PURPOSE: To obtain a novel fluorolactone which is useful as a synthetic intermediate for medicines or agrochemicals.

CONSTITUTION: This fluorolactone is represented by formula I or II (R1-R3 are each an alkyl, an aryl, H), for example, 5-(1'-fluoroethyl)-5-phenyl-2- oxotetrahydrofuran. A compound of formula I or II is obtained by reaction of an alkenylcarboxylic acid of formula III such as 4-phenyl-4-hexenoic acid with an N-fluoropyridinum salt of formula IV (R4-R8 are each chlorine; X- is a conjugated base of a Bronsted acid) such as N-fluoropentachloropyridinium trifluoromethanesulfonate.