- Unexpected formation of O-methoxycarbonyl cyanohydrin showing potential as a protective group of ketones
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A one-step procedure using methyl cyanoformate and a secondary alkylamine was reported to efficiently transform ketones into O- methoxycarbonyl cyanohydrins. This functional group shows interesting potential in protecting group chemistry.
- Poirier, Donald,Berthiaume, David,Boivin, Roch P.
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- One-pot ethynylation and catalytic desilylation in synthesis of mestranol and levonorgestrel
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A one-pot ethylnylation and catalytic desilylation reaction was developed for the synthesis of mestranol and levonorgestrel. Addition of trimethylsilylacetylide to the carbonyl group at C-17 of the steroids yielded the C-17α-trimethylsilylacetylenyl adducts, which were desilylated with a catalytic amount of TBAF (0.050 equiv) in one pot to provide the corresponding mestranol and levonorgestrel both in 90% yields. A plausible mechanism was proposed for the catalytic desilylation through the regeneration of the fluoride ion from the reaction of alkoxide on the steroid with Me3SiF. The one-pot ethynylation and catalytic desilylation methodology provided an alternative route and avoided the traditional use of flammable and explosive acetylene gas toward the synthesis of mestranol and levonorgestrel.
- Wong, Fung Fuh,Chuang, Shih Hsien,Yang, Sheng-chuan,Lin, Yu-Hsiang,Tseng, Wen-Che,Lin, Shao-Kai,Huang, Jiann-Jyh
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- Key structures for the synthesis of steroid antitumor agents. Synthesis of 16-dehydro-17-carbaldehydes of 13β- and 13α-estratriene series
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A convenient preparative synthesis of 3-methoxyestra-1,3,5(10),16-tetraene-17-carb-aldehyde and its epimeric 13α-analog, the key structures in the synthesis of steroid estrogen receptor modulators and potential antitumor agents, was developed starting from estrone and including the generation of intermediate 16-dehydro-17-carbonitriles and their reaction with diisobutylaluminum hydride. The influence of conformational dif erences in the steroid molecules with the natural 13β- and epimeric 13α-configurations on the reactivity of intermediate compounds and the stereoselectivity of the trimethylsilyl cyanide addition to the carbonyl group of methyl ethers of epimeric estrones was considered.
- Tserfas,Kuznetsov, Yu. V.,Levina,Zavarzin
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- N-butyl, N-methyl, 11-[3′, 17′ β-(dihydroxy)-1′,3′,5′(10′)-estratrien-16′ α-yl]-9(R/S)-bromo undecanamide: Synthesis and 17β-HSD inhibiting, estrogenic and antiestrogenic activities
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The synthesis of a 16α-(bromoalkylamide) derivative of estradiol (N-butyl, N-methyl, 11-[3′,17′ β-(dihydroxy)-1′,3′,5′ (10′)-estratrien-16′ α-yl]-9 (R/S)-bromo undecanamide) was performed by two different approaches starting from estrone. Each approach has the same key intermediate, containing an aldehyde group, but differs by the bromination step and the timing of formation of the amide group. This compound was found to cause, at 100 ·M, a complete inhibition of 17β-hydroxysteroid dehydrogenase (17β-HSD) responsible for the interconversion of estrone and estradiol. The corresponding IC50 value was 10.6 ·M. In the estrogen-sensitive ZR-75-1 human breast cancer cell line, this estradiol derivative has no estrogenic activity at 30 nM and only a minimal estrogenic activity (10% above the basal level) at l ·M. At this latter concentration, this compound causes a 28% inhibition of 0.1 nM E2-induced cell proliferation (antiestrogenic activity). Thus, the introduction of a side-chain with a secondary bromide and a butyl methyl amide group at the 16α-position of estradiol has two interesting effects; namely an inhibition of cytosolic 17β-HSD and a blockade of the estrogenic effect of estradiol. (Steroids 59:536-547, 1994).
