Synthesis of methyl-α-d-glucopyranoside-based azacrown ethers and their application in enantioselective reactions

New chiral monoaza-15-crown-5 compounds anellated to methyl-4,6- O -(1-naphthyl)methylene-α- d -glucopyranoside ( 2a – 2b ), to methyl-4,6- O -isopropylidene-α- d -glucopyranoside ( 3a – 3b ) and to methyl-α- d -glucopyranoside ( 4a – 4b ) have been synthesized. Several representatives of these crown ethers showed significant asymmetric induction as chiral phase transfer catalysts, among them 2a proved to be the most efficient one inducing 90% ee in the Michael addition of 2-nitropropane to chalcone, 48% ee in the Darzens condensation of phenacyl-chloride with benzaldehyde and 89% ee in the epoxidation of chalcone with tert -butyl hydroperoxide. The catalytic results were compared with those obtained earlier with macrocycles 1a – 1b incorporating a 4,6- O - benzylidene protecting moiety. It occurred that the enantioselectivity is influenced to a great extent by the substituents on the C(4) and C(6) atoms of the monosaccharide. Lower enantioselectivities were obtained in the reactions of the chalcone analogues in the presence of catalyst 2a than in the case of the proper chalcone.