Whereas treatment of the allylic mesylates of N-protected 2-alkyl-4-amino-(E)-2-alken-1-ols with sodium hydride in DMF yields exclusively the corresponding 2,3-trans-2-alkenyl-3-alkylaziridines, exposure of the methyl carbonates of N-protected 2-alkyl-4-amino-(E)-2-alken-1-ols to Pd(PPh3)(4) (5-20 mol%) in THF or 1,4-dioxane affords predominantly the corresponding 2,3-cis-2-alkenyl-3-alkylaziridines. These reactions can be used to synthesize either of two diastereomers from single common intermediates. (C) 1999 Elsevier Science Ltd. All rights reserved.