- Pelletier, Joelle D.,Labrie, Fernand,Poirier, Donald
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- INFLUENCE OF THE CHEMICAL AND TEXTURAL PORPERTIES OF K2Cr2O7 SUPPORTED ON SOLIDS, IN THE OXIDATION OF CHOLESTEROL
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Several K2Cr2O7 supported reagents on inert solids have been obtained by deposition of K2Cr2O7 on different solids.AlPO, BPO and solid mixtures BPO-AlPO are used as supports.The K2Cr2O7 is deposited on solid as large crystals detected by an X-ray diagram in the Cr50 and Cr25 series giving solids with very low surface areas.The number of acid and oxidizing sites is determined.Solids supports with small surface areas and large pore diameter give K2Cr2O7 supported reagents with higher activity than those obtained from solids with high surface areas and large pores.
- Climent, M. S.,Marinas, J. M.,Sinisterra, J. V.
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- D-ring allyl derivatives of 17β- and 17α-estradiols: Chemical synthesis and 13C NMR data
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We report the 13 C NMR data for 17β-estradiol, 17α-estradiol, and a series of ten 17β- or 17α-estradiol derivatives bearing an allyl group on the D-ring (at C-17, C-16, and C-15 positions). The target 17β-OH estradiol derivatives were synthesized from estrone by well known obtained by a modified Mitsunoba alcohol inversion of the allyl group (17α, 17β, 16α, 16β, and 15β) and two alcohol stereochemistries (17β and 17α) of the D- ring were studied, resulting in an important source of data. The effect of allyl-positioning and alcohol stereochemistry on 13C NMR chemical shifts was also identified, producing important points of comparison for other steriod analogs.
- Dionne, Patricia,Ngatcha, Beatrice Tchedam,Poirier, Donald
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- An improved synthesis of nomegestrol acetate
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Oral contraceptives (OCs) are synthetic steroids, or progestins, which are structurally related to testosterone or to progesterone. Many progestins have been synthesized and approved for OCs, hormonal replacement therapy (HRT), or the treatment of some gynecological disorders. Nomegestrol acetate (NOMAc) is a newly approved OC and has gained rapid acceptance in many countries for OC or HRT. The synthesis of NOMAc remains challenging and costly. We have developed a novel and improved procedure for the synthesis of NOMAc with a total of 11 steps and an overall good yield without the use of hazardous reagents.
- Lu, He-Lin,Wu, Zong-Wen,Song, Shu-Yong,Liao, Xiao-Dan,Zhu, Yan,Huang, Yun-Sheng
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- E-Ring extended estrone derivatives: introduction of 2-phenylcyclopentenone to the estrone D-ring via an intermolecular Pauson-Khand reaction
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An expedient synthetic route to E-ring extended estrone derivatives is reported. Estrone-derived cyclopentenones were accessed by an intermolecular Pauson-Khand (PK) cycloaddition. It was found that electron donating and withdrawing substituents in the arylalkyne increased and decreased the yields of PK products, respectively. The stereochemistry of the products was elucidated by X-ray and NMR studies.
- Kaasalainen, Emmi,Tois, Jan,Russo, Luca,Rissanen, Kari,Helaja, Juho
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- A concise stereocontrolled total synthesis of (+)-estrone
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(+)-Estrone (1) has been synthesized in diastereo- and regioselective manners in six steps in 28% overall yield (38% based on the consumed material) starting from (-)-dicyclopentadienone (2) by employing a Diels-Alder cycloaddition-cycloreversion as the key step.
- Takano,Moriya,Ogasawara
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- Copper bromide mediated A-ring dehydrogenation of 19-norsteroids
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A dehydrogenation reaction applied to 19-norsteroids 1a or 1b, with copper(II) bromide in different alcohols yielded estrone alkyl ethers or 13β-ethyl-3-alkoxy gonanes along with products in which the steroid 6-position has been oxidized as aell. Use of small amounts of trialkyl orthoformates in the reaction considerably diminished the overoxidized products.
