Cholesteryl

The positional order of the molecules within the smectic layers disappears when the smectic B phase is heated to the smectic A phase. Likewise, the one-dimensional positional order of the smectic M phase is lost in the transition to the nematic phase. AH of the transitions given in this example are reversible upon heating and cooling they are therefore enantiotropic. When a given Hquid crystal phase can only be obtained by changing the temperature in one direction (ie, the mesophase occurs below the soHd to isotropic Hquid transition due to supercooling), then it is monotropic. An example of this is the smectic A phase of cholesteryl nonanoate [1182-66-7] (4), which occurs only if the chiral nematic phase is cooled (21). The transitions are aH reversible as long as crystals of the soHd phase do not form. 

Chloro-a,/3-unsaturated aldehydes condense with ammonium thiocyanate to give isothiazoles (76EGP122249). 2,3-Diphenylcyclopropenone reacts with iV-sulfinyl-cyclohexylamine in the presence of nickel tetracarbonyl to give the isothiazolin-3-one 1-oxide (197) (79SST(5)345). Cholesteryl acetate reacts with trithiazyl trichloride in pyridine to give the isothiazolo steroid (198) (77JCS(P1)916). 

Cholesteryl myristate [1989-52-2] M 597.0. Crystd from n-pentanol. Purified by column chromatography with MeOH and evaporated to dryness. Recrystd and finally, dried in vacuum over P2O5. [Malanik and Malat Anal Chim Acta 76 464 1975]. 

A) From Cholesieryl Acetate (Note 6).-—Five grams of cholesteryl acetate (Note 7) and o.r g. of platinum oxide are... 

Peanut oil, glycerol phos-phatides, cholesteryl esters etc. 

Note Flavonoids react with the reagent even at room temperature [1] mycotoxins, steroids, purines, pyrimidines, cardiac glycosides and lipids only react on heating [2, 4-6]. Zirconyl sulfate can be used to replace the zirconyl chloride in the reagent this is reported to result in an increase in the sensitivity to certain groups of substances (e.g. cholesteryl esters, triglycerides) [4]. 

The displacement of homoallylic tosylates follows an entirely different course with a strong tendency for the formation of cyclo steroids. Thus, when the 3/ -tosylate of a A -steroid (187) is treated with lithium aluminum deuteride, the product consists mainly of a 3l3-di-A -steroid (188) and a 6c-dj-3,5a-cyclo steroid (189). The incorporation of deuterium at the 3 -position in (188) indicates that this reaction proceeds via a 3,5-cyclo cholesteryl cation instead of the usual S, 2 type displacement sequence. This is further substantiated by the formation of the cyclo steroid (189) in which the deuterium at C-6 is probably in the p configuration. ... 

The method of choice for the preparation of cholesta-3,5-diene is treatment of cholesteryl tosylate with potassium /-butoxide in DMSO. The mesylate and chloride react similarly. 

A solution of 10 g (0.023 mole) of cholesteryl acetate (mp 112-114°) in ether (50 ml) is mixed with a solution containing 8.4 g (0.046 mole) of monoperphthalic acid (Chapter 17, Section II) in 250 ml of ether. The solution is maintained at reflux for 6 hours, following which the solvent is removed by distillation (steam bath). The residue is dried under vacuum and digested with 250 ml of dry chloroform. Filtration of the mixture gives 6.7 g of phthalic acid (87% recovery). The solvent is evaporated from the filtrate under reduced pressure and the residue is crystallized from 30 ml of methanol, giving 6.0 g (58% yield) of -cholesteryl oxide acetate. Recrystallization affords the pure product, mp 111-112°. Concentration of the filtrate yields 1.55 g (15% yield) of a-cholesteryl oxide acetate which has a mp of 101-103° after crystallization from ethanol. 

For the separation of amino acids, the applicability of this principle has been explored. For the separation of racemic phenylalanine, an amphiphilic amino acid derivative, 1-5-cholesteryl glutamate (14) has been used as a chiral co-surfactant in micelles of the nonionic surfactant Serdox NNP 10. Copper(II) ions are added for the formation of ternary complexes between phenylalanine and the amino acid cosurfactant. The basis for the separation is the difference in stability between the ternary complexes formed with d- or 1-phenylalanine, respectively. The basic principle of this process is shown in Fig. 5-17 [72]. 

HJ. Kisner, C.W. Brown, GJ. Kavamos, "Simultaneous Determination of Triglycerides, Phospholipids, and Cholesteryl Esters by Infrared Spectrometry", Anal. Chem. 1982 (54) 1479-1485. 

Protein that transfers lipids among lipoproteins, especially cholesteryl ester from HDL to VLDL in exchange for triglycerides. 

Enzyme that converts free cholesterol to cholesteryl ester on HDL. 

Plasma lipid transfer proteins, which include the cholesteryl-ester-transfer-protein (CETP previously known as lipid transfer protein I, LTP-I) and the phospholipid-transfer-protein (PLTP previously known as lipid transfer protein II, LTP-II) mediate the transfer of lipids (cholesteryl esters, triglycerides and phospholipids) between lipoproteins present in human plasma. These proteins significantly affect plasma lipoprotein concentration and composition. 

CETP mediates the exchange of cholesteryl esters and triglycerides between HDL and the proatherogenic,... 

Qiu X, Mistry A, Ammirati MJ et al (2007) Crystal structure of cholesteryl ester transfer protein reveals a long tunnel and four bound lipid molecules. Nat Struct Mol Biol 14 106-113... 

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