A new optically active (R)-3-ethylmercapto-2-methylpropionic acid has been synthesized usingD(-)—2,10-camphorsultam as a chiral auxiliary. The optical purity of the acid obtained was greater than 98 per cent. Its derivatives, (R)-4-(3-ethylmercapto-2-methylpropionyl)phenyl 4′-alkoxybiphenyl-4-carboxylates (EMMPPmBC;m= 7–16), have been prepared for the investigation of liquid crystalline properties as a function of peripheral alkyl chain length. Optical studies showed that all members exhibited an antiferroelectric S*cAphase. The results also indicate that a lengthened alkyl chain length is favoured for ScA* phase formation.