- Brito,Campos,Salgado-Zamora,Fabbro
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- Enantioconvergent synthesis of (+)-estrone from racemic 4-tert-butoxy-2-cyclopentenone
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(+)-Estrone has been synthesized in an enantioconvergent manner from racemic 4-tert-butoxy-2-cyclopentenone via contrasteric Diels-Alder reaction and lipase-mediated kinetic transesterification as the key steps.
- Sugahara, Tsutomu,Ogasawara, Kunio
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- Synthesis of 17-dihydroisoxazolyl steroids of the androstane and estrone series
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1,3-Dipolar cycloaddition of nitrile oxides to 17β-hydroxy-17α-vinyl steroids of the estrone series proceeds both regio- and stereoselectively. The stereoselectivity of the process decreases in going to steroids of the androstane series. The major epimer has S configuration of the new chiral center.
- Litvinovskaya,Drach,Lapchinskaya,Khripach
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- Structure - Activity relationship of Aza-steroids as PI-PLC inhibitors
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A number of aza-steroids were synthesized as potent phosphatidylinositol phospholipase C (PI-PLC) inhibitors. The epimeric mixtures 22,25-diazacholesterol (8a) and 3β-hydroxy-22,25-diazacholestane (8b) were among the most active of these inhibitors, with IC50 values of 7.4 and 7.5 μM, respectively. The 20α epimer, 8a2 (IC50 = 0.64 μM), whose stereochemistry at C-20 coincides with that of cholesterol, was found 50 times more potent than the 20β epimer, 8a1 (IC50 = 32.2 μM). In diaza-estrone derivatives, the 3-methoxy group on the aromatic A-ring of 23 exhibited moderate PI-PLC inhibitory activity (IC50 = 19.7 μM), while compound with a free hydroxyl group (21) was inactive. However, in diaza-pregnane derivatives, epimers with a 3-hydroxyl group (8a, IC50 = 7.4 μM) exhibited more potent PI-PLC inhibitory activity than their counterparts with 3-methoxyl group on the non-aromatic A-ring (26, IC50 = 17.4 μM). We have illustrated in our previous publication that 3-hydroxyl-6-aza steroids are potent PI-PLC inhibitors. However, simultaneous presence of the 6-aza and 22,25-diaza moieties in one molecule as in 13, led to loss of activity. Epimeric mixture 8a showed selective growth inhibition effects in the NCI in vitro tumor cell screen with a mean GI50 value (MG-MID) of 5.75 μM for 54 tumors.
- Xie, Wenge,Peng, Hairuo,Kim, Deog-Il,Kunkel, Mark,Powis, Garth,Zalkow, Leon H.
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- Synthesis of novel estrone analogs by incorporation of thiophenols via conjugate addition to an enone side chain
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Functionalized estrogen analogs have received interest due to their unique and differing biological activity compared to their parent compounds. The synthesis of a new class of 3-methoxyestrone analogs functionalized at the C17 position possessing both alkyl and aryl substituted α,β-unsaturated ketones is described, along with their thiophenol conjugate addition products.
- Kopel, Lucas C.,Ahmed, Mahmoud S.,Halaweish, Fathi T.
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- Photocatalytic Generation of 2-Azolyl Radicals: Intermediates for the Azolylation of Arenes and Heteroarenes via C-H Functionalization
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The 2-azolyl radical, generated from 2-bromoazoles via photocatalysis, is a powerful intermediate for the intermolecular arylation of unmodified (hetero)arenes. The reaction is characterized by mild conditions, operational simplicity, tolerance toward functional and sterically demanding groups, broad scope, and anti-Minisci selectivity. A working mechanism is provided, and a low-solubility amine is essential for successful coupling. The utility of the reaction is demonstrated via late-stage functionalization of methyl estrone and application toward other bromoarenes.
- Arora, Amandeep,Weaver, Jimmie D.
