Calciferols

Isomerization of double bonds in vitamin D analogs such as calciferol by oxidation and reduction has been carried out via the formation of the tt-allylpalladium complex 334 with PdCl2(PhCN)2 in 70% yield, followed by hydride reduction to afford 335[295],... 

The common name vitamin D is used throughout the pharmaceutical kidustry for simplicity. The trivial name calciferol has also been used extensively with the prefix ergo- and chole-, which kidicate vitamin D2 (2) and vitamin (4), respectively (see Steroids). Vitamin D2 was originally named calciferol in 1931 by Angus and co-wotkets (2). Historically, a number of substances were referred to as vitamin D and were distinguished from one another by a subscript numeral, eg, vitamin D2, vitamin D, etc. 

Calciferol, when hydrogenated catalyticaky, took up 4 moles of hydrogen and gave a compound with the empirical formula C2gH 2D. Sodium in ethanol reduction gave a dihydroproduct that reacted with 3 moles of perbenzoic acid, thus demonstrating the derivative to have three double bonds. 

The irradiation of calciferol in the presence of iodine leads to the formation of 5,6-/n7 j -vitaniin D2 [14449-19-5] (31) or [22350 1-0] (32) (67,68). 5,6-/ra j -Vitainin D as well as vitamin D (2) or (4) can be converted to isovitamin D by treatment with mineral or Lewis acids. Isocalciferol (35) [469-05-6] or (36) [42607-12-5] also forms upon heating of 5,6-/ -vitamin D. Isotachysterol (33) [469-06-7] or (34) [22350-43-2] forms from isocalciferol or vitamin D upon treatment with acid, and its production appears to be the result of sequential formation of trans- and isocalciferol from calciferol. These reactions are the basis of the antimony trichloride test for vitamin D (69—72). 

An especially important case is the thermal equilibrium between precalciferol (pre-vitamin Dj, 22) and calciferol (vitamin D2, 23). ... 

Dihydroxyprecholecalciferol A solution of ia,25-diacetoxyprecholecalciferol (0.712 g, 1.42 mmols), potassium hydroxide (2.0 g, 35.6 mmols) and methanol (40 ml) was stirred at room temperature under argon for 30 hours. The reaction mixture was concentrated under reduced pressure. Water (50 ml) was added to the residue and the mixture was extracted with methylene chloride (3 x 100 ml). The combined organic extracts were washed with saturated sodium chloride solution (3 x 50 ml), dried over anhydrous sodium sulfate, filtered and evaporated under reduced pressure to give 0.619 g of 10f,25-dihydroxyprechole-calciferol asa thick oil. 

Natabec (Warner-Lambert) Slerogyl (Roussel) USA Calciferol (Schwarz) ... 

Quinine alkaloids (quinine, cinchonine), barbiturate derivatives, retinol, calciferol and chole-calciferol... 

D Calciferol Maintenance of calcium balance enhances intestinal absorption of Ca and mobilizes bone mineral Rickets = poor mineralization of bone osteomalacia = bone demineralization... 

Calandria evaporator, in sodium chloride solution mining, 22 804 Calcicard, molecular formula and structure, 5 97t, 118t Calciferols, 25 791-793 dietary sources of, 25 793 Calcination, 2 353, 403, 407—410 12 726-727... 

An X-ray crystal structure determination of calciferol (vitamin D-2,71) showed that steric crowding in the s-cis diene system resulted in a twisted conformation with a dihedral angle of 53° [59], On irradiation with a mercury lamp, it was partially converted into ergosterol (72) and tachysterol (73) [60, 61]. When a solution of calciferol in light petroleum containing a trace of iodine was exposed to diffuse daylight, the vitamin was photoisomerized to (74) [62],... 

Cholecalciferol (vitamin D-3) differs from calciferol only in the alkyl side-chain, so it was assumed to be in the twisted conformation (75a). In alcoholic solution, vitamin D-3 was irradiated with a mercury arc lamp through a cupric sulphate solution filter to give wavelengths above 250 nm. Six products were isolated. Conformation (75a) could reasonably give rise to the assigned structures (76a), (77a) and (78a) (Scheme 2.3). Photoisomerization could give conformation (75b), which would explain the isolation of (76b), (77b) and (78b). The report is confident on four of the new compounds, but notes that the cyclobutene structures (78a) and (78b) are tentatively assigned [63]. 

Cyclization adrenaline azathioprine calciferol chlordiazepoxide cholecalciferol clomiphene hydroxychloroquine levodopa methotrexate phenylalanine tyrosine... 

Isomerization calciferol chlorprothixene cholecalciferol clomiphene clopenthixol pyrithione reserpine sulpyrine tetracycline... 

Vitamin D (calciferol) Produced in skin by action of ultraviolet Controls calcium uptake into the body and... 

The effects of the steroid hormone calcitriol (see p. 330) in bone are complex. On the one hand, it promotes bone formation by stimulating osteoblast differentiation (top). This is particularly important in small children, in whom calcitriol deficiency can lead to mineralization disturbances (rickets see p.364). On the other hand, calcitriol increases blood Ca "" levels through increased Ca "" mobilization from bone. An overdose of vitamin D (chole-calciferol), the precursor of calcitriol, can therefore have unfavorable effects on the skeleton similar to those of vitamin deficiency (hypervitaminosis see p.364). 

The vitamin and metabolic derivatives of a fat-soluble substance calciferol. These antirachitic vitamins are produced from A -unsaturated sterols upon irradiation with ultraviolet light. Population biologists have adduced strong evidence for the hypothesis that lighter skin color, the primary characteristic of race, is related to the lower solar radiance in northern climes. Vitamin D plays a central role in calcium metabolism, both in terms of... 

Vitamin D preparations that are available include er-gocalciferol (also termed calciferol, or vitamin D2), cholecalciferol (vitamin D3), alfa-calcidol (la-hydroxycholecalciferol) and calcitriol (1,25-hydroxycholcalciferol). 

VII.a.2.2. Treatment. Treatment of established vitamin D deficiency requires much larger doses of vitamin D, such as calciferol tablets of 1 mg (40,000 units) daily. Newer but more expensive preparations such as alfa-calcidol and calcitriol are very effective, and are particularly valuable in patients with renal failure who are unable to hydroxylate calciferol. Patients treated with pharmacological doses of vitamin D preparations must be monitored by checking serum calcium at regular intervals because of the risk of inducing hypercalcaemia. This should always be suspected if patients develop thirst, nausea or vomiting. The newer hydroxylated preparations have a shorter effective half-life, and therefore problems of overdosage are quicker to resolve once identified. 

Vitamin D is the collective term for a group of compounds formed by the action of ultraviolet irradiation on sterols. Cholecalciferol (vitamin D3) and calciferol (vitamin D2) are formed by irradiation of the provitamins 7-dehydrocholesterol and ergosterol, respectively. The conversion to vitamin D3 occurs in the skin. The liver is the principal storage site for vitamin D, and it is here that the vitamin is hydroxylated to form 25-hydroxyvitamin D. Additional hydroxylation to form 1,25-dihydroxyvita-min D occurs in the kidney in response to the need for calcium and phosphate. A discussion of the role of vitamin D in calcium homeostasis is provided in Chapter 66. 

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