To make it possible to obtain the subject compound useful for synthesizing natural products with good yield, by reacting (R)-β-trichloromethyl-β- propiolactone with a Grignard reagent or a lithium reagent.

(A) (R)-β-Trichloromethyl-β-propiolactone of formula I is reacted with (B) a Grignard reagent such as phenylmagnesium bromide, phenylmagnesium chloride or phenethylmagnesium bromide or a lithium reagent such as phenyl-lithium in (C) a solvent, e.g. diethyl ether, dimethoxyethane or tetrahydrofuran at -78 to -50°C reactional temperature to afford a compound formula II [R1 is a group of the formula Ph(CH2)n (Ph is phenyl; (n) is 0-2)].