Asymmetric synthesis of 1-azaspiro[4.5]decanes via intramolecular dipolar cycloaddition of nitrones containing the bornane-10,2-sultam chiral auxiliary

The intramolecular 1,3-dipolar cycloaddition of a cyclic nitrone, prepared by an asymmetric electrophilic enolate hydroxyamination using the (2R)-bornane-10,2-sultam chiral auxiliary, proceeds to give bridged and fused cycloadducts with total diastereocontrol. Reduction of the fused isoxazolidine provides a 1-azaspiro[4.5]-decane as a potential intermediate in the asymmetric synthesis of the cylindricine alkaloids. (C) 2000 Elsevier Science Ltd. All rights reserved.