an oxazolinone derivative compound , represented by the general formula i , shows superior herbicidal activity against , especially , dicotyledonous vegetables . it is effective upon applying both before and after the sprouting of vegetables . it is prepared by condensating an α - amino acid represented by the general formula ii with an acid chloride represented by the general formula iii , to give an acyl α - amino acid represented by the following formula iv : reacting the acyl α - amino acid with acetic anhydride ; and dehydrating the resulting adduct : ## str1 ## wherein , r represents a lower alkyl group or a phenyl group containing halogen , lower alkyl or trifluoromethyl group ; x represents halogen atom , carbomethoxy group , nitro group , or halogen or trifluoromethyl - substituted phenoxy group , being the same or different from one another ; a represents nitrogen or carbon atom ; and n is an integer of 1 to 3 .