PURPOSE: To obtain the titled compound useful as an anti-inflammatory agent, industrially and advantageously, by the reaction of a novel propionic acid ester derivative with sulfur and a secondary amine, and the subsequent hydrolysis and then the cyclization of the hydrolysis product in the presence of a condensing agent.

CONSTITUTION: A novel compound of formula I (Z is O or S; R1 is lower alkyl) is reacted with sulfur and a secondary amine of formula II (R2 and R3 are lower alkyls or a heterocyclic ring with the N adjacent), for example, under the usual Willgerodt-Kindler reaction conditions, to prepare the compound of formula III, which is hydrolyzed by the conventional method to give a dicarboxylic acid of formula IV. The resulting compound is cyclized in the presence of a condensing agent, e.g. polyphosphoric acid, which is applied to the intramolcular acylation, to give a propionic acid derivative of formula V. This reaction is suitable for an industrial process because of high yield and less reaction stages than the conventional ones and no dangerous reaction.