Stereoselective 1,2-cis Glycosylation of 2-O-Allyl Protected Thioglycosides

The technique of intramolecular aglycon delivery (IAD), whereby a glycosyl acceptor is temporarily appended to a hydroxyl group of a glycosyl donor is an attractive method that can allow the synthesis of 1,2‐cis glycosides in an entirely stereoselective fashion. 2‐O‐Allyl protected thioglycoside don...

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Bibliographic Details
Published in:Chemistry : a European journal 2002-06, Vol.8 (11), p.2608-2621
Main Authors: Aloui, Mahmoud, Chambers, David J., Cumpstey, Ian, Fairbanks, Antony J., Redgrave, Alison J., Seward, Christopher M. P.
Format: Article
Language:English
Subjects:
carbohydrates
Cross-Linking Reagents - chemistry
Disaccharides - chemical synthesis
Disaccharides - chemistry
glycosides
Glycosylation
Oligosaccharides - chemical synthesis
Oligosaccharides - chemistry
Stereoisomerism
stereoselective synthesis
Succinimides - chemistry
Thioglycosides - chemistry
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Summary:The technique of intramolecular aglycon delivery (IAD), whereby a glycosyl acceptor is temporarily appended to a hydroxyl group of a glycosyl donor is an attractive method that can allow the synthesis of 1,2‐cis glycosides in an entirely stereoselective fashion. 2‐O‐Allyl protected thioglycoside donors are excellent substrates for IAD, and may be glycosylated stereoselectively through a three‐step reaction sequence. This sequence consists of quantitative yielding allyl bond isomerisation, to produce vinyl ethers that can then undergo N‐iodosuccinimide mediated tethering of the desired glycosyl acceptor, and subsequent intramolecular glycosylation, to yield either α‐glucosides or β‐mannosides accordingly. Although attempted one‐pot tethering and glycosylation is hampered by competitive intermolecular reaction with excess glycosyl acceptor, this problem can be simply overcome by the use of excess glycosyl donor. Allyl mediated IAD is a widely applicable practical alternative to other IAD approaches for the synthesis of β‐mannosides, that is equally applicable for α‐gluco linkages. It is advantageous in terms of both simplicity of application and yield, and in addition has no requirement for cyclic 4,6‐protection of the glycosyl donor. Allyl protecting group mediated intramolecular aglycon delivery (IAD) of thioglycosides allows the synthesis of β‐mannosides and α‐glucosides (see scheme), either in a one‐ or two‐step procedure, with complete control of anomeric stereochemistry.
ISSN:0947-6539
1521-3765
DOI:10.1002/1521-3765(20020603)8:11<2608::AID-CHEM2608>3.0.CO;2-4