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- Direct Synthesis of α-Amino Nitriles from Sulfonamides via Base-Mediated C-H Cyanation
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Herein, we disclose a transition-metal-free reaction system that enables α-cyanation of sulfonamides through C-H bond cleavage for the preparation of α-amino nitriles, including difficult-to-access all-alkyl α-tertiary scaffolds. More than 50 substrate examples prove a wide functional group tolerance. Additionally, its synthetic practicality is highlighted by gram-scalability and the late-stage modification of natural compounds. Mechanistic experiments suggest that this process involves in situ formation of an imine intermediate via base-promoted elimination of HF.
- Shi, Shasha,Yang, Xianyu,Tang, Man,Hu, Jiefeng,Loh, Teck-Peng
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p. 4018 - 4022
(2021/05/26)
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- A Metal-Free Direct Arene C?H Amination
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The synthesis of aryl amines via the formation of a C?N bond is an essential tool for the preparation of functional materials, active pharmaceutical ingredients and bioactive products. Usually, this chemical connection is only possible by transition metal-catalyzed reactions, photochemistry or electrochemistry. Here, we report a metal-free arene C?H amination using hydroxylamine derivatives under benign conditions. A charge transfer interaction between the aminating reagents TsONHR and the arene substrates enables the chemoselective amination of the arene, even in the presence of various functional groups. Oxygen was crucial for an effective conversion and its accelerating role for the electron transfer step was proven experimentally. In addition, this was rationalized by a theoretical study which indicated the involvement of a dioxygen-bridged complex with a “Sandwich-like” arrangement of the aromatic starting materials and the aminating agents at the dioxygen molecule. (Figure presented.).
- Wang, Tao,Hoffmann, Marvin,Dreuw, Andreas,Hasagi?, Edina,Hu, Chao,Stein, Philipp M.,Witzel, Sina,Shi, Hongwei,Yang, Yangyang,Rudolph, Matthias,Stuck, Fabian,Rominger, Frank,Kerscher, Marion,Comba, Peter,Hashmi, A. Stephen K.
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supporting information
p. 2783 - 2795
(2021/04/05)
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- Site-Specific Oxidation of (sp3)C-C(sp3)/H Bonds by NaNO2/HCl
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A site-specific oxidation of (sp3)C-C(sp3) and (sp3)C-H bonds in aryl alkanes by the use of NaNO2/HCl was explored. The method is chemical-oxidant-free, transition-metal-free, uses water as the solvent, and proceeds under mild conditions, making it valuable and attractive to synthetic organic chemistry.
- Zhao, Jianyou,Shen, Tong,Sun, Zhihui,Wang, Nengyong,Yang, Le,Wu, Jintao,You, Huichao,Liu, Zhong-Quan
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supporting information
p. 4057 - 4061
(2021/05/26)
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- Trialkylammonium salt degradation: Implications for methylation and cross-coupling
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Trialkylammonium (most notably N,N,N-trimethylanilinium) salts are known to display dual reactivity through both the aryl group and the N-methyl groups. These salts have thus been widely applied in cross-coupling, aryl etherification, fluorine radiolabelling, phase-transfer catalysis, supramolecular recognition, polymer design, and (more recently) methylation. However, their application as electrophilic methylating reagents remains somewhat underexplored, and an understanding of their arylation versus methylation reactivities is lacking. This study presents a mechanistic degradation analysis of N,N,N-trimethylanilinium salts and highlights the implications for synthetic applications of this important class of salts. Kinetic degradation studies, in both solid and solution phases, have delivered insights into the physical and chemical parameters affecting anilinium salt stability. 1H NMR kinetic analysis of salt degradation has evidenced thermal degradation to methyl iodide and the parent aniline, consistent with a closed-shell SN2-centred degradative pathway, and methyl iodide being the key reactive species in applied methylation procedures. Furthermore, the effect of halide and non-nucleophilic counterions on salt degradation has been investigated, along with deuterium isotope and solvent effects. New mechanistic insights have enabled the investigation of the use of trimethylanilinium salts in O-methylation and in improved cross-coupling strategies. Finally, detailed computational studies have helped highlight limitations in the current state-of-the-art of solvation modelling of reaction in which the bulk medium undergoes experimentally observable changes over the reaction timecourse. This journal is
- Assante, Michele,Baillie, Sharon E.,Juba, Vanessa,Leach, Andrew G.,McKinney, David,Reid, Marc,Washington, Jack B.,Yan, Chunhui
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p. 6949 - 6963
(2021/06/02)
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- Ruthenium-Catalyzed Dehydrogenation of Alcohols with Carbodiimide via a Hydrogen Transfer Mechanism
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Ruthenium-catalyzed oxidative dehydrogenation of alcohols using carbodiimide as an efficient hydrogen acceptor has been developed. The protocol exhibits wide substrate scope with good to excellent yields. The results of the kinetic analysis indicated that the reaction mechanism includes the hydrogen transfer process and that the addition of carbodiimide is essential for the reaction system, and the resulting amidine also could react as a hydrogen acceptor.
