Non-decarboxylative 1,3-dipolar cycloadditions of imines of α-amino acids as a route to proline derivatives

Article abstract of DOI:10.1016/S0040-4020(01)81114-5

α-Amino acids react with aryl aldehydes in the presence of N-substituted maleimides to yield stereospecific cycloadducts (3a,b) and with dimethyl fumarate to give isomeric mixtures of (4a-i) and (5a-i). The relatively low yield in the case of dimethyl fumarate is presumably due to the steric interaction between the dipolaraphile and the substituents at both ends of the dipole.