PURPOSE: To obtain the subject new compound, having excellent carcinostatic action and low toxicity and useful as a carcinostatic agent.

CONSTITUTION: A compound expressed by formula I (X is H, halogen, 1-5C lower alkyl, etc.; R1 and R2 are H or 1-5C lower alkyl), e.g. ethyl 6-(4- chlorophenyl)-3-hydroxy-6-oxo-2,4-hexadienecarboxylate. The 3-hydroxy derivative in the compound is obtained by reacting a 3-alkoxycarbonyl-2- oxopropylidenetriphenylphosphorane expressed by formula II with a glyoxal expressed by the formula R-COCHO (R is phenyl, halogen, etc.) in an organic solvent such as THF. The compound expressed by formula II is preferably reacted with the glyoxal in about equimolar amounts.