- Sueki, Shunsuke,Matsuyama, Mizuki,Watanabe, Azumi,Kanemaki, Arata,Katakawa, Kazuaki,Anada, Masahiro
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p. 4878 - 4885
(2020/06/02)
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- Design, synthesis and anti-tumor evaluation of novel steroidal glycoconjugate with furoxan derivatives
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In this study, eighteen novel steroidal-furoxan derivatives with 3-glycosyl or 3-methoxy moiety (12a-c, 13a-c, 17a-c, 26a-c, 27a-c and 28a-c) were synthesized and their anti-proliferative activity was evaluated against eight drug-sensitive and three drug-resistant cancer cell lines HeLa, A2780, LNCaP, PC-3, MDA-MB-231, MCF-7, SW480, A549, MCF-7/ADR, A2780/CDDP and A2780/T. Most of them displayed significant anti-cancer potency in vitro with IC50 values at the nanomole level. Among them, 3-methoxy steroidal-furoxan hybrids expressed much better activity than that of 3-glycosyl substitute ones, while estrane and 5α-H-androstane scaffold were slightly more favorable to the improvement of anti-proliferative activity. Especially, compounds 27c and 28b showed the strongest cytotoxicity with IC50 values of 0.0007–0.034 and 0.0011–0.008 μM, respectively in five drug-sensitive cancer cell lines. Furthermore, 3-glycoconjugates 13a, 13c, 17b and 3-methoxy compounds 27a, 27c, 28b displayed lower toxicity in nontumorigenesis cells HOSEC and expressed a good selectivity against malignant cells in vitro. Preliminary study of pharmacology showed that the introduction of glucose at 3-position in steroidal core seems unable to use glucose transporters to improve the selectivity against proliferation of malignant cells, while the NO-releasing capacity might explain the potent anti-neoplastic activity of these compounds. And compound 28b could induce the apoptosis and hardly affected the cell cycle of A2780. Then, the further study of these steroidal-furoxan hybrids merits to explore and develop a desirable anti-cancer candidate.
- Li, Haihong,Wang, Ke,Wan, Qi,Chen, Ying
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- Oxidation of secondary alcohols using solid-supported hypervalent iodine catalysts
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It is shown how secondary alcohols are oxidized to provide the corresponding ketones by use of Oxone and solid-supported hypervalent iodine catalysts. Under experimentally simple conditions with acetonitrile at elevated temperatures, excellent conversions were achieved with low catalyst loadings (0.2-5 mol%) when employing the conjugates 5 and 6 derived from IBX and IBS. The catalysts are broadly applicable to a range of alcohol substrates. Of primary importance with respect to sustainability issues, the metal-free catalysts are easily removed from the reaction mixture through filtration, and they can be re-used in oxidation processes for multiple times, without loss of catalytic activity.
