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Stereoselective C-glycoside formation with 2-O-benzyl-4,6-O-benzylidene protected 3-deoxy gluco- and mannopyranoside donors: comparison with O-glycoside formation.
J Org Chem. 2012 Oct 19; 77(20):8905-12.JO

Abstract

Unlike alcohols, the reaction of C-nucleophiles with 2-O-benzyl-4,6-O-benzylidene-protected 3-deoxy-gluco- and mannopyranosyl thioglycosides is highly stereoselective providing the α-C-glycosides in the gluco-series and the β-C-glycosides in the manno-series. Conformational analysis of nucleophilic attack of putative intermediate glycosyl oxocarbenium ions suggests that the observed selectivities for C-glycoside formation can be explained by preferential attack on the opposite face of the oxocarbenium to the C2-H2 bond and that eclipsing interactions with this bond are the main stereodetermining factor. It is argued that the steric interactions in the attack of alcohols (sp(3)-hybridized O) and of typical carbon-based nucleophiles (sp(2) C) on oxocarbenium ions are very different, with the former being less severe, and thus that there is no a priori reason to expect O- and C-glycosylation to exhibit parallel stereoselectivities for attack on a given oxocarbenium ion.

Authors+Show Affiliations

Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA.No affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

23009024

Citation

Moumé-Pymbock, Myriame, and David Crich. "Stereoselective C-glycoside Formation With 2-O-benzyl-4,6-O-benzylidene Protected 3-deoxy Gluco- and Mannopyranoside Donors: Comparison With O-glycoside Formation." The Journal of Organic Chemistry, vol. 77, no. 20, 2012, pp. 8905-12.
Moumé-Pymbock M, Crich D. Stereoselective C-glycoside formation with 2-O-benzyl-4,6-O-benzylidene protected 3-deoxy gluco- and mannopyranoside donors: comparison with O-glycoside formation. J Org Chem. 2012;77(20):8905-12.
Moumé-Pymbock, M., & Crich, D. (2012). Stereoselective C-glycoside formation with 2-O-benzyl-4,6-O-benzylidene protected 3-deoxy gluco- and mannopyranoside donors: comparison with O-glycoside formation. The Journal of Organic Chemistry, 77(20), 8905-12. https://doi.org/10.1021/jo3011655
Moumé-Pymbock M, Crich D. Stereoselective C-glycoside Formation With 2-O-benzyl-4,6-O-benzylidene Protected 3-deoxy Gluco- and Mannopyranoside Donors: Comparison With O-glycoside Formation. J Org Chem. 2012 Oct 19;77(20):8905-12. PubMed PMID: 23009024.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Stereoselective C-glycoside formation with 2-O-benzyl-4,6-O-benzylidene protected 3-deoxy gluco- and mannopyranoside donors: comparison with O-glycoside formation. AU - Moumé-Pymbock,Myriame, AU - Crich,David, Y1 - 2012/10/11/ PY - 2012/9/27/entrez PY - 2012/9/27/pubmed PY - 2013/3/23/medline SP - 8905 EP - 12 JF - The Journal of organic chemistry JO - J. Org. Chem. VL - 77 IS - 20 N2 - Unlike alcohols, the reaction of C-nucleophiles with 2-O-benzyl-4,6-O-benzylidene-protected 3-deoxy-gluco- and mannopyranosyl thioglycosides is highly stereoselective providing the α-C-glycosides in the gluco-series and the β-C-glycosides in the manno-series. Conformational analysis of nucleophilic attack of putative intermediate glycosyl oxocarbenium ions suggests that the observed selectivities for C-glycoside formation can be explained by preferential attack on the opposite face of the oxocarbenium to the C2-H2 bond and that eclipsing interactions with this bond are the main stereodetermining factor. It is argued that the steric interactions in the attack of alcohols (sp(3)-hybridized O) and of typical carbon-based nucleophiles (sp(2) C) on oxocarbenium ions are very different, with the former being less severe, and thus that there is no a priori reason to expect O- and C-glycosylation to exhibit parallel stereoselectivities for attack on a given oxocarbenium ion. SN - 1520-6904 UR - https://www.unboundmedicine.com/medline/citation/23009024/Stereoselective_C_glycoside_formation_with_2_O_benzyl_46_O_benzylidene_protected_3_deoxy_gluco__and_mannopyranoside_donors:_comparison_with_O_glycoside_formation_ L2 - https://dx.doi.org/10.1021/jo3011655 DB - PRIME DP - Unbound Medicine ER -