Substituted lactic acid derivatives having an N-organic radical in the .beta.-position, of the formula I ##STR1## where substituents R to R.sup.5, X and Y have the meanings mentioned in the description and N is one of the radicals: a) --N.sub.3, --NC, --NCS or --NCO b) ##STR2## where R.sup.14 and R.sup.15 have the meanings described in the description c) ##STR3## in which R.sup.16 is hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl or unsubstituted or substituted phenyl; and B is a group ##STR4## OR.sup.19 or --NR.sup.14 R.sup.15, where R.sup.14, R.sup.15, R.sup.17 and R.sup.19 have the meanings described in the description, or ##STR5## where R.sup.14 and R.sup.15.sub.1, have the abovementioned meanings; or ##STR6## where R.sup.20 and R.sup.21, which can be identical or different, are: hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl or phenyl, where the organic radicals can in each case be substituted; or R.sup.20 and R.sup.21 together form an unsubstituted or substituted C.sub.4 -C.sub.7 -alkylene chain which is closed to give a ring or together form an unsubstituted or substituted C.sub.3 -C.sub.6 -alkylene chain which is closed to give a ring and has a heteroatom selected from the group consisting of oxygen, sulfur and nitrogen are described.