571-22-2Relevant articles and documents
Mild Deprotection of Dithioacetals by TMSCl/NaI Association in CH3CN
Yao, Yunxin,Zhao, Guangkuan,Hamze, Abdallah,Alami, Mouad,Provot, Olivier
, p. 5775 - 5779 (2020/08/17)
A mild process using a combination of TMSCl and NaI in acetonitrile is used to regenerate carbonyl compounds from a variety of dithiane and dithiolane derivatives. This easy to handle and inexpensive protocol is also efficient to deprotect oxygenated and mixed acetals as 1,3-dioxanes, 1,3-dioxolanes and 1,3-oxathianes quantitatively. As a possible extension of this method, it was also shown that nitrogenated substrates such as hydrazones, N-tosylhydrazones, and ketimines reacted well under these conditions to give the expected ketones in high yields. The methodology proposed herein is a good alternative to the existing methods since it does not use metals, oxidants, reducing agents, acidic or basic media, and keto-products were obtained in high to excellent yields.
Bile acid-based 1,2,4-trioxanes: Synthesis and antimalarial assessment(1)
Singh, Chandan,Hassam, Mohammad,Verma, Ved Prakash,Singh, Ajit Shanker,Naikade, Niraj Krishna,Puri, Sunil K.,Maulik, Prakas R.,Kant, Ruchir
, p. 10662 - 10673 (2013/02/23)
A new series of bile acid-based trioxanes 23a-d, 24a-d, 25a-d, 26a, 26b, and 26d have been synthesized and assessed for their antimalarial activity against multidrug-resistant Plasmodium yoelii in Swiss mice by oral route. The antimalarial activity of these trioxanes showed a strong dependence on the side-chain length; shortening side-chain length lead to increase in activity. The antimalarial activity also showed even stronger dependence on the stereochemistry at C3 and C6 (C21 in Figure 5) of the trioxane moiety. Of the two diastereomers isolated of each of the trioxanes, more polar one was significantly more active than the less polar one. The more polar diastereomer of the trioxanes 26a, 26b, and 26d, were the most active compounds of the series. All these three trioxanes provided 100% protection at 24 mg/kg × 4 days. In this model β-arteether provided 100% and 20% protection at 48 mg/kg × 4 days and 24 mg/kg × 4 days, respectively.
Steroidal isomers with uniform mass spectra of their per-TMS derivatives: Synthesis of 17-hydroxyandrostan-3-ones, androst-1-, and -4-ene-3,17-diols
Parr, Maria K.,Zapp, Josef,Becker, Michael,Opfermann, Georg,Bartz, Ulrike,Schaenzer, Wilhelm
, p. 545 - 551 (2008/02/02)
In human sports doping control analysis most of the steroids are analyzed after enzymatic hydrolysis of the glucuronides as per-trimethylsilyl (TMS) derivatives applying gas chromatography-mass spectrometry (GC-MS). According to the recommendations of the World Anti-Doping Agency the identification of analytes should be based on retention time and on mass spectrometric characterization. This study shows that the bis-TMS derivatives of 16 specific C19 steroids, namely the stereoisomers of 5ξ-androst-1-ene-3ξ,17ξ-diol (8 isomers), androst-4-ene-3ξ,17ξ-diol (4 isomers), and 17ξ-hydroxy-5ξ-androstan-3-one (4 isomers), reveal very similar mass spectra. As a rule, when taking the retention times, which are provided as Kovac indices for all these isomers, into account, a restriction to two or three possible isomers is possible. Reliable identification should additionally include a comparison of the retention times of the analytes with the reference compounds measured concomitantly. In some cases standard addition may be appropriate. Due to the limited availability, the above mentioned isomers were synthesized by reduction of the corresponding α,β-unsaturated oxo steroids either with K-Selectride or by catalytic hydrogenation (Pd/C as catalyst). The products of the reactions were identified by means of nuclear magnetic resonance (NMR) characterization and by further reduction to the corresponding 5ξ-androstane-3ξ,17ξ-diols and GC-MS comparison with commercially available reference standards.
