Synthesis of D-erythrose and D-threose derived nitrones and cycloadditions to styrene

The new nitrones derived from cyclic acetals of D-erythrose (2a-c) and D-threose (8) react with styrene to afford the corresponding 3,5-disubstituted diastereomeric isoxazolidines 3-6 and 9-12. The stereoselectivity was dependent on the steric hindrance of the nitrone. The major products 3a-c (55-58 %) and 9 (73 %) were found to have the C-3/C-4' erythro and C-3/C-5 cis relative configuration by X-ray analysis. Its formation can be rationalized by less hindered endo attack of the Z-nitrone in an antiperiplanar manner with respect to the largest group of the cyclic acetal. (C) 1999 Elsevier Science Ltd. All rights reserved.