- Mechanism of error caused by isotope-labeled internal standard: Accurate method for simultaneous measurement of vitamin D and pre-vitamin D by liquid chromatography/tandem mass spectrometry
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Rationale Bias of up to 25% has been observed for vitamin D3 and D2 samples exposed to heating during sample preparation, even when isotope-labeled internal standards are used. The goals of this study were to identify the mechanism of the positive bias observed in measuring vitamin D 3 and D2 by liquid chromatography/tandem mass spectrometry (LC/MS/MS) and determine a way to eliminate the error source. METHODS Several internal standards with varying locations of labeling were used for comparison in this study. Additionally, different temperatures (25, 37, 55, and 75 °C) and different treatment times were investigated for sample preparation and a LC/MS/MS method capable of simultaneously measuring vitamin D and pre-vitamin D was developed. RESULTS It was demonstrated that the different conversion behaviors of the analyte and the internal standard were the cause of the positive bias. This bias was eliminated when internal standards with labeling remote from the double-bond area of the molecules were used. Additionally, sample preparation was shortened from overnight saponification at room temperature to 0.5 h at 75 °C. CONCLUSIONS The use of an internal standard with labeling remote from the conjugated area eliminated the error source and gave accurate correction at all of the temperatures investigated. Heating may be used for rapid sample preparation as an alternative to overnight saponification at room temperature. This work not only describes the mechanism of an inaccurate internal standard correction, but also establishes a rapid LC/MS/MS method for simultaneous measurement of vitamin D and pre-vitamin D.
- Huang, Min,Cadwallader, Amy B.,Heltsley, Rebecca
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- Studies of the antenna effect in polymer molecules. 24. Solar photosynthesis of previtamin D3 in aqueous solutions of poly(sodium styrenesulfonate-co-2-vinylnaphthalene)
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The photochemical step in the synthesis of vitamin D3 in an aqueous solution of poly(sodium styrenesulfonate-co-2-vinylnaphthalene) (PSSS-VN) was studied using solar light. The photoisomerization of 7-dehydrocholesterol to previtamin D3 was found to be exceptionally clean and efficient. The process was shown to be photosensitized by the pendant naphthalene chromophores in the copolymer via singlet-singlet energy transfer. The lack of tachysterol, a major side product formed during photoisomerization in organic solution, was explained by triplet-sensitized isomerization of tachysterol to previtamin. Triplet-triplet energy transfer from excited polymeric naphthalene chromophores to tachysterol is efficient because of the high local concentration of tachysterol in the vicinity of the energy donors.
- Nowakowska, Maria,Foyle, Victor P.,Guillet, James E.
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- Kinetics of thermal [1,7A]-sigmatropic shift of hexafluoro vitamin D3 and vitamin D3 derivatives. Evaluation of conformations of the A ring affected by 1-OH and 3-OH groups
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The quantitative evaluation of the [1,7a]-sigmatropic rearrangement of vitamin D3 and its analogs affected by the conformations of the A ring using the 1H-NMR method was described. Although the side chain of the D ring had no effect on the hydrogen migration, the rearrangement was influenced by the hydroxy groups of the A ring.
- Igarashi, Jun-Etsu,Ikeda, Masahiko,Sunagawa, Makoto
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- Ring Opening in the Dehydrocholesterol-Previtamin D Dystem Studied by Ultrafast Spectroscopy
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The rate of the electrocyclic ring opening of 7-dehydrocholesterol to previtamin D is investigated by transient absorption spectroscopy with a time resolution better than 300 fs.The dehydrocholesterol, which is a derivative of 1,3-cyclohexadiene, is excited around 267 nm.The primary product, the s-cis,Z,s-cis conformer of the triene previtamin D, appears with a time constant of 5.2 ps.This result is consistent with literature data.We found that it is temperature independent.So there is no activation energy for this electrocyclic ring opening.A barrierless process, on the other hand, is expected to proceed much faster (in about 1E-13 s), unless there is an entropy of activation.The results suggest that the molecule reaches within a few femtoseconds the lowest excited state (2A1) of the product, from where it goes on through an entropic bottleneck.The primary product isomerizes thermally to the stable s-cis,Z,s-trans conformer of previtamin D within 125 ps in ethanol at room temperature.This time is much longer than the reported corresponding time in the cyclohexadiene/hexatriene system.We found that it depends on the solvent viscosity and on the temperature.The activation energy was determined to be 15.5 +/- 1.0 kJ/mol.
