The synthesis of cholest-5-ene-3beta-carboxylates and a comparison of their mesomorphic behaviour with isomeric cholesterol esters with a reversed ester linkage

The syntheses of seven esters of cholest-5-ene-3beta-carboxylic acid are reported and the melting points, transition temperatures and mesophase morphologies of the esters are compared with those of the isomeric 3beta-cholesterol compounds which have the ester link reversed. For the examples reported, the cholest-5-ene-3beta-carboxlates always have significantly lower melting points, but the differences in clearing temperatures for the two series of esters are usually much less. Several of the new compounds give an increased chiral nematic phase range and an intense selective reflection of light. They therefore represent a novel type of chiral nematic material for use in thermochromic applications.