Abstract: New derivatives of N.sup.3 -D-trans-2,3-epoxysuccinamoyl-L-2,3-diaminopropanoic acid of formula (1) ##STR1## wherein R.sub.1 is hydrogen; or R.sub.1 is the residue of an amino acid selected from L-valine, L-norvaline, L-leucine, L-isoleucine, L-norleucine, L-methionine, L-lysine, L-2-aminobutanoic acid, L-aspartic acid and L-glutamic acid;or R.sub.1 is the residue of a dipeptide selected from L-norvalyl-L-norvaline, L-lysyl-L-norvaline, L-methionyl-L-norvaline, L-glutamyl-L-norvaline, L-norvalyl-L-methionine, L-methionyl-L-methionine, L-leucyl-L-norvaline, L-norleucyl-L-norvaline, L-valyl-L-norvaline, L-glutamyl-L-leucine, L-asparginyl-L-norvaline and L-leucyl-L-leucine;wherein R.sub.2 is hydroxyl;or R.sub.2 is the residue of an amino acid selected from L-alanine, L-methionine, L-valine, L-norvaline, L-leucine, L-isoleucine, L-norleucine and L-2-aminobutanoic acid; with the provisos that when R.sub.1 is hydrogen then R.sub.2 is an amino acid residue and that when R.sub.