Azlactone compound and method for preparation thereof

A method of making a compound represented by formula (II):

• wherein:
• M is a hydrogen atom, sodium, potassium, or lithium;
• P is a hydrogen atom, an alkyl group, an alkenyl group, an aryl group optionally having one or more substituents, an aralkyl group optionally having one or more substituents, or a haloalkyl group;
• and
• a wavy line indicates a cis form, a trans form, or a mixture thereof for the carbon-carbon double bond to which it is attached,
• said method comprising:
• (1) hydrolyzing a compound represented by formula (I), or a salt thereof:
• wherein:
• R1 and R2 are the same or different and each is an alkyl group, or R1 and R2 may be bonded together to form an aliphatic heterocycle together with the adjacent nitrogen atom;
• and
• P and a wavy line are as defined above,
• in the presence of alkali metal hydroxide, to obtain said compound of formula (II).