摘要:
An optically active compound having the formula: ##STR1## wherein each of Z and Z' is a single bond, --COO--, --OCO--, --CH.sub.2 CH.sub.2 --, --OCH.sub.2 -- or --CH.sub.2 O--, R is an alkyl group having from 1 to 12 carbon atoms, an alkoxyl group having from 1 to 12 carbon atoms, a cyano group or a halogen atom, each of rings A and B is a 1,4-di-substituted phenylene group or a trans-1,4-di-substituted cyclohexylene group, n is 0 or 1, X is ##STR2## wherein * indicates an optical center, and R' is an alkyl group having from 2 to 12 carbon atoms or ##STR3## where R" is a hydrogen atom, an alkyl or alkoxy group having from 1 to 12 carbon atoms, provided that when X is ##STR4## R is the alkyl group or the alkoxy group.