1,3-Dipolar Cycloadditions of D-Erythrose- and D-Threose-Derived Alkenes with Nitrones

Abstract

The new chiral terminal alkenes derived from cyclic acetals of D-erythrose 1-3 and D-threose 5, 6 were prepared. The alkenes 1, 2 and 5 react with chiral nitrones to afford the corresponding diastereomeric isoxazolidines 19-21. The stereoselectivity was dependent on the steric hindrance of the nitrone. In all cases the cycloadditions are endo-selective. The major products were found to have the C-3/C-4 erythro- and C-3/C-3a cis-configuration. Its formation can be rationalized by a less hindered endo-attack of the (Z)-nitrone in an antiperiplanar manner with respect to the largest group of the cyclic acetal.