Abstract: An optically active compound having a .delta.-valerolactone ring which is a ferroelectric liquid crystal and is represented by the following general formula (I): ##STR1## wherein m is an integer of from 1 to 8, Z is a group represented by the following formula: ##STR2## in which each of l and k is a number of 1 or 2 and l and k satisfy the requirement of 2.ltoreq.(l+k).ltoreq.3,X stands for a direct bond, ##STR3## Y stands for ##STR4## and A.sub.1 and A.sub.2 independently stand for --H, --F or --Cl, ##STR5## R stands for ##STR6## in which n is an integer of from 1 to 18, and * indicates the asymmetric carbon atom.

Abstract: Disclosed is a mesomorphic compound having a .beta.-hydroxycarboxyl group as the chiral source, which is represented by the formula: ##STR1## wherein m and n are integers of from 1 to 18, X.sub.1 and X.sub.2 independently represent fluorine, chlorine or hydrogen, Y represents ##STR2## or --O--, Z represents a direct bond, ##STR3## --CH hd 2O-- or --OCH.sub.2 --, and * indicates the asymmetric carbon. The mesomorphic compound is valuable as a ferroelectric liquid crystal or an additive to a ferroelectric liquid crystal or to a compound showing the SmC phase and having no chiral group.

Abstract: Disclosed is an .alpha.-methylcinnamic acid ester derivative represented by the formula: ##STR1## wherein n is an integer of from 5 to 18, R.sub.1 represents an optically active group of the formula ##STR2## in which m is an integer of from 1 to 5 and *C represents an asymmetric carbon atom, and R.sub.2 represents ##STR3##The .alpha.-methylcinnamic acid ester derivative is valuable as a ferroelectric liquid crystal or an additive to a ferroelectric liquid crystal.