trans-Acetonide Controlled endo-Selective Intramolecular Nitrone−Alkene Cycloaddition of Hept-6-enoses:  A Facile Entry to Calystegines, Tropanes, and Hydroxylated Aminocycloheptanes

High-yielding endo-selective intramolecular nitrone−alkene cycloaddition (INAC) reactions of hept-6-enoses controlled by a trans-acetonide to give bridged bicyclo[4.2.1]isoxazolidines exclusively are realized for the first time. The cycloadducts were readily transformed into calystegine, tropane, and hydroxylated aminocycloheptane frameworks.