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Lewis acids as α-directing additives in glycosylations by using 2,3-O-carbonate-protected glucose and galactose thioglycoside donors based on preactivation protocol.
- Source :
-
The Journal of organic chemistry [J Org Chem] 2012 Jun 15; Vol. 77 (12), pp. 5255-70. Date of Electronic Publication: 2012 May 30. - Publication Year :
- 2012
-
Abstract
- Catalytic or stoichiometric amounts of Lewis acids were found to be very effective α-directing additives in the stereoselective glycosylations of diverse 2,3-O-carbonate-protected glucose and galactose thioglycoside donors by preactivation protocol. The poor stereoselectivities of 4,6-di-O-acetyl-2,3-O-carbonate protected thioglycoside donors in glycosyl coupling reactions were greatly improved, and excellent α-stereoselectivities were achieved by the addition of 0.2 equiv of BF(3)·OEt(2). On the other hand, the β-selectivities of 4,6-di-O-benzyl-2,3-O-carbonate-protected thioglucoside donor toward glycosylations were reversed completely to the α-selectivities by the use of 1 equiv of SnCl(4), making the stereoselectivity controllable. Furthermore, the poor stereoselectivities of 4,6-di-O-benzyl-2,3-O-carbonate-protected thiogalactoside donor in glycosylations were also improved by using SnCl(4) as additive.
Details
- Language :
- English
- ISSN :
- 1520-6904
- Volume :
- 77
- Issue :
- 12
- Database :
- MEDLINE
- Journal :
- The Journal of organic chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 22607015
- Full Text :
- https://doi.org/10.1021/jo3002084