A NEW ROUTE TO 3,5-DISUBSTITUTED ISOXAZOLIDINES VIA THE IODOCYCLIZATION OF HOMOALLYLIC HYDROXYLAMINES

N,N-Dialkyl-O-trialkylsilyl homoallylic hydroxylamines reacted with iodine, N-iodosuccinimide, or iodine chloride to give 3,5-disubstituted isoxazolidines in good yield. The relative configuration that was generated at C3 and C5 was controlled by the nature of the nitrogen substituent of the parent hydroxylamine: the presence of a primary alkyl group favored the formation of a cis-isoxazolidine, whereas the presence of a tert-butyl group favored the formation of a trans-isoxazolidine. The effects that the N- and O-substituents and the nature of the iodinating agent exerted on the stereoselectivity of the cyclization were examined. The synthesis of enantiomerically pure isoxazolidines from hydroxylamines carrying a chiral N-mannofuranosyl group is described.