Novel antiferroelectric liquid crystals having phenylalkanoate and phenylalkenoate moieties were synthesized and their mesomorphic properties were studied. 4-[2-{1-(Trifluoromethyl)heptyloxycarbonyl}ethyl]phenyl 4’-decyloxybiphenyl-4-carboxylate 1b exhibited the chiral smectic C-A phase at a temperature below the chiral smectic C phase. Biphenyl-cinnamate derivatives of the three-ring system exhibited a stable mesomorphic phase and enantiotropic smectic C-A phase, with the carbon-carbon double bond acting as a mesogenic core.