- Oxidation of dihydrotestosterone by human cytochromes P450 19A1 and 3A4
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Dihydrotestosterone is a more potent androgen than testosterone and plays an important role in endocrine function. We demonstrated that, like testosterone, dihydrotestosterone can be oxidized by human cytochrome P450 (P450) 19A1, the steroid aromatase. The products identified include the 19-hydroxy-and 19-oxo derivatives and the resulting Δ1,10-, Δ5,10-, and Δ9,10-dehydro 19-norsteroid products (loss of 19-methyl group). The overall catalytic efficiency of oxidation was ～10-fold higher than reported for 3α-reduction by 3α-hydroxysteroid dehydrogenase, the major enzyme known to deactivate dihydrotestosterone. These and other studies demonstrate the flexibility of P450 19A1 in removing the 1- and 2-hydrogens from 19-norsteroids, the 2-hydrogen from estrone, and (in this case) the 1-, 5β-, and 9β-hydrogens of dihydrotestosterone. Incubation of dihydrotestosterone with human liver microsomes and NADPH yielded the 18- and 19-hydroxy products plus the Δ1,10-dehydro 19-nor product identified in the P450 19A1 reaction. The 18- and 19-hydroxylation reactions were attributed to P450 3A4, and 18- and 19-hydroxydihydrotestosterone were identified in human plasma and urine samples. The change in the pucker of the A ring caused by reduction of the Δ4,5 bond is remarkable in shifting the course of hydroxylation from the 6β-, 2β-, 1β-, and 15β-methylene carbons (testosterone) to the axial methyl groups (18, 19) in dihydrotestosterone and demonstrates the sensitivity of P450 3A4, even with its large active site, to small changes in substrate structure.
- Cheng, Qian,Sohl, Christal D.,Yoshimoto, Francis K.,Guengerich, F. Peter
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p. 29554 - 29567,14
(2012/12/12)
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- Oxidation of dihydrotestosterone by human cytochromes P450 19A1 and 3A4
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Dihydrotestosterone is a more potent androgen than testosterone and plays an important role in endocrine function. We demonstrated that, like testosterone, dihydrotestosterone can be oxidized by human cytochrome P450 (P450) 19A1, the steroid aromatase. The products identified include the 19-hydroxy-and 19-oxo derivatives and the resulting Δ1,10-, Δ5,10-, and Δ9,10-dehydro 19-norsteroid products (loss of 19-methyl group). The overall catalytic efficiency of oxidation was ～10-fold higher than reported for 3α-reduction by 3α-hydroxysteroid dehydrogenase, the major enzyme known to deactivate dihydrotestosterone. These and other studies demonstrate the flexibility of P450 19A1 in removing the 1- and 2-hydrogens from 19-norsteroids, the 2-hydrogen from estrone, and (in this case) the 1-, 5β-, and 9β-hydrogens of dihydrotestosterone. Incubation of dihydrotestosterone with human liver microsomes and NADPH yielded the 18- and 19-hydroxy products plus the Δ1,10-dehydro 19-nor product identified in the P450 19A1 reaction. The 18- and 19-hydroxylation reactions were attributed to P450 3A4, and 18- and 19-hydroxydihydrotestosterone were identified in human plasma and urine samples. The change in the pucker of the A ring caused by reduction of the Δ4,5 bond is remarkable in shifting the course of hydroxylation from the 6β-, 2β-, 1β-, and 15β-methylene carbons (testosterone) to the axial methyl groups (18, 19) in dihydrotestosterone and demonstrates the sensitivity of P450 3A4, even with its large active site, to small changes in substrate structure.
- Cheng, Qian,Sohl, Christal D.,Yoshimoto, Francis K.,Guengerich, F. Peter
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p. 29554 - 29567
(2013/01/14)
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- Synthesis of catechols from phenols via Pd-catalyzed silanol-directed C-H oxygenation
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A silanol-directed, Pd-catalyzed C-H oxygenation of phenols into catechols is presented. This method is highly site selective and general, as it allows for oxygenation of not only electron-neutral but also electron-poor phenols. This method operates via a silanol-directed acetoxylation, followed by a subsequent acid-catalyzed cyclization reaction into a cyclic silicon-protected catechol. A routine desilylation of the silacyle with TBAF uncovers the catechol product.
