To obtain a new twin compound useful as a material for adjusting the spiral pitches of liquid crystals, etc., by reacting a diepoxide with trimethylaluminum, etc., and subsequently esterifying the reaction product with a 4-(5-alkylpyrimidin-2-yl) benzoic acid.

A new twin compound of formula I [(a) is 0, 1; (b) is 3-15; (c) is 0, 1; (d) is 0, 1; (m) is an integer of 1-18]. The compound is useful as a material for adjusting the spiral pitches of liquid crystals, especially ferroelectric liquid crystals expressing cholesteric phases and chiral smectic C phases, and is added to liquid crystal compositions, etc. The compound is obtained by reacting a diepoxide of formula II with trimethylaluminum or lithium aluminum hydride and subsequently esterifying the obtained diol of formula III with a 4-(5-alkylpyrimidin-2-yl)benzoic acid having a 1-18C alkyl group.