Cholesterol dehydrated

D-Mevalonic acid is the fundamental intermediate in the biosynthesis of the terpenoids and steroids, together classed as poly-isoprenoids. The biogenetic isoprene unit is isopentenyl pyrophosphate which arises by enzymic decarboxylation-dehydration of mevalonic acid pyrophosphate. D-Mevalonic acid is almost quantitatively incorporated into cholesterol synthesized by rat liver homogenates. 

Dehydrated cholesterol Apply sample solution then place TLC plate in an iodine vapor chamber, blow off excess iodine. Di- and trimeric components are produced. [54]... 

Sorm" " found that when cholesterol acetate (67) is oxidized by chromic acid in acetic acid-water at 55°, crystalline keto seco-acid (69) is obtained in 25-30 % yield from the mother liquors after removal of successive crops of 7-ketocholesterol acetate (68). Reaction of keto acid (69) with benzoyl chloride in pyridine gives a dehydration product, shown" to be the )5-lactone... 

Earlier work by Nancy Bucher showed an ATP requirement for cholesterol biosynthesis. The involvement of phosphorylated intermediates was established by Comforth, Popjak, and their associates in the early 1960s with the discovery of kinases which successively phosphorylated MVA to MVA-P and MVA-P to MVA-PP. MVA-PP was decar-boxylated and dehydrated to give the biological C5 isoprene unit, isopentenyl pyrophosphate. This undergoes successive head-to-tail condensations to give the linear 15C terpenoid, famesyl pyrophosphate. 

Abbreviations. HA, hemagglutinin DRV, dehydration-rehydration vesicles PC, phosphatidylcholine DOPE, dioleoyl phosphatidylcholine DOTAP, l,2-dioleyloxy-3-(trimethylamonium propane) BisHOP,, 2-bis (hexadecylcycloxy)-3-trimethylamino propane DC-CHOL, 3p(V,V,-dimethylami-noethane)-carbamyl cholesterol (DC-CHOL) DOTMA, V-[l-(2,3-dioleyloxy) propyl]-iV,V,V-triethylammonium PG, phosphatidyl glycerol PS, phosphatidylserine SA, stearylamine DODAP, l,2-dioleyloxy-3-(dimethylamonium propane). 

The effect of additives betrays the intricacy of the balance of rate effects even more. The addition of cholesterol to catalytic bilayers has been found to be beneficial for the Kemp eleminiation but to inhibit the decarboxylation of 6-NBIC. In general, the effects of additives on the decarboxylation of 6-NBIC appear to subtly depend on the structure of the hydrophobic tail and hydrophilic headgroup of additives. Similarly subtle effects were found for the Kemp elimination and nucleophilic attack by Br and water on aromatic alkylsulfonates depending on the choice of additive, hydrogen bonding effects, reactivity of partially dehydrated OH , and local water concentrations all played a role and vesicular catalysis could be increased or decreased. 

Z-17(20)-Dehydrocholesterol (231) has been prepared from pregnenolone by two independent routes. Dehydration of a mixture of 20a- and 20/3-hydroxy-cholesterol gave the required compound (231) along with the previously prepared... 

The structure proof for cholesterol paralleled that for two other important steroids, the so-called bile acids, cholic and desoxycholic acid, which function to help solubilize fats in the intestinal tract. Proof that cholesterol and the bile acids have the same general ring system was achieved by dehydration and reduction of cholesterol to two different hydrocarbons, 5a-cholestane and 5/3-cholestane (coprostane), which differ only in the stereochemistry of the junction between rings A and B ... 

A D20/lipid ratio of 2 1 (v w) led to easily handled samples and consistent spectroscopic results. Typically, 10 mg of specifically deuterated phospholipid and 20wl D2O were added to a culture tube, which was then sealed and incubated at 55°C for at least 1 hr, with periodic agitation to ensure complete dispersal and hydration. Similar procedures were followed for cholesterol and Gramicidin D-containing samples. Samples were placed between two AgCl windows, and sealed with a 6 pM, spacer. The assembly was wrapped with Teflon tape, as a further seal against dehydration, and inserted into a Harrick cell. Temperature was controlled to + 0.1 C with a Haake circulating water bath and monitored with a thermocouple placed as close as feasible to the point where the IR radiation was focused. 

Cholesterol has an alcohol group. One could also dehydrate cholesterol (removing one water molecule by heating). Show the structure you would expect from the dehydration of cholesterol. 

In 1974, Homberg (1974) reported that the action of bleaching earth on cholesterol in solutions of both synthetic triacylglycerol (TAG) and hexane caused the formation of the dehydration product cholesta-3,5-diene. Subsequently it was reported that bleaching of butterfat resulted in the formation of cholesta-3,5-diene (Roderbourg and Kuzdzal-Savoie, 1979) and the authors proposed that the detection of this artefact could be used to identify refined butterfat. In a review article (Kochhar, 1983), it was reported that several other authors had identified steradienes in bleached vegetable oils and proposed that the detection of these could be used to identify refined oils or mixtures of refined and unrefined oil. 

Oxidation of steroid S,7-dienes. The main product (about 60% yield) of the oxidation of A -cholesterol (1) or the corresponding acetate with potassium permanganate under neutral or slightly basic conditions is the all-cis-epoxydiol 2. Minor products are the 3j3,5a,6a-trihydroxy-A -steroid and the 3fi,5a,6a,7a-tetrahydroxy-A - and A -steroids, probably formed from 2 by cleavage and dehydration. A precedent for the formation of 2 is the permanganate oxidation of 1,3-cyclohexadiene to an all c/s-epoxydiol in unspecified yield. ... 

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