- Huang, Chunhui,Ghavtadze, Nugzar,Chattopadhyay, Buddhadeb,Gevorgyan, Vladimir
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supporting information; experimental part
p. 17630 - 17633
(2011/12/16)
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- An expedient one-pot entry to catecholestrogens and other catechol compounds via IBX-mediated phenolic oxygenation
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A one-pot procedure for the preparation of catecholestrogens in over 90% yield is reported, involving oxygenation of 17β-estradiol or estrone with o-iodoxybenzoic acid (IBX) followed by reduction with methanolic NaBH 4. The procedure, which was extended to the o-hydroxylation of a number of representative phenols in good-to-high yields, expands significantly the scope of phenolic oxidation mediated by IBX.
- Pezzella, Alessandro,Lista, Liliana,Napolitano, Alessandra,D'Ischia, Marco
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p. 3541 - 3544
(2007/10/03)
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- Synthesis of the catechols of natural and synthetic estrogens by using 2-iodoxybenzoic acid (IBX) as the oxidizing agent
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A method for the synthesis of 2-hydroxyestrone/estradiol, 4-hydroxyestrone/estradiol, 3′-hydroxydiethylstilbestrol, 3′-hydroxyhexestrol, and 3′-hydroxydienestrol is reported, in which 2-iodoxybenzoic acid (IBX) and the corresponding phenolic estrogen are reacted. Treatment of the natural estrogens, estrone/estradiol, with stoichiometric amounts of IBX in dimethylformamide initially yielded a mixture of estrone/estradiol-2,3- and -3,4-quinones, which were reduced in situ to the corresponding catechols by treatment with a 1 M aqueous solution of ascorbic acid. Chromatographic separation of the reaction products afforded 2- and 4-hydroxyestrone/estradiol in good overall yields (79%). In the case of the synthetic estrogens containing two identical phenolic rings, protection of one ring is a prerequisite for the synthesis of the monocatechol. Thus, diethylstilbestrol and dienestrol were protected at one phenol ring as their methyl ethers. The resulting monophenols were treated with stoichiometric amounts of IBX for 1 h, followed by treatment with 1 M aqueous ascorbic acid to obtain the corresponding catechols in more than 70% yield. Furthermore, the catechol of diethylstilbestrol, protected at one ring, was reduced by catalytic hydrogenation at the C3-C4 double bond to obtain 3′-hydroxyhexestrol in 90% yield. Removal of the protected methoxy groups of the synthetic estrogen catechols was carried out by treatment with a 1 M solution of boron tribromide in dichloromethane. This method is highly efficient for the preparative scale synthesis of catechols of both natural and synthetic estrogens.