- Fuss, Werner,Hoefer, Thomas,Hering, Peter,Kompa, Karl L.,Lochbrunner, Stefan,et al.
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- ORGANIC REACTIONS AT HIGH PRESSURE. INTERCONVERSION OF PREVITAMIN D3 AND VITAMIN D3.
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The interconversion of previtamin D3 and vitamin D3 at 20 deg C was effected at high pressure (15 kbar) in three solvent mixtures.The rate constants of k1 and k2 were determined to be 30 to 45 times larger than the corresponding 1 bar rate constants.The ΔV* was calculated to be -5.14 cm3/mol or lower, indicating a concerted sigmatropic hydrogen shift.
- Dauben, William G.,Kowalczyk, Bruce A.,Funhoff, Dirk J. H.
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- Effects of surface adsorption and confinement on the photochemical selectivity of previtamin D3 adsorbed within porous sol-gel derived alumina
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It has been demonstrated that porous sol-gel derived (SGD) alumina can function as an effective microorganized medium in which to perform size- or shape-selective organic transformations. For the photolysis of 7- dehydrocholesterol (7D) encapsulated within SGD-alumina, it was found that the adsorption characteristics of 7D and the pore size of the SGD-alumina greatly influenced the photochemical selectivity of the cis-trans isomerization of previtamin D3 to tachysterol3. An increase in the ratio of previtamin D3 (P3) to tachysterol3 (T3) was obtained on photolysis of 7D adsorbed within SGD-alumina with a pore size of 10-20 ?. This result is attributed to a confinement effect that inhibits the cis-trans isomerization of P3 to T3. In addition to the confinement effect on the photochemical selectivity, it was found that the adsorption characteristics of 7D to the surface of SGD-alumina also play a critical role in the photochemical selectivity. The results indicate that confinement in addition to chemisorption via the 3-hydroxyl group of 7D to the surface of activated SGD- alumina is necessary to optimize the photochemical selectivity. The presented results also provide direct experimental evidence to demonstrate that adsorption solely to a metal oxide surface via the 3-hydroxyl group is not sufficient to inhibit the cis-trans isomerization of P3 to D3.
- Schultz, Forrest S.,Anderson, Marc A.
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- Biomimetic Synthesis of Chaxine and its Related Compounds
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The highly oxidized natural products chaxine B and BB have been synthesized from ergosterol in eight steps according to a route inspired by their proposed biosynthesis; key steps were an oxidative cascade from a furan intermediate to an enol ester using m-chloroperbenzoic acids (MCPBA), followed by diastereoselective epoxidation and acyloxy migration. This concise synthesis resulted in the revision of the structures of chaxine B and its naturally occurring analogs and syntheses of the unnatural analogues of these natural products for biological investigations.
