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Neighboring‐Group Participation by C‐2 Ether Functions in Glycosylations Directed by Nitrile Solvents
Author(s) -
Chao ChinSheng,
Lin ChingYu,
Mulani Shaheen,
Hung WeiCheng,
Mong Kwokkong Tony
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201100732
Subject(s) - nitrile , chemistry , ether , anomer , intramolecular force , glycosyl , stereochemistry , lone pair , glycosylation , molecule , solvent , medicinal chemistry , organic chemistry , biochemistry
Ether‐protecting functions at C‐2 hydroxy groups have been found to play participating roles in glycosylations when the reactions are conducted in nitrile solvent mixtures. The participation mechanism is based on intramolecular interaction between the lone electron pair of the oxygen atom of the C‐2 ether function and the nitrile molecule when they are positioned in a cis configuration. A 1,2‐ cis glycosyl oxazolinium intermediate is formed. This participation, in conjunction with the anomeric effect of the glycosyl donor, confers high 1,2‐ trans selectivities on glycosylations. Further application of this concept has led to efficient preparations of α‐(1→5)‐arabinan oligomers.