N-Substituted C-diethoxyphosphorylated nitrones as useful synthons for the synthesis of α-aminophosphonates

A convenient method for the synthesis of N-substituted C-phosphorylated nitrones 2 from hydroxymethylphosphonates via successive Swern oxidation and treatment with respective hydroxylamines is reported for the first time. Moderate (20%) to excellent (up to 90%) diastereoselectivities in cycloadditions of nitrone 2a and terminal alkenes were observed with trans C5-substituted isoxazolidines predominating. In ZnCl2-catalysed cycloadditions, mixtures enriched in cis diastereoisomers were produced.