The invention relates to polysubstituted butanoic acids, esters and derivatives thereof which have been found to be useful as herbicides in the control of undesirable mono- and di-cotyledonous plants. The active compounds have the formula:
wherein R, is OH, OR 4 , NR 5 R 6 or OM; R 2 and R 3 each represent a member selected from the group consisting
pyridyl and thienyl; R 4 is alkyl C 1 -C 8 , monohaloalkyl C 1 -C 4 , monohaloalkynyl C 3 -C 4 , monohaloalkenyl C 3 -C 4 , alkoxy C 1 -C 4 alkyl C 1 -C 4 or hydroxyalkynyl C 2 -C 4 ; R 5 and R 6 each independently represent members selected from the group consisting of H and alkyl C 1 -C 2 ; M is an alkali metal, ammonium, C 1 -C 8 mono or di-alkylammonium or hydroxyethylammonium; and X and Y each independently represent members selected from the group consisting of hydrogen, halogen, alkyl C 1 -C 4 ; alkoxy C 1 -C 4 , OCF 3 , OCHF 2 , CF 3 , CN, COOH, NO2, OH, SCH 3 , NR 7 R 8 , CH 3 SO 2 , and when X and Y are taken together they may represent -OCH 2 O- jointed to adjacent positions of the benzene ring and R 7 and R 8 are each hydrogen or alkyl (C 1 -C 2 ). Compounds of formula (I) exist in threo and erythro stereoisomeric forms, and in general the threo isomers (many of which are novel compounds) are the more active herbicidal agents. Accordingly it is generally preferred to employ the threo stereoisomers and threo-erythro mixtures.