Selective Glycosylations with Furanosides

Gallo‐Rodriguez, Carola; Kashiwagi, Gustavo A.

doi:10.1002/9783527696239.ch14

Cited by 11 publications

(15 citation statements)

References 135 publications

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“…1 , 2 Such species are most conveniently obtained by chemical synthesis, and over the past several years many methods for accessing furanose-containing glycans have been developed. 5 , 6 …”

Section: Introductionmentioning

confidence: 99%

“… 5 Consequently, the majority of robust methods for the stereocontrolled synthesis of 1,2- cis -furanosides employ conformationally locking groups resulting in a single energetically favored reaction pathway. 5 , 6 Such methods have previously been applied to the synthesis of β-arabinofuranosides ( 3 , Figure 1 B), 7 − 9 β-fructofuranosides ( 4 ), 10 and α-galactofuranosides ( 5 ). 11 − 13 …”

Section: Introductionmentioning

confidence: 99%

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Stereocontrolled Synthesis of α-Xylofuranosides Using a Conformationally Restricted Donor

et al. 2018

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A number of biologically relevant glycoconjugates possess 1,2-cis-furanosidic linkages, a class of glycosidic bond that remains challenging to introduce with high stereoselectivity. In this paper, we report an approach to one family of such linkages, α-xylofuranosides, via the use of thioglycoside donors possessing a conformationally restricting xylylene protecting group. The method was shown to provide the desired targets in good to excellent yield and stereoselectivity. Computational investigations support the proposal that the protecting group locks the electrophilic intermediate in these reactions into a conformation that leads to the high selectivity. The power of the methodology was demonstrated through the synthesis of a complex hexasaccharide motif from lipoarabinomannan, an immunomodulatory polysaccharide from mycobacteria.

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“…1 , 2 Such species are most conveniently obtained by chemical synthesis, and over the past several years many methods for accessing furanose-containing glycans have been developed. 5 , 6 …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stereocontrolled Synthesis of α-Xylofuranosides Using a Conformationally Restricted Donor

et al. 2018

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“…The synthesis of furanose-containing oligosaccharides is an important area of current research because monosaccharides in the furanose form are frequent constituents of the polysaccharides of pathogenic microorganisms, such as extracellular galactomannan of Aspergillus fumigatus , , the arabinogalactan of Mycobacterium tuberculosis and other Mycobacterium species, − the galactan of Actinobacillus pleuropneumoniae , and the galactan of Bifidobacterium catenulatum . Several methods to access furanosyl building blocks have been reported . Because of the lower number of strategies available for the preparation of furanosides, in comparison to pyranosides, the search for simple efficient and reliable methods for the synthesis of selectively functionalized furanoside glycosyl donors still presents a challenge.…”

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confidence: 99%

“…10 Several methods to access furanosyl building blocks have been reported. 11 Because of the lower number of strategies available for the preparation of furanosides, in comparison to pyranosides, the search for simple efficient and reliable methods for the synthesis of selectively functionalized furanoside glycosyl donors still presents a challenge.…”

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confidence: 99%

A Ring Contraction of 2,3-Di-O-Silylated Thiopyranosides To Give Thiofuranosides under Mildly Acidic Conditions

et al. 2018

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A pyranose ring contraction of ethyl 1-thio-β-d-galactopyranosides has been discovered that proceeds with retention of aglycon under mildly acidic conditions (aq TFA in CH2Cl2). Key factors for success of this rearrangement are the presence of bulky silyl (TIPS or TBDPS) substituents at both O-2 and O-3 and a free hydroxy group at C-4 (derivatives with acid-labile protective groups at O-4 will also engage in this reaction). The rearrangement cleanly proceeds for 2,3-di-O-TIPS derivatives with two hydroxy groups at C-4 and C-6, acid-labile TES groups at O-4 and O-6, or one acyl substituent (Bz, ClAc) at O-6. A possibility to switch the direction of the debenzylidenation reaction in 4,6-O-benzylidene-2,3-di-O-TIPS/TBDPS derivatives by the choice of an acid (TFA, which cleanly gives furanose, versus AcOH, which cleaves benzylidene acetal only) may present an advantage in the divergent synthesis of selectively protected glycosyl donors (either in furanose or pyranose form) useful for the synthesis of biologically important oligosaccharides.

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“…Synthesis of 1,2- cis -furanosides can prove challenging as it can be difficult to control the stereochemistry at the anomeric centre [ 27 , 28 ]. Unless indirect glycosylation approaches are used [ [29] , [30] , [31] ], application of non-participating protecting groups remains the main method of minimising the formation of 1,2- trans -glycofuranosylation products.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of glyceryl glycosides related to A-type prymnesin toxins

Hems

Nepogodiev

Rejzek

et al. 2018

Carbohydrate Research

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A suite of glycosylated glycerol derivatives representing various fragments of the glycosylated ichthyotoxins called prymnesins were chemically synthesised. Glycerol was used to represent a small fragment of the prymnesin backbone, and was glycosylated at the 2° position with the sugars currently reported to be present on prymnesin toxins. Neighbouring group participation was utilised to synthesise 1,2-trans-glycosides. SnCl2-promoted glycosylation with furanosyl fluorides gave 1,2-cis-furanosides with moderate stereocontrol, whilst TMSOTf promoted glycosylation with a furanosyl imidate gave a 1,2-cis-furanoside with good stereocontrol. The chemical synthesis of two larger glyceryl diglycoside fragments of prymnesin-1, glycosylated with α-ʟ-arabinopyranose and α-ᴅ-ribofuranose, is also described. As the stereochemistry of the prymnesin backbones at this region is undefined, both the 2R- and 2S- glycerol isomers were synthesised. The separated diastereoisomers were distinguished by comparing NOESY NMR with computational models.

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Selective Glycosylations with Furanosides

Cited by 11 publications

References 135 publications

Stereocontrolled Synthesis of α-Xylofuranosides Using a Conformationally Restricted Donor

Stereocontrolled Synthesis of α-Xylofuranosides Using a Conformationally Restricted Donor

A Ring Contraction of 2,3-Di-O-Silylated Thiopyranosides To Give Thiofuranosides under Mildly Acidic Conditions

Synthesis of glyceryl glycosides related to A-type prymnesin toxins

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