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Glycosyl Fluorides as Intermediates in BF 3 ·OEt 2 ‐Promoted Glycosylation with Trichloroacetimidates
Author(s) -
Nielsen Michael M.,
Stougaard Bolette A.,
Bols Mikael,
Glibstrup Emil,
Pedersen Christian M.
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201601439
Subject(s) - chemistry , glycosyl , glycosylation , stereospecificity , fluoride , anomer , nuclear magnetic resonance spectroscopy , stereochemistry , glycosyl donor , reaction mechanism , catalysis , organic chemistry , biochemistry , inorganic chemistry
Glycosyl fluorides have been found to be important intermediates in glycosylations with trichloroacetimidate donors and BF 3 · OEt 2 activation (0.2–1 equiv.). Low‐temperature NMR spectroscopy experiments revealed that the α‐trichloroacetimidate was transformed into the glycosyl fluoride with inversion of stereochemistry, whereas the β anomer was not. A concerted mechanism was suggested for the stereospecific formation of glycosyl fluorides, which is not accounted for in the classic mechanism.