To reduce the bulky steric hindrance, improve the reactivity of diosgenin and cholesterol, and obtain mesophase of their derivatives, the commercially available cholesterol and diosgenin were allowed to be structurally modified. Four new chiral LC intermediate compounds (c similar to f) and the corresponding monomers (M-1-M-4) with different longer spacer were synthesized. The chemical structures, optical texture, thermal behavior and mesophase structure of all the mesogenic compounds obtained in this study were characterized by FT-IR, H-1-NMR, polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction measurements. The experimental results showed that the intermediate compounds containing diosgenyl groups c and d only showed a mesophase and exhibited fan-shaped texture of a smectic A (S-A) phase, while the compounds containing terminal cholesteryl groups e and f showed two mesophases and exhibited fan-shaped texture of a S-A phase, and oily streak texture and focal conic texture of cholesteric phase, respectively. The four chiral monomers M-1-M-4 all revealed cholesteric oily streak texture and focal conic texture. In addition, the melting temperature (T-m) and isotropic temperature (T-i) of the mesogenic compounds decreased with increasing the flexible spacer length. Compared with the intermediate compounds or monomers based on cholesterol, the compounds or monomers based on diosgenin showed higher T-m and T-i.