Optically active compounds of the following general formula (1) useful as chiral dopant, wherein n is an integer of 0 to 5, provided that when n is 0, A is a single bond (—) and that when n is 1 to 5, A is a single bond (—), —O—, —COO—, —Cy— or —Cy—COO— in which —Cy— is a trans-1,4-cyclohexylene group, each of X and Y is independently a hydrogen atom or a fluorine atom, B is a single bond (—), —COO—, —COO—Ph— or —Ph—COO— in which —Ph— is a 1,4-phenylene group, and C* is an asymmetric carbon. The chiral dopant of the present invention have a high helical twisting power of at least 9 and suitably have a feature that the helical pitch induced by them decreases in length with an increase in temperature so that they are advantageous for use in a nematic liquid crystal composition.