- Ballaschk, Frederic,Kirsch, Stefan F.
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supporting information
p. 5896 - 5903
(2019/11/11)
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- Controllable Intramolecular Unactivated C(sp3)-H Amination and Oxygenation of Carbamates
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Dual catalyst-controlled intramolecular unactivated C(sp3)-H amination and oxygenation of carbamates merging visible-light photocatalysis and earth-abundant transition metal catalysis have been reported. Useful amino alcohol and diol derivatives could be selectively obtained from readily available tertiary alcohol derivatives. The possible mechanisms have been proposed via a 1,5-HAT process followed by Lewis acid-controlled cyclization. The nickel and zinc catalysts inhibit the formation of oxygenation and amination products, respectively. An interesting phenomenon of chirality transfer is also observed.
- Guo, Qihang,Ren, Xiang,Lu, Zhan
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supporting information
p. 880 - 884
(2019/05/16)
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- Rhodium-Catalyzed 1,1-Hydroacylation of Thioacyl Carbenes with Alkynyl Aldehydes and Subsequent Cyclization
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A rhodium-catalyzed 1,1-hydroacylation of thioacyl carbenes with alkynyl and alkenyl aldehydes and subsequent 6-endo-trig/dig cyclization are realized, giving structurally diverse 4H-thiopyran-4-ones and 2,3-dihydro-4H-thiopyran-4-ones in moderate to good yields. The oxidative addition of Rh(I) to aldehydes is proposed to be the turnover-limiting step. Manipulations of estrones demonstrate the applications of our formal (3 + 3) transannulations in the structural modifications of natural products.
- Zhou, Bingnan,Wu, Qiuyue,Dong, Ziyang,Xu, Jiaxi,Yang, Zhanhui
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supporting information
p. 3594 - 3599
(2019/05/24)
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- Photo-Fries Rearrangement of Some 3-Acylestrones in Homogeneous Media: Preparative and Mechanistic Studies
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Irradiation of a series of 3-acylestrones under a nitrogen atmosphere in cyclohexane, acetonitrile (MeCN), and methanol (MeOH) was investigated under steady-state conditions. The molecules underwent the photo-Fries rearrangement, with concomitant homolytic fragmentation of the ester group and [1;3]-acyl migration. This pathway afforded the ortho-acyl estrone derivatives, the main photoproducts, together with estrone. During the irradiation of 3-benzoyl estrone, epimerization of estrone through the Norrish type I reaction occurred, providing lumiestrone as the photoproduct. This photoreaction involves the fragmentation of the C-α at the carbonyl group (C-17) of the steroid. On the other hand, epimerization of ortho-regioisomer 2-acetyl estrone occurred during the irradiation of 3-acetyl estrone. Photosensitization with acetone and chemical quenching with N,N,N,N-tetramethyldiazetinedioxide of the photo-Fries reaction confirmed that the photoreaction took place from the singlet excited state while the Norrish type I reaction proceeds efficiently from the triplet excited state. Solvent effects, as well as the nature of the acyl group on the photoreactions, were also studied.
- Quindt, Matías I.,Gola, Gabriel F.,Ramirez, Javier A.,Bonesi, Sergio M.
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p. 7051 - 7065
(2019/06/18)
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- Silver(I)-Catalyzed Widely Applicable Aerobic 1,2-Diol Oxidative Cleavage
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The oxidative cleavage of 1,2-diols is a fundamental organic transformation. The stoichiometric oxidants that are still predominantly used for such oxidative cleavage, such as H5IO6, Pb(OAc)4, and KMnO4, generate stoichiometric hazardous waste. Herein, we describe a widely applicable and highly selective silver(I)-catalyzed oxidative cleavage of 1,2-diols that consumes atmospheric oxygen as the sole oxidant, thus serving as a potentially greener alternative to the classical transformations.
