New Rearrangements of Hexose 4- and 5-O-Sulfonates

Stevens, Calvin L.; Glinski, Ronald P.; Taylor, K. Grant; Blumbergs, Peter; Sirokmán, F.

doi:10.1021/ja00961a057

Cited by 64 publications

(21 citation statements)

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“…71-73 As with the deamination reactions, this ring contraction with inversion of configuration at C4 in suggests participation by the ring oxygen leading again to an intermediate oxabicyclo[3.1.0]hexyl oxonium ion (Scheme 9). …”

Section: Discussionmentioning

confidence: 92%

Oxidative Deamination ofN-Acetyl Neuraminic Acid: Substituent Effects and Mechanism

Buda

Crich

2016

J. Am. Chem. Soc.

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A study of the mechanism of the oxidative deamination of the N-nitroso-N-acetyl sialyl glycosides leading with overall retention of configuration to the corresponding 2-keto-3-deoxy-d-glycero-d-galacto-nonulopyranosidonic acid (KDN) glycosides is described, making use of a series of differentially O-protected N-nitroso-N-acetyl sialyl glycosides and of isotopic labelling studies. No evidence is found for stereodirecting participation by ester groups at the 4- and 7-positions. Comparisons are drawn with oxidative deamination reactions of 4-amino-4-deoxy and 2-amino-2-deoxy hexopyranosides and a common mechanism is formulated involving the intermediacy of 1-oxabicyclo[3.1.0]hexyl oxonium ions following participation by the pyranoside ring oxygen. A minor reaction pathway has been uncovered by labelling studies in the β-thiosialosides that results in the exchange of the 4-O-acetyl group by the glacial acetic acid that serves as external nucleophile in the general oxidative deamination process. A mechanism is proposed for this exchange involving participation by the thioglycoside at the level of an intermediate diazoalkane.

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Section: Discussionmentioning

confidence: 92%

Oxidative Deamination ofN-Acetyl Neuraminic Acid: Substituent Effects and Mechanism

Buda

Crich

2016

J. Am. Chem. Soc.

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“…This is exemplified by a series of pyranose to furanose ring contractions described by the Stevens and Hanessian laboratories, of which an example is given in Scheme 7. 92–94 A related ring contraction has been reported, but only as a minor product, in a Zbiral-type deamination of an N -acetyl neuraminic acid glycoside. 21 …”

Section: Discussionmentioning

confidence: 96%

Stereoselective Synthesis of 5-epi-α-Sialosides Related to the Pseudaminic Acid Glycosides. Reassessment of the Stereoselectivity of the 5-Azido-5-deacetamidosialyl Thioglycosides and Use of Triflate as Nucleophile in the Zbiral Deamination of Sialic Acids

2016

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With a view to the eventual synthesis of glycosyl donors for the stereocontrolled synthesis of pseudaminic acid glycosides, the stereocontrolled synthesis of a d-glycero-d-gulo sialic acid adamantanylthioglycoside carrying an axial azide at the 5-position is described. The synthesis employs levulinic acid as nucleophile in the oxidative deamination of an N-acetyl neuraminic acid thioglycoside leading to the formation of a 3-deoxy-d-glycero-d-galacto-2-nonulosonic acid (KDN) derivative selectively protected as 5-O-levulinate. Replacement of the levulinate by triflate enables introduction of the axial azide and hence formation of the glycosyl donor. A shorter synthesis uses trifluoromethanesulfonate as nucleophile in the oxidative deamination step when the 5-O-triflyl KDN derivative is obtained directly. Glycosylation reactions conducted with the 5-azido-d-glycero-d-gulo configured sialyl adamantanylthioglycoside at −78 °C are selective for the formation of the equatorial glycosides suggesting that the synthesis of equatorial pseudaminic acid glycosides will be possible as suitable donors become available. A comparable N-acetylneuraminic acid adamantanylthioglycoside carrying an equatorial azide at the 5-position was also found to be selective for equatorial glycoside formation under the same conditions, suggesting that reinvestigation of other azide-protected NeuAc donors is merited. Glycosylation stereoselectivity in the d-glycero-d-gulo series is discussed in terms of the side chain conformation of the donor.

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“…[6] Reduction of 2 with H 2 [7] in the presence of 10% Pd-C gave the 6-deoxy compound (3). Oxidation of 3 with methyl sulfoxide [8] gave a ketohexose, which on reduction with sodium borohydride [8 -10] gave ethyl 6-deoxy-2,3-O-isopropylidene-1-thio-a-D-talopyranoside (4).…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Tetrasaccharide Repeating Unit of the O‐Antigen from Enterohemorrhagic Escherichia coli O157 in the form of its 2‐(trimethylsilyl)ethyl Glycoside

Sarkar

Roy

2006

Journal of Carbohydrate Chemistry

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Two a-linked disaccharide derivatives, ethyl 3,4,6-tri-O-acetyl-2-azido-2-deoxy-a-Dgalactopyranosyl-(1 ! 2)-4-azido-3-O-benzyl-4,6-dideoxy-1-thio-a-D-mannopyranoside (10) and 2- (16), were prepared from appropriate monosaccharide synthons. The disaccharide 16 was deacetylated and debenzoylated to afford the acceptor 17, which was allowed to react with the donor 10 to afford a tetrasaccharide derivative 18. This tetrasaccharide was transformed in three steps into 21, the desired repeating unit of the antigen from enterohemorrhagic E. coli type O157.

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New Rearrangements of Hexose 4- and 5-O-Sulfonates

Cited by 64 publications

References 0 publications

Oxidative Deamination ofN-Acetyl Neuraminic Acid: Substituent Effects and Mechanism

Oxidative Deamination ofN-Acetyl Neuraminic Acid: Substituent Effects and Mechanism

Stereoselective Synthesis of 5-epi-α-Sialosides Related to the Pseudaminic Acid Glycosides. Reassessment of the Stereoselectivity of the 5-Azido-5-deacetamidosialyl Thioglycosides and Use of Triflate as Nucleophile in the Zbiral Deamination of Sialic Acids

Synthesis of Tetrasaccharide Repeating Unit of the O‐Antigen from Enterohemorrhagic Escherichia coli O157 in the form of its 2‐(trimethylsilyl)ethyl Glycoside

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