Optically active compounds having the following formulae (1), (2) or (3) ##STR1## wherein R and R' are C.sub.1-20 alkyl groups; X and Y.sub.1 are --, O, S, or divalent groups such as COO, OOC and OCOO; m is 0 or 1; n is 0 to 5; A.sub.2 is a cyclic group, such as p,p'-biphenylene, 2,6-naphthylene, 2,5-pyrimidinylene-1,4-phenylene, A.sub.1 --Y.sub.2 -pyridylene or A.sub.4 --Y.sub.2 --A.sub.5 ; Y.sub.2 is CH.sub.2 CH.sub.2 or C.tbd.C; A.sub.3 is 2,6-naphthylene, A.sub.1 --Y.sub.2 -pyridylene or A.sub.6 --CH.sub.2 CH.sub.2 --A.sub.7 ; and A.sub.1, A.sub.4, A.sub.5, A.sub.6 and A.sub.7 are cyclic groups, such as 1,4-phenylene and/or 4,4'-biphenylene.