The author prepared CH3(CH2)3CHCH2CH2CO _??_ from CH2=CH (CH2)5COOH. The raw material is obtained from the oil after electrolytic oxidation of CH3OOC(CH2)7COOK and contains CH3(CH2)6COOH. Treatment of the mixture of two acids with conc. H2SO4 results in a shift in the double bond of CH2=CH(CH2)5COOH until it reaches beta and gamma position, and this is followed by cyclization to the lactone. It posesses coconut like odor and is one of useful flavoring materials. At the same time, CH3(CH2)6COOH is recovered in this procedure and two components are separated effectively.