We have prepared and studied four binary systems by doping a nonmesogenic optically active compound, namely 6-methoxy-2',4"-dibenzoylerythromycin, in various mesogenic compounds, namely 4-(4"-n-alkoxybenzoyloxy)phenylazo-4'-isoamyloxybenzenes (C-8, C-10) and 4-(4'-n-alkoxybenzoyloxy)benzylidine-4'-isoamyloxy anilines (C-8, C-10). The central linkages and terminal groups of the mesogenic compounds have been varied systematically, and the effect of these variations have been evaluated on the liquid crystalline properties of the mixtures. A wide variety of mixed mesomorphic properties exhibiting chiral nematic and chiral smectic C mesophases were observed in these binary systems. The properties of these systems are discussed on the basis of phase diagrams.