Abstract: The invention concerns novel compounds of the formula I ##STR1## wherein: R.sup.1 is selected from alkyl, alkenyl, alkynyl, cycloalkyl benzyl and substituted benzyl;A is selected from hydrogen, halogen, nitro, alkyl, alkoxy, alkylthio, alkenylthio, alkynylthio, cycloalkoxy, cycloalkylthio, sulfamoyl, N-(C.sub.1 to C.sub.6 alkyl)sulfamoyl, N,N-di(C.sub.1 to C.sub.6 alkyl)sulfamoyl, benzylthio and substituted benzylthio;R.sup.2 is selected from hydrogen, alkyl, alkenyl, alkynyl, substituted alkyl, acyl, alkylsulfonyl, benzenesulfonyl, substituted benzenesulfonyl, and an inorganic or organic cation;R.sup.3 is selected from alkyl, alkenyl, alkynyl, substituted alkyl, haloalkenyl and haloalkynyl; andR.sup.4 is selected from alkyl, fluoroalkyl, alkenyl, alkynyl and phenyl.