Manufacture of aziridinocarboxylic acid esters

An improved process for the manufacture of aziridinocarboxylic acid esters of the general formula ##STR6## where A is hydrogen, methyl or the nth part of the group (--COO).sub.n R.sup.2, B is hydrogen or methyl, R.sup.1 is hydrogen or alkyl of 1 to 5 carbon atoms and R.sup.2 is the n-valent radical of an alcohol of at least 2 carbon atoms which contains at least n hydroxyl groups, and n is an integer not less than 2, by trans-esterification of compounds of the general formula (I), where R.sup.2 is a radical of methanol, ethanol or propanol, with an alcohol of at least 2 carbon atoms and containing at least n hydroxyl groups, in the presence of a basic trans-esterification catalyst, and removal of the resulting methanol, ethanol or propanol from the esterification equilibrium by distillation, wherein the improvement comprises using magnesium oxide or calcium oxide as the trans-esterification catalyst.