- Niki, Misaki,Hirata, Yushi,Nakazaki, Atsuo,Wu, Jing,Kawagishi, Hirokazu,Nishikawa, Toshio
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p. 4848 - 4860
(2020/05/08)
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- Photo-conversion of two epimers (20R and 20S) of pregna-5,7-diene-3β, 17α, 20-triol and their bioactivity in melanoma cells
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Pregna-5,7-dienes and their hydroxylated derivatives can be formed in vivo when there is a deficiency in 7-dehydrocholesterol (7-DHC) Δ-reductase function, e.g., Smith-Lemli-Opitz syndrome (SLOS). Ultraviolet B (UVB) radiation induces photoconversion of 7-DHC to vitamin D3, lumisterol3 and tachysterol3. Two epimers (20R and 20S) of pregna-5,7-diene-3β,17α,20-triol (4R and 4S, respectively) were synthesized and their UVB photo-conversion products identified as corresponding 9,10-secosteroids with vitamin D-like and tachysterol-like structures, and 5,7-dienes with inverted configuration at C-9 and C-10 (lumisterol-like). The number and character of the products and the dynamics of the process were dependent on the UVB dose. At high UVB doses, the formation of multiple oxidized derivatives of the primary products, and the formation of 5,7,9(11)-triene, were observed. The production of vitamin D-like, tachysterol-like and lumisterol-like derivatives was also observed in human skin treated with 4R and 4S, and subjected to UV irradiation, as shown by RP-HPLC. Newly synthesized compounds inhibited melanoma growth in dose dependent manner, and some of them showed equal or higher potency than 1,25(OH)2D3. In summary, we have characterized for the first time the products of UV induced conversion of pregna-5,7-diene-3β,17α,20-triols and documented that the newly synthesized compounds have antiproliferative properties against melanoma cells.
- Zmijewski, Michal A.,Li, Wei,Zjawiony, Jordan K.,Sweatman, Trevor W.,Chen, Jianjun,Miller, Duane D.,Slominski, Andrzej T.
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p. 218 - 228
(2009/04/14)
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- Ultraviolet irradiation apparatus for photochemical reaction and preparation process of vitamin D derivative making use of the same
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Disclosed herein are an ultraviolet irradiation apparatus for photochemical reactions which can irradiate the photo-reactive solution with ultraviolet rays having a specific wavelength suitable for the intended photochemical reaction at a high efficiency, and a process by which a provitamin D derivative can be converted into a provitamin D derivative at a high efficiency by means of a photochemical reaction by one-step process of light irradiation, thereby preparing a vitamin D derivative at a high efficiency. The ultraviolet irradiation apparatus irradiates the photo-reactive solution with the ultraviolet rays having the specific wavelength through a quartz rod. Specifically, the apparatus is constructed by an electric discharge lamp, a condensing and reflecting mirror and a plane mirror both having wavelength selective property, an optical filter which transmits the ultraviolet rays having the specific wavelength, and a quartz rod on which the ultraviolet rays having the specific wavelength are struck. The photo-reactive solution is irradiated with the ultraviolet rays from the quartz rod. The quartz rod is immersed in the photo-reactive solution, or a reaction vessel is irradiated with the ultraviolet rays from the quartz rod. In the preparation process of the vitamin D derivative, an ultraviolet irradiation apparatus for photochemical reactions having an ultraviolet radiation-emitting lamp, an optical system having wavelength selective property and a quartz rod on which the ultraviolet rays having the specific wavelength from the optical system are struck is used, and a solution of a provitamin D derivative is irradiated with the ultraviolet rays having the specific wavelength emitted from the quartz rod to cause a photochemical reaction of the provitamin D derivative solution, thereby forming a previtamin D derivative. The previtamin D derivative is further subjected to a thermal isomerization reaction to prepare the vitamin D derivative.
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- Thermal -Sigmatropic Shift of Previtamin D3 to Vitamin D3: Synthesis and Study of Pentadeuterio Derivatives
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Specifically pentadeuteriated previtamin D3 11 has been synthesized to impart thermal stability to the otherwise labile material.A 12-step synthesis of the trideuteriated A-ring 14b from p-methoxyphenol was developed and employed the addition of (methyl-d3)magnesium iodide to either the keto thiomethylene intermediate 23 or the keto dioxane 27.The enantiomerically pure trideuterio A-ring (-)-14b was then coupled with the deuteriated CD fragment 13b followed by hydrogenation to afford pentadeuteriated previtamin D3 11.A primary deuterium kinetic isotope effect (KIE) study of the -sigmatropic hydrogen migration in the conversion of previtamin D3 to vitamin D3 indicated a more "normal" primary deuterium isotope effect (as compared to a previously reported literature value of ca. 45).At 80 deg C, a kH/kD for the previtamin D3 to vitamin D3 isomerization was determined to be ca. 6.2.At 25 deg C, this -sigmatropic hydrogen migration proceeds with a kH/kD of ca. 11.4.The revisible, first-order -sigmatropic hydrogen shift of previtamin D3 to D3, determined over the temperature range 60.1-85.5 deg C is characterized by the following activation parameters: log AH = 8.8 and EaH = 19.6 kcal/mol.Deuteriated pre-D3, which rearranges over this temperature range, is characterized by the activation parameters log AD = 9.5 and EaD = 21.9 kcal/mol.
