Stereoselective glycosylations of 2-azido-2-deoxy-glucosides using intermediate sulfonium ions |
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Authors: | Park Jin Kawatkar Sameer Kim Jin-Hwan Boons Geert-Jan |
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Institution: | Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA. |
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Abstract: | 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. |
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