One-Pot Synthesis of Substituted Allyl-α-d-Glucopyranosides by an in situ Anomerization Protocol

Charette, André B.; Turcotte, Nathalie; Côté, Bernard

doi:10.1080/07328309408009203

Cited by 18 publications

(6 citation statements)

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“…A vigorously stirred solution of cholesterol (540 mg, 1.40 mmol) and trichloroacetimidate 19 [37,38] (980 mg, 1.54 mmol) in dry CH 2 …”

Section: β-O-(2-o-acetyl-346-tri-o-benzyl-β-d-glucopyranosyl)cholementioning

confidence: 99%

“…In order to probe the influence of the 4a,6a-O-benzylidene group on the trisaccharide formation, the known glucosyl donor 19, [37,38] having benzyl group protection at 4-O and 6-O was employed for the glucosylation of cholesterol providing glucoside 21 in 88 % yield (Scheme 2). Basic cleavage of the 2a-O-acetyl group quantitatively furnished the 2a-O-unprotected derivative 22.…”

Section: Synthesis Of Cholesterol-and Cholestanol-based Saponinsmentioning

confidence: 99%

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Synthesis of Saponins with Cholestanol, Cholesterol, and Friedelanol as Aglycones

et al. 2006

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Procedures for the synthesis of branched Xylβ(1→3)[Galβ(1→2)]‐Glc and Xylβ(1→3)[Galβ(1→2)]‐GlcUA trisaccharides β‐linked to the 3‐O of cholesterol, cholestanol, and friedelanol, respectively, were developed. To this end, β‐selective glucosylation of cholesterol with glucosyl donors giving selective access to 2‐O, 3‐O, and 6‐O was studied. This way intermediates 10 and 21 having 2‐O‐acyl, 3‐O‐benzyl and 4,6‐O‐benzylidene or also benzyl protection were obtained. Removal of the 2‐O‐acyl group and then galactosylation afforded β(1→2)‐linked disaccharide intermediates 14 and 23. Standard manipulations with the O‐benzylidene and/or O‐benzyl protecting groups gave selective access to the 3‐O of the glucosyl residue, thus affording with a xylosyl donor the trisaccharide β‐linked to the cholesteryl residue (compound 18) as decisive intermediate. Also an alternative procedure to this compound via attachement of a Xylβ(1→3)Glc residue to cholesterol and then galactosylation could be developed. Total deprotection of 18 or regioselective introduction of a sulfate group and of a dodecylcarbamoyl residue at 6a‐O furnished saponins 34, 36, and 38, respectively. Hydrogenation of cholesteryl disaccharide 23 led directly to a 3a‐O‐unprotected cholestanyl disaccharide 39. β‐Selective xylosylation and transformation of the liberated glucose hydroxymethyl group into a carboxylic group afforded target molecule 1b having the desired Xyl(1→3)[Gal(1→2)]‐GlcUA β‐linked to cholestanol. Similarly, a saponin analog was obtained having an α‐linked L‐rhamnosyl residue instead of the β‐linked D‐xylosyl residue. Application of the glycosylation sequence, as worked out for cholesterol, to friedelanol led to attachment of the Xylβ(1→3)[Galβ(1→2)]‐Glc residue to the 3‐O (compound 54). Complete O‐deacylation led to saponin 55; oxidation of the hydroxymethyl group of the glucose residue to the carboxylic group and then deprotection afforded target molecule 2 containing the same trisaccharide residue as 1b. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…A vigorously stirred solution of cholesterol (540 mg, 1.40 mmol) and trichloroacetimidate 19 [37,38] (980 mg, 1.54 mmol) in dry CH 2 …”

Section: β-O-(2-o-acetyl-346-tri-o-benzyl-β-d-glucopyranosyl)cholementioning

confidence: 99%

Section: Synthesis Of Cholesterol-and Cholestanol-based Saponinsmentioning

confidence: 99%

Synthesis of Saponins with Cholestanol, Cholesterol, and Friedelanol as Aglycones

et al. 2006

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“…The synthesis of the tetrasaccharide 1 and its close structural analog 2 as their 4-methoxyphenyl glycosides was achieved by series of stereoselective glycosylations of a number of suitably functionalized monosaccharide derivatives 4 , 5 [18] , 6 , 7 , 8 [19] , and 9 [20] prepared from the commercially available reducing sugars using synthetic methodologies reported earlier. Since, the preparation of β-linked d -mannose moiety from d -mannose and α- d -glucosamine moiety from d -glucosamine are challenging issues, these two moieties are successfully prepared using β- d -glucosyl moiety and α- d -mannosyl moiety respectively as the precursors after completion of the glycosylations with required stereochemical outcome.…”

