Optically active compounds, liquid crystal compositions comprising said compounds and liquid crystal optical modulators using said compositions

Optically active compounds represented by the general formula ##STR327## wherein R.sub.1 is an alkyl group, an alkenyl group or an alkynyl group each of 3-14 carbon atoms;

• R.sub.2 is an alkyl group of 1-10 carbon atoms, an alkenyl group of 2-10 carbon atoms or an alkynyl group of 2-10 carbon atoms;
• ##STR328## Q.sub.1 is a single bond, a (thio)ether group, a carboxylic acid ester group, a carbonyl group or a carbonyldioxy group;
• Q.sub.2 and Q.sub.3 are independently, a (thio)ether group, a carboxylic acid ester group, a carbonyl group, a carbonyldioxy group or a methyleneoxy group;
• M is ##STR329## (X and Y are independently a single bond, a carboxylic acid ester group, a methylenoxy group or an ethylene group, and ##STR330## are independently a six-membered ring-1,4-diyl group which may contain 1-2 oxygen or nitrogen atoms as ring-forming atoms);
• the carbon atoms with the asterisk (*) denote asymmetric carbon atoms.