Synthesis of N-(2-hydroxy-3-methoxybenzylidene) - 2, 3, 4, 6-tetra-O-acetyl -beta-D 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 that carbohydrates contain too many chiral centers and functional groups has limited their research about stereo differentiating selection processes in asymmetric synthesis for a long time. During the past decades few carbohydrates have received increasing attention as stereo differentiating 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 numerous biological 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 has been proposed that when the Schiff base is derived from an optically active amine and an achiral aldehyde, the degree of distereoselectivity in the [2+2] cycloaddition varies [13-14]. The asymmetric Staudinger reaction utilizing 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 us and others [15-18]. We now report compound 6 as a new chiral auxiliary Schiff base for β-lactam syntheses. © 2005 MDPI. All rights reserved.