Section: Resultsmentioning

confidence: 99%

“…Stereo selective glycosylation of compound 4 with glucosyl trichloroacetimidate derivative 5 [18] in the presence of trifluoromethane sulfonic acid (TfOH) [25] furnished 4-methoxyphenyl (2- O -acetyl-3,4,6-tri- O -benzyl-β- d -glucopyranosyl)-(1→4)-3- O -allyl-2,6-di- O -benzyl-α- d -galactopyranoside ( 10 ) in 72% yield. Formation of compound 10 was confirmed from its spectral analysis [δ 5.24 (d, J = 3.5 Hz, H-1 A ), 4.61 (d, J = 8.0 Hz, H-1 B ) in the 1 H NMR and δ 101.8 (C-1 B ), 97.4 (C-1 A ) in the 13 C NMR spectra].…”

Section: Resultsmentioning

confidence: 99%

Synthesis of the Tetrasaccharide Motif and Its Structural Analog Corresponding to the Lipopolysaccharide of Escherichia coli O75

Misra

2012

PLoS ONE

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BackgroundExtraintestinal pathogenic E. coli are mostly responsible for a diverse spectrum of invasive human and animal infections leading to the urinary tract infections. Bacterial lipopolysaccharides are responsible for their pathogenicity and their interactions with host immune responses. In spite of several breakthroughs in the development of therapeutics to combat urinary tract infections and related diseases, the emergence of multidrug-resistant bacterial strains is a serious concern. Lipopolysaccharides are attractive targets for the development of long-term therapeutic agents to eradicate the infections. Since the natural sources cannot provide the required amount of oligosaccharides, development of chemical synthetic strategies for their synthesis is relevant to gain access to a reservoir of oligosaccharides and their close analogs.MethodologyTwo tetrasaccharide derivatives were synthesized from a single disaccharide intermediate. β-d-mannoside moiety was prepared from β-d-glucoside moiety following oxidation–reduction methodology. A [2+2] stereoselective block glycosylation strategy has been adopted for the preparation of tetrasaccharide derivative. α-d-Glucosamine moiety was prepared from α-d-mannosidic moiety following triflate formation at C-2 and SN 2 substitution. A one-pot iterative glycosylation exploiting the orthogonal property of thioglycoside was carried out during the synthesis of tetrasaccharide analog.ResultsSynthesis of the tetrasaccharide motif (1) and its structural analog (2) corresponding to the lipopolysaccharide of Escherichia coli O75 was successfully achieved in excellent yield. Most of the reactions are clean and high yielding. Both compounds 1 and 2 were synthesized as their 4-methoxyphenyl glycoside, which can act as a temporary anomeric protecting group for further use of these tetrasaccharides in the preparation of glycoconjugates.

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“…102 Steroids bearing a hydroxy group at a position other than C-3 have also been glycosylated by the acetimidate method. 103 For instance, a steroidal trisaccharide saponin possessing strong anti-inflammatory and immunopharmacological activities has been prepared under Schmidt's 'inverse procedure', 104 which consists of a previous activation of the alcohol by treatment with TMSOTf before adding the imidate, whilst the normal procedure of glycosylation failed owing to the steric hindrance of 1-OH (Scheme 55).…”

Section: Trihalogenoacetimidatesmentioning

confidence: 99%

The glycosylation of steroids

Pellissier

2004

Tetrahedron

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One-Pot Synthesis of Substituted Allyl-α-d-Glucopyranosides by an in situ Anomerization Protocol

Cited by 18 publications

References 0 publications

Synthesis of Saponins with Cholestanol, Cholesterol, and Friedelanol as Aglycones

Synthesis of Saponins with Cholestanol, Cholesterol, and Friedelanol as Aglycones

Synthesis of the Tetrasaccharide Motif and Its Structural Analog Corresponding to the Lipopolysaccharide of Escherichia coli O75

The glycosylation of steroids

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