosides

The Cephalostatins. 21. Synthesis of Bis-steroidal Pyrazine Rhamnosides

Recent Progress in the Field of β-(1,3)-Glucans and New Applications

Recent developments in oligosaccharide synthesis

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Highly Regio- and Stereoselective Synthesis of Bioactive Oligosaccharides Using 1,2-O-Ethylidene-α-d-gluco- and -β-d-Mannopyranose as the Acceptors and Acetobromosugars as the Donors via Ortho Ester Intermediates

Cited by 29 publications

References 29 publications

The Cephalostatins. 21. Synthesis of Bis-steroidal Pyrazine Rhamnosides

The Cephalostatins. 21. Synthesis of Bis-steroidal Pyrazine Rhamnosides

Recent Progress in the Field of &#946;-(1,3)-Glucans and New Applications

Recent developments in oligosaccharide synthesis

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Recent Progress in the Field of β-(1,3)-Glucans and New Applications