Cholesteryl compound

Strong optical activity is exhibited, is known as the cholesteric state some workers regard this state as a special case of the nematic. The name arises from the fact that cholesteryl compounds form the majority of known examples. 

Cholesteryl compounds were the first materials that found application in thermography. 

When the mesogenic compounds are chiral (or when chiral molecules are added as dopants) chiral mesophases can be produced, characterized by helical ordering of the constituent molecules in the mesophase. The chiral nematic phase is also called cholesteric, taken from its first observation in a cholesteryl derivative more than one century ago. These chiral structures have reduced symmetry, which can lead to a variety of interesting physical properties such as thermocromism, ferroelectricity, and so on. 

A considerable number of compounds with alkoxy (aryloxy) and trialkylsiloxy ligands (including some embodying cholesteryl units)368 have been made in this way. 

Cholesteryl fluoroacetate was made in an attempt to discover whether a combination of fluoroacetic acid and some biologically important compound might give a product of increased toxicity. This compound, however, placed considerable limitations upon injection experiments owing to its low solubility in non-toxic solvents. It appeared, however, to be considerably less toxic than M.F.A. 

OT-CEC modified with different surface moieties (butylphenyl, cholesteryl, and biphenyl compounds)... 

Weichert also synthesized sterol esters of triiodinated biliary contrast agents [83], such as cholesteryl, pregnenolone and dehydroepandrosterone iopanoate (Fig. 13). Only the first compound accumulated in the liver. The reason probably was its resistance to hydrolysis. 

The history of liquid crystals started with the pioneer works of Reinitzer and Lehmann (the latter constructed a heating stage for his microscope) at the end of the nineteenth century. Reinitzer was studying cholesteryl benzoate and found that this compound has two different melting points and undergoes some unexpected color changes when it passes from one phase to another [1]. In fact, he was observing a chiral nematic liquid crystal. 

LCAT catalyzes the transfer of a preferentially unesterified fatty acid from the sn-2 position of phosphatidylcholine to the 3/i-hydroxy group of cholesterol, and thereby produces lysophosphatidylcholine and a cholesteryl ester [50]. Depending on the mutation in the LCAT gene, homozygous or compound heterozygous patients present with one of two clinical phenotypes, classical LCAT deficiency or fish-eye disease [58, 85]. Classical LCAT deficiency is caused by a broad spectrum of missense and non-sense mutations that interfere with the synthesis or secretion or affect the catalytic activity of LCAT [10]. Fish-eye disease is caused by a limited number of missense point mutations that alter the surface polarity, and thereby interfere with the binding of the enzyme to apoA-I containing lipoproteins [77]). 

The receptors can be recycled, whereas the lipoprotein remnants in the vesicle are transferred to lysosomes and degraded by lysosomal (hydrolytic) enzymes, releasing free cholesterol, amro acids, fatty acids, and phospholipids. These compounds can be reutilized by the cell. [Note Rare autosomal recessive deficiencies in the ability to hydrolyze lysosomal cholesteryl esters (Wolman disease), or to transport unesterified cholesterol out of the lyso some (Niemann-Pick disease, type C) have been identified.]... 

Liquid Crystals Liquid-crystal phases may occur between the solid and the liquid phase. Cholesteryl myristate, for example, exists in a liquid-crystal phase between 71 and 85°C [6]. The appearance of liquid-crystal phases depends on the molecular structure. Compounds with elongated structures that are fairly rigid in the central part of the molecule are likely candidates for liquid crystals. The homologous series of p-alkoxybenzylidene-p-n-butylanilines is just one example for compounds with liquid-crystal phases. An excellent introduction to liquid crystals and their properties has been written by Collings [6]. 

In 1946 Shoppee noted that the reaction of 3- -cholesteryl chloride with acetate ion proceeds entirely with retention of configuration (Equation 6.29). Substitutions on the analogous saturated compound proceed with the expected... 

A recently developed antihyperlipidemic is ezetimibe (Zetia, A.113) (Figure A.31). Ezetimibe inhibits the absorption of cholesterol across the intestinal wall. Like fibrates, ezetimibe is often prescribed with statins, although the effectiveness of ezetimibe has recently been called into question. A compound that may soon be approved for the treatment of high cholesterol is anacetrapib (A.114). Anacetrapib, a product of Merck, is currently in phase III trials. The compound inhibits cholesteryl ester transfer protein (CETP). The net effect of CETP inhibition is elevated HDL cholesterol and lower LDL cholesterol levels. 

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