title: On the regio- and stereoselective synthesis of aminocyclitols from cyclitol epoxides: the effect of Li as a chelating agent.
abstract: Experimental and theoretical studies on the influence of Li ions on the regio- and the stereoselectivity of the reaction of cyclitol epoxides with nitrogen nucleophiles have been carried out. Model studies with NaN3 as a nucleophile in the absence of Li ions predict a mixture of C1 and C2 regioadducts. The inclusion of two Li ions as a chelating agent favours the operation of a low populated "all-axial" conformation leading ultimately to the C1 adducts. In all cases, the results can be rationalised by geometric and energetic considerations of the corresponding transition states. Predictions of the theoretical calculations are in good agreement with the experimental results using primary and secondary amines as nucleophiles, and thus confirm the validity of this study.
authors.affiliation: Universidad de Barcelona, Facultad de Farmacia, Unidad de Química Farmacéutica, 08028 Barcelona, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Serrano
authors.forename: Amadeu
authors.initials: A
authors.lastname: Llebaria
authors.forename: Jordi
authors.initials: J
authors.lastname: Vázquez
authors.forename: Joan
authors.initials: J
authors.lastname: de Pablo
authors.forename: Josep M
authors.initials: JM
authors.lastname: Anglada
authors.forename: Antonio
authors.initials: A
authors.lastname: Delgado
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D013237:Stereoisomerism
chemical_list: D002614:Chelating Agents; D004852:Epoxy Compounds; D008094:Lithium