ORGANIC
LETTERS
2011
Vol. 13, No. 19
5088–5091
Highly Facialselective Synthesis of
Pyranose 1,3-Oxazines and Their Ring
Opening with Nucleophiles: A Novel Entry
to 2-C-Branched Glycosides
Biao-Lin Yin,*,† Ze-Ren Zhang,† Li-Wen Xu,‡ and Huanfeng Jiang†
School of Chemistry and Chemical Engineering, South China University of Technology,
Guangzhou, Guangdong, 510640, China, and Key Laboratory of Organosilicon
Chemistry and Material Technology of Ministry of Education, Hangzhou Normal
University, Hangzhou, P. R. China
Received July 20, 2011
ABSTRACT
A TMSOTf-promoted cycloaddition of N-benzoyl-N,O-acetals with various glycals and 3-deoxy glycals affords pyranose 1,3-oxazines with high
facial selectivity. In addition, a highly diastereoselective ring opening of the resulting pyranose 1,3-oxazines is reported. With diverse
nucleophiles, these reactions take place upon heating at 80 °C. This novel ring-opening reaction affords structurally diversified 2-C-branched
glycosides with three newly formed contiguous stereocenters.
C-Branched sugars of either natural or synthetic origin
have been the focus of intense studies in carbohydrate
chemistry. Many C-branched sugars in natural antibiotics,
bacterial polysaccharides, and macrolides are often asso-
ciated with specific biological function.1 C-Branched su-
gars have also frequently been used as building blocks for
the total synthesis of natural products and carbohydrate
mimics.2,3 Recently much attention has been paid to
unnatural 2-C-branched sugars, since they have been
found to be mimics of 2-N-acetylsugars for cell surface
engineering and inhibitors of the biosynthesis of lipid.4
However, the synthesis of 2-C-branched sugars is not a
trivial task and problems are frequently encountered with
stereochemical control at the C-branching point and at the
anomeric center.1,5 In addition, multiple-step manipula-
tions and the use of toxic tin, mercury, or strongly basic
organolithium and Grignard reagents are often required
for their synthesis.6 Therefore, an efficient and selective
† South China University of Technology.
‡ Hangzhou Normal University.
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10.1021/ol2019604
Published on Web 09/07/2011
2011 American Chemical Society