Synthesis of beta-D galactopyranosyl amino-(N-salicylidene)-2, 3, 4, 6-tetra-O-acetate as a new chiral Schiff base for asymmetric transformations

Carbohydrates constitute a class of inexpensive natural products of high chiral content [1]. They play central roles in the posttranslational biological selectivity [2]. O-Acyl-protected glycosylamines, particularly the 2,3,4,6-tetra-O-pivaloyl-D-galactopyranosylamine and its acetyl derivative are effective chiral auxiliaries in Strecker and Ugi syntheses of α-amino acids[3-5].Glycosylamines are valuable intermediates in the preparation of nucleosides and drugs[6-8]. Carbohydrate-derived auxiliaries utilize an efficient stereoselective potential in a number of nucleophilic addition reactions on prochiral imines.α-Amino acids, β-amino acids and their derivatives can be synthesized in few synthetic steps, with high enantiomeric purity. A variety of chiral heterocycles can readily be obtained from glycosyl imines by stereoselective transformations [9].The asymmetric Staudinger reaction utilizing 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosylamine as the chiral auxiliary in the synthesis of 2-azetidinones has been reported by us[10]. We now report compound 3 as a new chiral auxiliary Schiff base for β-lactam syntheses. © 2005 MDPI. All rights reserved.