Stereoselective reactions of ephedrine-derived alkylidene morpholinones for the synthesis of (+)-Epilupinine, (+)-Epitashiromine and functionalized quaternary stereocenters

Abstract

The stereoselective 1,3-dipolar cycloaddition reaction of cyclic nitrones with ephedrine-derived alkylidene morpholinones provided the corresponding spiro isoxazolidines which were converted to naturally occurring indolizidine and quinolizidine alkaloids. A detailed investigation of the cycloaddition reaction and the conversion of the isoxazolidine intermediates to (+)-epilupinine and (+)-epitashiromine is described in Chapter 2. In a separate study, haloalkylidene morpholinones were used as substrates for metal-catalyzed cross-coupling reactions to provide diastereomerically pure, substituted alkylidene morpholinones. These were subjected to a stereoselective Prins reaction to provide diastereomerically pure spirodioxolane intermediates which were converted to β-hydroxy carboxylic acids with a quaternary stereocenter at the α carbon. This methodology is described in Chapter 3. Investigations of alkylidene dioxolanones, as potential substitutes for the ephedrine-derived alkylidene morpholinones employed in Chapters 2 and 3, are described in Chapter 4.