β-Mannosylation with 4,6-benzylidene protected mannosyl donors without preactivation

Heuckendorff, Mads; Bols, Pernille S.; Barry, Collin Bartholomew; Frihed, Tobias Gylling; Pedersen, Christian; Bols, Mikael

doi:10.1039/c5cc04716a

Cited by 38 publications

(36 citation statements)

References 41 publications

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“…Great progress has been achieved, especially by the Crich group, who in numerous articles have improved and thoroughly investigated this particular coupling. [48,52,53] We decided to investigate whether the new donor motif could be used in -selective mannosylation. [49][50][51] It is believed that for success in this coupling, it is crucial for the donor to have a 4,6-O-benzylidene group, and also the donor must be preactivated at low temperature.…”

Section: Resultsmentioning

confidence: 99%

Glycosyl ortho‐Methoxybenzoates: Catalytically Activated Glycosyl Donors with an Easily Removable and Recyclable Leaving Group

et al. 2016

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We describe the β‐ortho‐methoxybenzoate as a shelf stable and practical C‐1 nucleofuge for catalytic chemical glycosylation in which the benzoic acid by‐product can be easily removed, reisolated, and potentially recycled after the glycosylation reaction. This new type of glycosyl donor can be efficiently activated by a range of promoters, including Bi(OTf)3, Fe(OTf)3, TMSOTf (TMS = trimethylsilyl), and triflic acid, with low (<10 mol‐%) catalyst loadings. The donor shows higher reactivity than analogous benzoate, p‐methoxybenzoate and p‐cyano‐o‐methoxybenzoate donors. In glycosylation reactions with o‐methoxybenzoate donors, the yields of disaccharide products were good to excellent for various glycosyl acceptors, including a carbohydrate‐based secondary alcohol. Furthermore, β‐selective mannosylation was achieved with a Crich‐type donor at 0 °C to ambient temperature, without donor preactivation. The donor was also used for the first step of a one‐pot two‐step glycosylation to obtain a trisaccharide; the second coupling involved activation of a thioglycoside with NIS/TMSOTf (NIS = N‐iodosuccinimide). We believe that this offers a good alternative to current protocols.

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Section: Resultsmentioning

confidence: 99%

Glycosyl ortho‐Methoxybenzoates: Catalytically Activated Glycosyl Donors with an Easily Removable and Recyclable Leaving Group

et al. 2016

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“…74 In a follow up to this work Bols and coworkers applied similar conditions, catalytic in triflate, to the activation of 4,6- O -benzylidene protected mannosyl thioglycosides and sulfoxides with comparable results. 75 Also studied was the activation of a 4,6- O -benzylidene protected α-trichloroacetimidate with BF 3 OEt 2 in the presence and absence of triflate. In the complete absence of triflate, β-mannosides were not formed owing to the well-known competing abstraction of fluoride from the reagent, 76 but β-mannoside formation was restored on addition of lithium triflate, ultimately leading the authors to remark on the beneficial catalytic effect of the triflate ion.…”

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confidence: 99%

“…In the complete absence of triflate, β-mannosides were not formed owing to the well-known competing abstraction of fluoride from the reagent, 76 but β-mannoside formation was restored on addition of lithium triflate, ultimately leading the authors to remark on the beneficial catalytic effect of the triflate ion. 75 …”

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confidence: 99%

Trifluoromethanesulfonate Anion as Nucleophile in Organic Chemistry

2017

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Although the triflate ion is not generally perceived as a nucleophile many examples of its behavior as such exist in the literature. This synopsis presents an overview of such reactions, in which triflate may be either a stoichiometric or catalytic nucleophile, leading to the suggestion that nucleophilic catalysis by triflate may be more common than generally accepted, albeit hidden by the typical reactivity of organic triflates which complicates their observation as intermediates.

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“…On the other hand, Schmidt showed19a that a 4,6‐ O ‐benzylidene‐protected mannosyl trichloroacetimidate provided the same β‐selectivity of mannosylation without preactivation (see also a review16). Very recently, when this communication was being prepared, Bols and co‐workers published similar results 19b…”

Section: Resultsmentioning

confidence: 53%

A Blockwise Approach to the Synthesis of (1→2)‐Linked Oligosaccharides Corresponding to Fragments of the Acid‐Stable β‐Mannan from the Candida albicans Cell Wall

et al. 2016

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Oligomannosides comprising short β‐(1→2)‐oligomannosyl blocks attached through a glycoside bond to an α‐(1→2)‐linked oligomannoside are a constituent of side chains of the mannan from the Candida cell wall. This type of oligomannoside is known as an acid‐stable β‐mannan and corresponds to the antigenic factor 6. In this communication, we report a convergent blockwise synthesis of four spacer‐armed oligomannosides of this type including from 1 to 4 β‐mannosyl and 2–3 α‐mannosyl residues. β‐(1→2)‐Oligomannosyl thioglycosides and sulfoxides containing up to four mannose units were employed for introduction of β‐oligomannoside sequences. The efficiency of β‐mannosylation with mono‐ and oligomannoside donors was shown to depend more on the structure of the reaction partners than on the applied activation protocol. The oligomannosides obtained will be used to prepare various molecular tools for investigation of the Candida cell wall.

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β-Mannosylation with 4,6-benzylidene protected mannosyl donors without preactivation

Abstract: Mannosylations with benzylidene protected mannosyl donors were found to be β-selective even when no preactivation was performed. It was also found that the kinetic β-product in some cases anomerizes fast to the thermodynamically favored α-anomer under typical reaction conditions.

Cited by 38 publications

References 41 publications

Glycosyl ortho‐Methoxybenzoates: Catalytically Activated Glycosyl Donors with an Easily Removable and Recyclable Leaving Group

Glycosyl ortho‐Methoxybenzoates: Catalytically Activated Glycosyl Donors with an Easily Removable and Recyclable Leaving Group

Trifluoromethanesulfonate Anion as Nucleophile in Organic Chemistry

A Blockwise Approach to the Synthesis of (1→2)‐Linked Oligosaccharides Corresponding to Fragments of the Acid‐Stable β‐Mannan from the Candida albicans Cell Wall

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β-Mannosylation with 4,6-benzylidene protected mannosyl donors without preactivation

Abstract: Mannosylations with benzylidene protected mannosyl donors were found to be β-selective even when no preactivation was performed. It was also found that the kinetic β-product in some cases anomerizes fast to the thermodynamically favored α-anomer under typical reaction conditions.

Cited by 38 publications

References 41 publications

Glycosyl ortho‐Methoxybenzoates: Catalytically Activated Glycosyl Donors with an Easily Removable and Recyclable Leaving Group

Glycosyl ortho‐Methoxybenzoates: Catalytically Activated Glycosyl Donors with an Easily Removable and Recyclable Leaving Group

Trifluoromethanesulfonate Anion as Nucleophile in Organic Chemistry

A Blockwise Approach to the Synthesis of (1→2)‐Linked Oligosac­char­ides Corresponding to Fragments of the Acid‐Stable β‐Mannan from the Candida albicans Cell Wall

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A Blockwise Approach to the Synthesis of (1→2)‐Linked Oligosaccharides Corresponding to Fragments of the Acid‐Stable β‐Mannan from the Candida albicans Cell Wall