reacted with anhydrous ethanol to yield an optically active monoethyl ester of u03b1 acetoxydibasic acid as represented by the following reaction formula see tetrahedron 41 no 13 2751 2758 1985 str11 the obtained optically active u03b2 hydroxycarboxylic acid is electrolytically reacted with the optically active monoethyl ester of u03b1 acetoxydibasic acid to kolbe electrolysis as indicated by the following reaction formula str12 and the obtained product is cyclized in the presence of p toluene sulfonic acid to obtain the above mentioned valerolactone derivative as shown by the following reaction formula str13 the substance represented by general formula 1 can be synthesized through the following routes a where y is general formula 1 is co 2 the synthesis route is expressed as follows str14 b where y in general formula 1 is o the synthesis route is expressed as follows str15 c where y in general formula 1 is ch 2 o the synthesis route is expressed as follows str16 since the optically active substance of the present invention does not possess an azomethine bond inherently possessed by the conventional ferroelectric liquid crystal substances the substance of the present invention has a greatly improved chemical stability such as the hydrolysis resistance and an improved light stability compared to the conventional cinnamic acid type compounds therefore the substance of the present invention has excellent characteristics required for a display material the optically active substance of the present invention does not always show the chiral smectic c phase hereinafter referred to as 34 sm c phase 34 alone but the optically active substance of the present invention is characterized in that when the substance is mixed with other liquid crystal substance having the sm c phase or other ferroelectric liquid crystal.