enantiomerically pure aziridinylmethyl azide is described that can be transformed to the corresponding triazole by a copper-catalysed [3+2] alkyne cycloaddition reaction. The transformation of these intermediates into triazolylalanine-type derivatives by aziridine ring-opening reactions is also described. copper catalyst - 1,2,3-triazole - aziridine - cycloaddition - ring-opening reaction - alanine