Stereoselective Synthesis of β-D-Mannopyranosides with Reactive Mannopyranosyl Donors Possessing a Neighboring Electron-Withdrawing Group This work was supported by the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie, and the European Community (Grant No. HPRN-CT-2000-00001/GLYCOTRAIN). A.A.H.A.R. and E. S. H. El Ashry are grateful to the Alexander von Humboldt Foundation for a fellowship and for the continued support, respectively.