- Zhou, Zhong-Zhen,Liu, Mingxin,Lv, Leiyang,Li, Chao-Jun
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p. 2616 - 2620
(2018/02/13)
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- Targeting RORs nuclear receptors by novel synthetic steroidal inverse agonists for autoimmune disorders
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Designing novel inverse agonists of NR RORγt still represents a challenge for the pharmaceutical community to develop therapeutics for treating immune diseases. By exploring the structure of NRs natural ligands, the representative arotenoid ligands and RORs specific ligands share some chemical homologies which can be exploited to design a novel molecular structure characterized by a polycyclic core bearing a polar head and a hydrophobic tail. Compound MG 2778 (8), a cyclopenta[a]phenantrene derivative, was identified as lead compound which was chemically modified at position 2 in order to obtain a small library for preliminary SARs. Cell viability and estrogenic activity of compounds 7, 8, 19a, 30, 31 and 32 were evaluated to attest selectivity. The selected 7, 8, 19a and 31 compounds were assayed in a Gal4 UAS-Luc co-transfection system in order to determine their ability to modulate RORγt activity in a cellular environment. They were evaluated as inverse agonists taken ursolic acid as reference compound. The potency of compounds was lower than that of ursolic acid, but their efficacy was similar. Compound 19a was the most active, significantly reducing RORγt activity at low micromolar concentrations.
- Dal Prà, Matteo,Carta, Davide,Szabadkai, Gyorgy,Suman, Matteo,Frión-Herrera, Yahima,Paccagnella, Nicola,Castellani, Giulia,De Martin, Sara,Ferlin, Maria Grazia
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p. 1686 - 1704
(2018/02/26)
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- Design, synthesis, and biological evaluation of steroidal analogs as estrogenic/anti-estrogenic agents
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Series of estrone based analogs were synthetically investigated at positions C-9, C-11, C-16, and C-17 positions, to be biologically evaluated via assessment of cell proliferation, cytotoxicity, and estrogenic/anti-estrogenic activity. LA-7 and LA-10 revealed their potential to exhibit inhibitory estrogenic profile. This was further validated by Estrogen Receptor-α (ER-α) and Estrogen Receptor-β (ER-β) competitive binding assays to reveal the high selective affinity of LA-7 towards ER-α at 5.49 μM, while LA-10 did not show any binding affinity towards neither ER-α nor ER-β; suggesting another mechanism for inhibition. This was validated by in silico molecular docking simulations of LA-7 to reveal the optimum binding affinity of LA-7 towards ER-α.
- Alsayari, Abdulrhman,Kopel, Lucas,Ahmed, Mahmoud Salama,Pay, Adam,Carlson, Taylor,Halaweish, Fathi T.
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- Synthesis of 2,2,2,-Trichloroethyl Aryl- and Vinyldiazoacetates by Palladium-Catalyzed Cross-Coupling
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An efficient and convenient synthesis of 2,2,2-trichloroethyl (TCE) aryl- and vinyldiazoacetates was achieved by palladium-catalyzed cross-coupling reactions between TCE diazoacetates and aryl or vinyl iodides. The broad substrate scope allows for rapid and facile formation of TCE aryl- and vinyldiazoacetates, which recently have emerged as versatile reagents for rhodium-carbene chemistry.
- Fu, Liangbing,Mighion, Jeffrey D.,Voight, Eric A.,Davies, Huw M. L.
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supporting information
p. 3272 - 3275
(2017/03/16)
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- Preparation 19-nor -5 (10)-androstene ketone compound method
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The invention discloses a method for preparing a 19-Norandrost-5(10)-ene-3,17-dione compound. The method comprises the steps of by taking estrone as an ingredient, firstly sequentially performing etherification reaction, ketal protection reaction and birch reduction reaction to obtain a birch reduction product; then by taking lower fatty acid as a catalyst, performing selective hydrolysis reaction on the birch reduction product to produce the 19-Norandrost-5(10)-ene-3,17-dione compound. According to the method, the hydrolysis technology of the birch reduction product containing 17-bit ketal protecting group is optimized and improved, and the single 19-Norandrost-5(10)-ene-3,17-dione with high yield and high selectivity can be obtained through selective hydrolysis reaction by taking binary fatty acid as an acid catalyst for the first time; in addition, the fact that the 17-bit ketal protecting derivatives of the single 19-Norandrost-5(10)-ene-3,17-dione compound can be obtained by taking lower unitary fatty acid as a catalyst is found for the first time.