- Saeed, Muhammad,Zahid, Muhammad,Rogan, Eleanor,Cavalieri, Ercole
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p. 173 - 178
(2007/10/03)
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- Roles of cytochromes P450 1A2 and 3A4 in the oxidation of estradiol and estrone in human liver microsomes
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Of seven cDNA-expressed human cytochrome P450 (P450) enzymes (P450s 1A2, 2B6, 2C9, 2C19, 2D6, 2E1, and 3A4) examined, P450 1A2 was the most active in catalyzing 2- and 4-hydroxylations of estradiol and estrone. P450 3A4 and P450 2C9 also catalyzed these reactions although to lesser extents than P450 1A2. P450 1A2 also efficiently oxidized estradiol at the 16α-position but was less active in estrone 16α-hydroxylation; the latter reaction and also estradiol 16α-hydroxylation were catalyzed by P450 3A4 at significant levels. Anti-P450 1A2 antibodies inhibited 2- and 4-hydroxylations of these two estrogens catalyzed by liver microsomes of some of the human samples examined. Estradiol 16α-hydroxylation was inhibited by both anti-P450 1A2 and anti-P450 3A4, while estrone 16α-hydroxylation was significantly suppressed by anti-P450 3A4 in human liver microsomes. Fluvoxamine efficiently inhibited the estrogen hydroxylations in human liver samples that contained high levels of P450 1A2, while ketoconazole affected these activities in human samples in which P450 3A4 levels were high. α- Naphthoflavone either stimulated or had no effect on estradiol hydroxylation catalyzed by liver microsomes; the intensity of this effect depended on the human samples and their P450s. Interestingly, in the presence of anti-P450 3A4 antibodies, α-naphthoflavone was found to be able to inhibit estradiol and estrone 2-hydroxylations catalyzed by human liver microsomes. The results suggest that both P450s 1A2 and 3A4 have major roles in oxidations of estradiol and estrone in human liver and that the contents of these two P450 forms in liver microsomes determine which P450 enzymes are most important in hepatic estrogen hydroxylation by individual humans. P450 3A4 may be expected to play a more important role for some of the estrogen hydroxylation reactions than P450 1A2. Knowledge of roles of individual P450s in these estrogen hydroxylations has relevance to current controversies in hormonal carcinogenesis.
- Yamazaki, Hiroshi,Shaw, Peter M.,Guengerich, F. Peter,Shimada, Tsutomu
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p. 659 - 665
(2007/10/03)
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- Synthesis of W-acetylcysteine conjugates of catechol estrogens
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The synthesis of N-acetylcysteine conjugates of 2-hydroxyestrone (2-OHE1) and 4-hydroxyestrone (4-OHE1) is described. The reaction of estrone 2,3-quinone with N-acetylcysteine provided 2-OHE1 and its C-4 and C-1 thioether conjugates in a ratio of 1:1, while estrone 3,4-quinone with N-acetylcysteine gave 4-OHE, and its C-2 thioether conjugate as a sole product. Their structures were characterized by inspection of NMR spectra, chemical derivatization (methylation and acetylation), and comparison with the reactivity of 4-bromoestrone 2,3-quinone or 2-bromoestrone 3,4-quinone toward N-acetylcysteine.
- Suzuki, Emako,Iwasaki, Ryo,Goto, Junichi,Matsuki, Yasuhiko,Nambara, Toshio
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p. 296 - 301
(2007/10/03)
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- Participation of the 19-Substituent in the Conversion of 19-Hydroxyandrost-4-ene-3,17-dione into the Corresponding 4,5-Diosphenol
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The synthesis of 4,19-dihydroxyandrost-4-ene-3,17-dione from 19-hydroxy-4β,5-epoxy-5β-androstane-3,17-dione and from 4β,5,19-trihydroxy-5β-androstane-3,17-dione is described.Under various reaction conditions other products are obtained as a result of participation of the 19-hydroxy group to form cyclic ethers.The formation of two of these products, 4α,5-isopropylidene-3α-hydroxy-3β,19-epoxy-5α-androstan-17-one and 4α-hydroxy-4β,19-epoxy-5α-androstane-3,17-dione, can be avoided by treatment of the aforementioned trihydroxy dione with acetic acid in the presence of HCl.
- Hrycko, Sophia,Morand, Peter
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p. 2899 - 2904
(2007/10/02)
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- A NEW SYNTHETIC ROUTE TO 2-HYDROXYL STEROIDAL ESTROGENS VIA ACETYLATION AND DAKIN OXIDATION
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This paper describes a new two-step synthetic route to 2-hydroxy estrogens from either estrone or estradiol, via 2-acetylation followed by Dakin oxidation.This approach is characterized by its simplicity and excellence of yield.
- Xie, Ru-gang,Deng, Li-sen,Gu, Hai-quan,Fan, Ya-ming,Zhao, Hua-ming
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p. 389 - 392
(2007/10/02)
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