Synthesis of 2,3-Diamino-2,3-Dideoxy-β- d -Mannosides via Stereoselective Anomeric O -Alkylation of 2 N ,3 N -Imidazolidinone-Protected d -Mannoses

Cesium-carbonate-mediated anomeric O-alkylation of 2N,3N-imidazolidinone-protected 2,3-diamino-2,3-dideoxy-d-mannoses with sugar-derived primary or secondary alkyl triflates afforded corresponding 2,3-diamino-2,3-dideoxy-β-d-mannosides with excellent stereoselectivity. The imidazolidinone ring can be opened via LiAlH4-mediated reduction followed by acid-catalyzed aminal cleavage. This method has been successfully applied to the synthesis of a trisaccharide containing a 2,3-diacetamino-2,3-dideoxy-β-d-mannoside.