Intramolecular 1,3-dipolar nitrone cycloaddition onto an enantiomerically pure ketene dithioacetal dioxide using a three-carbon tether gave the corresponding 5,5-disubstituted isoxazolidine as a single diastereomer in good yield. This reaction has been used as the key step in an asymmetric synthesis of the naturally occurring antibiotic, (-)-cispentacin. An asymmetric synthesis-of 4-amino-pyrrolidine-3-carboxylic acid has also been carried out using the intramolecular nitrone cycloaddition as the stereocontrolling step.
- DIELS-ALDER REACTIONS
- PHYSICOCHEMICAL PROPERTIES