galactopyranosylamine as a new chiral Schiff base for asymmetric (2+2) cycloadditions

The importance of carbohydrates for asymmetric synthesis is well recognized [1-4].The reason thatcarbohydrates contain too many chiral centers and functional groups has limited their research aboutstereodifferentiating selection processes in asymmetric synthesis for a long time. During the past decades fewcarbohydrates have received increasing attention as stereodifferentiating auxiliaries in stereoselective syntheses[5]. Carbohydrates have been applied for stereo- and regioselective chemical reactions for last two decades.They could be used for biological recognition on membrane, and they play a prominent role in numerousbiological processes such as tumor-cell growth [6], bacterial and viral infection or inhibition of glycosidases[2,7-9]. Glycosylamines are valuable intermediates in the preparation of nucleosides and drugs [10-12]. It hasbeen proposed that when the Schiff base is derived from an optically active amine and an achiral aldehyde, thedegree of distereoselectivity in the [2+2] cycloaddition varies [13-14]. The asymmetric Staudinger reactionutilizing 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosylamine and 2,3,4,6-tetra-O-pivaloyl-β-D-galactopyranosylamine as the chiral auxiliary in the synthesis of 2-azetidinones has been reported by usand others [15-18]. We now report compound