Thermal transitions and structural properties of synthetic cholesterol alkyl and alkenyl ethers: analogues of biological cholesterol esters.

Nine even-numbered saturated (C4 to C20) and two unsaturated (C18:1, C18:2) cholesterol alkyl ethers were studied by differential scanning calorimetry, polarizing microscopy, and X-ray powder diffraction. Seven of the nine saturated ethers examined melt into stable liquid crystal mesophases. Mesophase transition temperatures vary over a much narrower range than in cholesterol esters and are lower than those of corresponding esters. Polarizing microscopy and X-ray diffraction show structural similarities between cholesterol ethers and esters. Since cholesterol ethers behave similarly thermotropically to cholesterol esters, they may serve as suitable nonmetabolizable analogues for cholesterol esters in biological systems.