Carbanions in Carbohydrate Chemistry: Approaches to Chemical Precursors of <i>C</i>-Nucleosides

Hanessian, Stephen; Pernet, André G.

doi:10.1139/v74-198

Cited by 32 publications

(5 citation statements)

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“…4-Thiogalactofuranose (15) and derivatives were synthesized from readily available and unexpensive methyl -D-glucopyranoside (1). The approach for the synthesis of 15 involved the preparation of a partially protected derivative of 1, having HO-4 free.…”

Section: Resultsmentioning

confidence: 99%

“…The selective benzoylation of methyl a-D-glucopyranoside (1) with TV-benzoylimidazole gave a comparable yield of the tribenzoate 2c but involved less expensive reagents than the stannylation method.148 The use of (19) Bock, K.; Pedersen, C. J. Chem. Soc., Perkin Trans.…”

Section: Resultsmentioning

confidence: 99%

“…However, the synthesis of 4-thio-D-galactofuranose was not reported. This sugar was particularly interesting for us since we have found galactofuranose13 as a constituent of a glycoconjugate from membranes of a parasitic flagellated protozoan, Trypanosoma cruzi, the agent of Chagas' disease, a chronic ailment afflicting several millions in South (1) Horton, D.; Wander, J. The Carbohydrates: Chemistry and Biochemistry; Pigman, W., Horton, D., Eds.…”

Section: Introductionmentioning

confidence: 99%

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A convenient synthesis of 4-thio-D-galactofuranose

Varela¹,

Cicero²,

Lederkremer³

1989

J. Org. Chem.

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The synthesis of 4-thio-D-galactofuranose (15) and derivatives, starting from methyl a-D-glucopyranoside (l), is described. Esterification of 1 with N-benzoylimidazole afforded regioselectively methyl 2,3,6-tri-O-benzoyla-D-glucopyranoside (2c). Further sulfonylation of HO-4 of 2c gave methyl 2,3,6-tri-O-benzoyl-4-O-(p-tolylsulfonyl)-a-Dglucopyranoside (2e) or methyl 2,3,6-tri-O-benzoy1-4-0-[ (p-bromophenyl)sulfonyl]-a-~glucopyanoside (2f). Nucleophilic substitution of the sulfonyloxy group by thiocyanate led to methyl 2,3,6-tri-O-benzoyl-4-deoxy-4-thiocyano-a-~-galactopyranoside (3). This reaction allowed the simultaneous introduction of a group precursor of thiol and the inversion of the configuration a t C-4. Compound 3 was reduced to methyl 4-Sacetyl-2,3,6-tri-0-benzoyl-4-thio-a-~-galactopyranoside (4a) or methyl 2,3,6-tri-0-benzoyl-4-thio-a-~-galactopyranoside (4b). The latter was debenzoylated to give methyl 4-thio-a-~-galactopyranoside (5). This product was also obtained by alkaline methanolysis of 3. Ring contraction was achieved by acetolysis of 5, which produced 1,2,3,5,6-penta-0-acetyl-4-thio-a-~-galactofuranose (10) and its /3-anomer (11) as the main products. The product distribution in the acetolysis reaction of 4-thiopyranose derivatives would depend on the stability of the ionic intermediates involved. 0-Deacetylation of 10 led to 4-thio-~-galactofuranose (15).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A convenient synthesis of 4-thio-D-galactofuranose

Varela¹,

Cicero²,

Lederkremer³

1989

J. Org. Chem.

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“…A general solution for this synthetic problem does not exist as yet. This holds true especially for the common metal-organic reactions as they are Reformatsky reaction [2,3], Knoevenagel reaction [4][5][6][7], allylation [8][9][10][11] or aldol reaction [12].…”

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confidence: 99%

Organocatalyzed Cascade Reaction in Carbohydrate Chemistry

Mahrwald

2015

SpringerBriefs in Molecular Science

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The extensive and extremely strong development of organocatalysis over the last years provided versatile methodologies for convenient utilization of the carbonyl function of unprotected carbohydrates in C-C-bond formation processes. These biomimetic amine-activated mechanisms enable multiple cascade-protocols for the synthesis of a large scope of carbohydrate derived compound classes. Several, only slightly different protocols have been developed for the application of 1.3-dicarbonyls in stereoselective chain-elongation of unprotected carbohydrates and the synthesis of highly functionalized C-glycosides of defined configuration. Furthermore, the latter class of compounds can also be accessed by the use of methyl ketones. So a high substrate scope is available for the installation of desired functionalities in C-glycosides. By a one-pot, operationally simple cascade reaction of isocyanides with unprotected aldoses and amino acids an access to a broad range of defined glycosylated pseudopeptides is given. The elaborated organocatalyzed cascade-reactions provide defined access to highly functionalized carbohydrate derivatives. Depending on the reaction conditions different origin to control the installation of configuration during the bond-formation process were observed. The demonstrated organocatalyzed cascade sequences indicate the great potential of unprotected carbohydrates in the synthesis of highly functionalized bio-mimetic structure motifs by operationally simple, one-pot protocols.Due to the great biological importance of carbon chain elongated carbohydrates, the synthesis of this structural diverse compound class has attracted high synthetic interest from the scientific community. Among the elongated carbohydrates, C-Glycosides have gained considerable importance over the last few decades, since they are configuratively stable under enzymatic conditions and less prone to cleavage at the anomeric carbon. As such they are appealing substrates for chemical biology and medicinal chemistry.

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“…The alP ratio of chlorides increased as the polarity of reaction environments decreased. The most effective alP ratio was 1/4 8. We carried out the chlorination of1-0-acetyl"2,3,5-tri-O-benzoyl-~-D-ribofuranose9.loin a solvent of 1,4-dioxane at 0 ·C for 4-7 days.…”

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confidence: 99%