Substrate specificity of a mouse aldo-keto reductase (AKR1C12)
Endo, Satoshi,Matsumoto, Kengo,Matsunaga, Toshiyuki,Ishikura, Shuhei,Tajima, Kazuo,El-Kabbani, Ossama,Hara, Akira
, p. 2488 - 2492 (2007/10/03)
AKR1C12, a mouse member of the aldo-keto reductase (AKR) superfamily, is highly expressed in the stomach and is identical to a protein encoded in an interleukin-3-regulated gene in mouse myeloid cells, but its function remains unknown. In this study, the recombinant AKR1C12 was purified to homogeneity and the specificity for coenzymes and substrates was examined at a physiological pH of 7.4. The enzyme reduced various α-dicarbonyl compounds, several ketosteroids, aldehydes and some ketones using NADH as the preferred coenzyme. In the reverse reaction, the enzyme showed coenzyme preference for NAD +, and oxidized 3α-, 17β- and 20α-hydroxysteroids, and non-steroidal aliphatic and alicyclic alcohols, of which many hydroxysteroids and geranylgeraniol were good substrates, exhibiting low K m and high kcat/Km values. The results, together with the intracellular high ratio of NAD+/NADH, suggest that AKR1C12 functions as a dehydrogenase for the endogenous hydroxysteroids and geranylgeraniol in mouse stomach and myeloid cells.
Electrocatalytic Hydrogenation Using Precious Metal Microparticles in Redox-Active Polymer Films
Coche, Liliane,Ehui, Bernadette,Limosin, Daniele,Moutet, Jean-Claude
, p. 5905 - 5910 (2007/10/02)
Glassy carbon felt electrodes have been modified by electrodeposition of poly(pyrrole-viologen) films (derived from N,N'-dialkyl-4,4'-bipyridinium salts), followed by electroprecipitation of precious metal (Pt, Pd, Rh, or Ru) microparticles.The resulting electrodes have been proved to be active for the electrocatalytic hydrogenation of conjugated enones (2-cyclohexen-1-one, cryptone, carvone, isophorone), styrene, and benzonitrile in aqueous media (pH 1).Despite low loading of metal catalysts, high electric and product yields and a long term stability of these cathodes have been observed.The influence of the metal loading and the polymer structure on the catalytic efficiency as well as the selectivity obtained according to the metal catalyst used have been studied.Comparision with results previously reported for other catalytic cathodes like Pt/Pt, Pd/C, or Raney nickel electrodes proves the high efficiency of these microparticles within redox polymer film based electrodes.
The Reduction of Steroid 2α-Fluoro 4-En-3-ones
Goeendos, Gyoergy,McGirr, Larry G.,Jablonski, Chester R.,Snedden, Walter,Orr, James C.
, p. 3057 - 3059 (2007/10/02)
Reduction of testosterone with potassium tri-(R,S)-sec-butylborohydride gives predominantly the allylic 3β-alcohol, while 2α-fluorotestosterone is converted solely to 2α-fluoro-4-androstene-3α,17β-diol, and 2α-fluoro-4-androstene-3,17-dione to 2α-fluoro-3α-hydroxy-4-androsten-17-one.Reduction of testosterone with (R,R)- or (S,S)-Rh-DIOP and dihydrosilanes give predominantly allylic alcohols, while with the same catalysts and monohydrosilanes no allylic alcohols are found, the 4-double bond being instead reduced.The chirality of the DIOP reagents contributes only to a minor extent to stereoselectivity of 3-ketone reduction.
Stereochemistry of the Palladium-catalyzed Hydrogenation of 3-Oxo-4-ene Steroids. V. A Kinetic Study in Basic and Acidic Media
Nishimura, Shigeo,Momma, Yasuhiro,Kawamura, Hideo,Shiota, Michio
, p. 780 - 783 (2007/10/02)
Effects of the β-methyl group at C-10 and some oxygen functions (=O, OH, OAc) at C-11, C-17, and C-20 on the rates of hydrogenation of 3-oxo-4-ene steroids have been studied with palladium catalyst in pyridine or THF/HBr as solvent.In contrast to the hydrogenation in pyridine, the rate in THF/HBr was greatly depressed by the presence of 10β-methyl group.The reactivity of the steroids was enhanced by the oxygen functions, in particular, by 11, 17-dioxo group.The effects of the substituents are discussed from a mechanistic consideration based on the obtained results.
Radical-induced Reduction of α,β-Unsaturated Steroid Ketones with Tributyltin Hydride
Laurent, Henry,Esperling, Peter,Baude, Guenter
, p. 1996 - 1999 (2007/10/02)
Conjugated steroid ketones are reduced stereoselectively with tributyltin hydride in the presence of azobisisobutyronitrile as radical initiator to give the corresponding saturated ketones in high yields.
