Cholesterol, 7-dehydro

Dehydrocholesterin Dehydrocholesterol. See 7-Dehydrocholesterol 7-Dehydrocholesterol CAS 434-16-2 EINECS/ELINCS 207-100-5 Synonyms Cholesta-5,7-dien-3-ol Cholesta-5,7-dien-3-ol, (3-P)- Cholesta-5,7-dien-3-P-ol 5,7-Cholestadien-3-p-ol 5 7-Cholesterol 5 Cholesterol Cholesterol, 7-dehydro- 7-Dehydrocholesterin Dehydrocholesterol (-)-7-Dehydrocholesterol... 

A steroid very closely related structurally to cholesterol is its 7 dehydro derivative 7 Dehydrocholesterol is formed by enzymatic oxidation of cholesterol and has a conju gated diene unit m its B ring 7 Dehydrocholesterol is present m the tissues of the skin where it is transformed to vitamin D3 by a sunlight induced photochemical reaction... 

Properties 7-Dehydro-cholesterol Ergosterol Vitamin D2 Vitamin... 

The biosynthesis of pregnenelone (112) in mammals has been well documented [1] it is known to be produced from cholesterol (1) via its 20,22-dihydroxy derivative (121) (Scheme 19A). The origin of 112 has been investigated in the sponge Amphimedon compressa. At the present time it is not known whether cholesterol and its 20,22-dihydroxy derivative serve as precursors for this pregnane in A. compressa however a new pathway (Scheme 19B) has been found to operate [89]. This involves the conversion of 22-dehydro sterols (e.g. stigmasterol, 122) to pregnenelone. The mechanism is believed to... 

Serum sex hormones effect. DION (300 mg androstenedione, 150 mg dehydro-epiandrosterone, 540 mg saw palmetto, 300 mg indole-3-carbinol, 625 mg chrysin, 750 mg Tribulus terrestris), administered daily to healthy 30- to 59-year-old men for 28 days, produced no change in serum concentrations of total T and PSA. DION increased the concentrations of serum androstenedione (342%), free T (38%), DHT (71%), and estradiol (103%). Serum high-density lipoprotein (HDL) cholesterol concentrations were reduced by 5 mg/dL in DION (p < 0.05). Increases in serum free T (r = 0.01), androstenedione (r = 0.01), DHT (r = 0.03), or estradiol (r = 0.07) concentrations in DION were not related to age. The ingestion of androstenedione combined with herbal products increased serum-free T concentrations in older men, but herbal products did not prevent the conversion of... 

The 1,4-addition of alkyl cyanocupratcs to epoxides to form cyclic a,ft-unsalurated ketones provides a stereoselective method for conversion of dehydro-. cpiandrosteronc into cholesterol (4) and other related steroids. Thus the keto epoxide 2 (obtained from dehydroepiandrosterone in 55% overall yield in three steps) reacts with lithium isohcxylcyanocupratc to give the adduct 3, which can be converted to cholesterol (4) in several known steps.27... 

The last sequence of reactions in the biosynthesis of choles-terol involves approximately 20 enzymatic steps, starting with lanosterol. In mammals the major route involves a series of double-bond reductions and demethylations (fig. 20.10). The sequence of reactions involves reduction of the A24 double bond, the oxidation and removal of the 14a methyl group followed by the oxidation and removal of the two methyl groups at position 4 in the sterol. The final reaction is a reduction of the A7 double bond in 7-dehydro-cholesterol. An alternative pathway from lanosterol to cholesterol also exists. The enzymes involved in the transformation of lanosterol to cholesterol are all located on the endoplasmic reticulum. 

Vitamin D-active substances are required in the diets of growing children and pregnant women, but normal adults receiving sufficient doses of sunshine can manufacture sufficient amounts of these compounds to meet their needs. Active vitamin D compounds can by synthesized in such individuals from 7-dehydro-cholesterol (see Table 6.2), an intermediate in cholesterol biosynthesis. Dietary sources also include cholecalciferol, which is produced from 7-dehydrocholesterol and ergosterol (Table 6.2). 7-Dehydrocholesterol and ergosterol are often referred to as provitamins. 

Q-11 What is the structural difference between pro-vitamin D (7-dehydro cholesterol) in the skin and ergosterol ... 

Fig. 2. Activity of homogeneous SCP2 as measured in the activation of the conversion of 7-dehydro-cholesterol to cholesterol by rat liver microsomes. Incubations were conducted as described [21] except that the incubation volume was 0.6 ml. (A) Cholesterol formed is plotted as a function of SCPj protein. (B) Cholesterol formed is plotted as a function of cholesterol formed per mg of SCPj.

It is worthy of note that low stereospecificity in utilizing 24-stereoisomers of 24-methylcholesterol was demonstrated with Manduca sexta. However, it was reported that in Dermestes maculatus there was a preference for (24/ )-alkylsterols (acetate) over 24S isomers, and Drosophila melanogaster utilizes both (247 )- and (24S)-methylcholesta-5,7-dien-3/8-ol, while Drosophila pachea preferentially utilizes the 245 isomers and Drosophila mojavensis prefers the 247 isomers as reported by Kircher and Rosenstein [163], Our studies revealed that 24-stereoisomers of 24-methyl- and 24-ethylcholesterols and their 22-dehydro analogues can sustain the growth of the silkworm B. mori and are all converted into cholesterol to a similar extent [164],... 

Since the elucidation of the structure of ecdysone, a number of synthetic cholesterol derivatives have been demonstrated as possible intermediates in the conversion of cholesterol into ecdysone. However, few attempts have been made to isolate the intermediates of ecdysone synthesis in the PG. Only 3j8-hydroxy-5a-cholestan-6-one (111) was isolated from the organ culture medium of the silkworm PG as a possible intermediate [193]. The PG possesses a comparatively large percentage of 7-dehydro-cholesterol (110) in several insects. Thus, 7-dehydrocholesterol may also be a possible early intermediate in the transformation of cholesterol into ecdysone [194]. 

Further products have been identified from the irradiation of 7-dehydro-cholesterol [(130), provitamin D3]. In ether or alcohol the main component of the photolysate was assigned structure (131) which results from the photochemical cyclization of the trans-Z-cis-conformation of the triene (132) formed by ringopening of the cholesterol.92 From reaction in ethanol two alcohol-addition products (133) and (134) have been identified. Two other products of the toxisterol type have been assigned structures (135), the difference between them... 

III. "OVERIRRADIATION PRODUCTS" FROM 7-DEHYDRO-CHOLESTEROL BISCHOLESTADIENOLS... 

The conversion of provitamins to vitamins D in the skin is well known. However, the interesting observations of Glover, Glover, and Morton (1952) should be recorded. Cholesterol is the source of the 7-dehydro-cholesterol, and it is dehydrogenated in the mucous membrane of the small intestine to the provitamin. 

Diosgenin (I) as the acetate or benzoate upon bromination with N-bromosuccinimide followed by dehydrobromination (Rosenkranz, Romo, and Berlin, 1951a) or by application of the Windaus 7-dehydro-cholesterol synthesis (Ringold et al., 1952) yields the corresponding... 

Isolated for the first time in 1775 from gallstones by the physician Benjamin Gottlob Friedrich Conradi (Jena, Germany), cholesterol occurs everywhere in the human body. With high levels especially in the brain, the spinal cord and the suprarenal glands, the total amount of cholesterol in an adult adds up to some 240 grams. Invertebrates, on the other hand, synthesise in addition 24-dehydro-cholesterol in considerable quantity. 

The successful industrial synthesis starts from photolysis of 7-dehydro-cholesterol. 

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