- Okamura, William H.,Elnager, Hassan Y.,Ruther, Michael,Dobreff, Susanne
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p. 600 - 610
(2007/10/02)
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- Novel Photosensitizers for the E/Z-Isomerization of Trienes. Part 1. Synthesis and Application
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Uranine and its thioxanthene and selenoxanthene analogues, as well as the disodium salts of o-(6-hydroxy-3-oxo-3H-xanthen-9-yl)benzenesulphonic acid and its thioxanthene and selenoxanthene analogues, show different photosensitizer properties in the E/Z-isomerization of trienes.This has been verified by applying them to the technically useful conversion of tachysterol into previtamin D.The synthesis of the novel photosensitizers with thioxanthene and selenoxanthene moieties are also described.
- Pfoertner, Karl-Heinz
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p. 523 - 526
(2007/10/02)
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- Determination of the Molar Absorptivity (ε) of the Photoisomers of 3β-Hydroxy-cholest-5,7-diene (Provitamin D3)
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A method is described which allows the determination of the molecular absorptivity (ε) of all components in a four-component system and is applied to the ε-determination of the photoisomers of provitamin D3 (1): praevitamin D3 (2), lumisterol3 (3), and tachysterol3 (4).By means of irradiation with appropriate wavelengths the four-component system is reduced to a two- and a three-component system, respectively, and the unknown molar absorptivities are evaluated numerically or graphically.
- Gliesing, S.,Reichenbaecher, M.,Ilge, H.-D.,Fassler, D.
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p. 311 - 320
(2007/10/02)
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- 1α-HYDROXY PREVITAMIN D3 AND ITS SELECTIVE FORMATION FROM 1-KETO PREVITAMIN D3
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An efficient method for the preparation of crystalline 1α-hydroxy previtamin D3 is described.Also the stereoselective reduction of 1-keto previtamin 9 is discussed; it was observed that with aluminium hydride 7 is the most abundant product.This stands in contrast with previously reported LiAlH4 and NaBH4 mediated reductions.
- Vanmaele, L. J.,Clercq, P. J. De,Vandewalle, M.,Halkes, S. J.,Overbeek, W. R. M.
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p. 1179 - 1182
(2007/10/02)
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- Calciferol and its Relatives. Part 27. A Synthesis of 1α-Hydroxyvitamin D3 by way of 1α-Hydroxytachysterol3
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A new synthesis of 1α-hydroxyvitamin D3 is described.The bis-t-butyldimethylsilyl ether (17) of (3S,5R)-3,5-dihydroxy-2-methylcyclohex-1-enecarbaldehyde and 8-p-tolylsulphonylmethyl-des-AB-cholest-8-ene (4) were combined to give mixed benzoyloxysulphones which, on reductive elimination with sodium amalgam, gave the corresponding bis-ether of 1α-hydroxytachysterol3.This was isomerised photochemically to the bis-ether of 1α-hydroxyprecalciferol3, and then thermally to give the bis-ether of 1α-hydroxyvitamin D3.Removal of protecting groups gave 1α-hydroxyvitamin D3 (21) in 62percent yield from the sulphone (4), or 12.8percent overall from cholesterol.
- Kocienski, Philip J.,Lythgoe, Basil
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p. 1400 - 1404
(2007/10/02)
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