Stereoselective glycosylations of 2-azido-2-deoxy-glucosides using intermediate sulfonium ions.
TMSOTf-promoted glycosylations of 2-azido-2-deoxy-glucosyl trichloroacetimidates provide excellent alpha-anomeric selectivities when performed at a relatively high reaction temperature in the presence of PhSEt or thiophene. NMR and computation studies have shown that these glycosylations proceed through an equatorial anomeric sulfonium ion, which upon displacement by a sugar alcohol provides an axial glycoside. Computational studies have indicated that steric factors determine the selective formation of the beta-anomeric sulfonium ion.
Park
Jin
J
Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA.
Kawatkar
Sameer
S
Kim
Jin-Hwan
JH
Boons
Geert-Jan
GJ
D001386:Azides / Q000737:chemistry*; D006027:Glycosides / Q000138:chemical synthesis / Q000737:chemistry*; D006031:Glycosylation; D007477:Ions / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D013237:Stereoisomerism; D013452:Sulfonium Compounds / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry
D001386:Azides; D006027:Glycosides; D007477:Ions; D013452:Sulfonium Compounds; D013876:Thiophenes; D010100:Oxygen