Optically active N-acyl aziridine 2-imides or 2-carboxylates rearrange to oxazoline-4-imides or 4-carboxylates with high regio and stereo control. This ring expansion followed by mild hydrolisis allows the synthesis of enantiomerically pure β-hydroxy α-aminoacid precursors.
The microwave-assisted ring expansion of N-acetyl 3'-unsubstituted aziridine-2-imides and N-acetyl 3'-unsubstituted aziridine 2-esters to oxazolines is reported. The regioselectivities of the rearrangements depend upon the reaction conditions, such as the Lewis acid selected and the solvent. (C) 2001 Elsevier Science Ltd. All rights reserved.