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Paragraph 0072; 0073
(2017/01/12)
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- Structural analysis and biomedical potential of novel salicyloyloxy estrane derivatives synthesized by microwave irradiation
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New estrane salicyloyloxy or D-homo derivatives were synthesized under microwave (MW) or conventional heating from estrane precursors and methyl salicylate. The MW technique provides advantages regarding product yield and reaction time, and represents a more environmentally friendly approach than conventional heating. Considering the biomedical potential of estrane compounds, we evaluated the antioxidant activity and cytotoxicity of synthesized estrane derivatives in a series of in vitro tests, as well as their 3β-hydroxysteroid dehydrogenase/Δ5 → Δ4 isomerase (3βHSD) and 17β-hydroxysteroid dehydrogenase types 1, 2 and 3 (17βHSD1, 17βHSD2 and 17βHSD3) inhibition potentials. In DPPH tests, 3-methoxyestra-1,3,5(10)-trien-17β-yl salicylate displayed antioxidant potential, while all compounds exhibited OH radical neutralization activity. 3-Oxoestr-4-en-17β-yl salicylate showed strong cytotoxicity against MDA-MB-231 breast cancer cells, while 17-oxoestra-1,3,5(10)-trien-3-yl salicylate, estra-1,3,5(10)-triene-3,17β-diyl 3-benzoate 17-salicylate and 3-benzyloxy-17-salicyloyloxy-16,17-secoestra-1,3,5(10)-triene-16-nitrile showed the strongest inhibition of PC-3 prostate cancer cell growth. 3-Hydroxyestra-1,3,5(10)-trien-17β-yl salicylate was the best inhibitor of 17βHSD2, suggesting potential use in treating pathological conditions associated with estrogen depletion. For 3-methoxyestra-1,3,5(10)-trien-17β-yl salicylate and 3-oxoestr-4-en-17β-yl salicylate, X-ray crystal structure analysis and molecular energy optimization were performed to define their conformations and energy minima. Very good overlap in the region of the steroidal nucleus was observed for the molecular structures of each analyzed molecule in the crystalline state and after energy optimization, while conformer analysis indicates conformational flexibility in the form of rotation around the C17···O2 bond. Structural geometry analysis for these compounds shows that the region of ring A in steroids, and especially the C3 atom functional group, is important structural features concerning antiproliferative activity against MDA-MB-231 cells.
- Klisuri, Olivera R.,Szcsi, Mihly,Djurendi, Evgenija A.,Nikoletta, Szab,Herman, Bianka Edina,Jovanovi anta, Suzana S.,Dojinovi Vujakovi, Sanja V.,Nikoli, Andrea R.,Pavlovi, Ksenija J.,Ajdukovi, Jovana J.,Okljea, Aleksandar M.,Petri, Edward T.,Koji, Vesna V.,Saka, Marija N.,Penov Gai, Katarina M.
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p. 947 - 960
(2016/05/10)
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- Eco-friendly synthesis of 3-etherified estrones
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The conventional etherification uses toxic or hardly degradable alkylating agents. An eco-friendly tandem etherification/aromatization is presented to prepare estrone 3-secondary ethers from easily available dienone 1. Three marketed 3-etherified estrogen drugs were synthesized with the method from commercial available starting material.
- Zheng, Dong-Qing,Jing, Yu,Zheng, Bing-Ying,Ye, Yun-Fei,Xu, Sheng,Tian, Wei-Sheng,Ma, Hai-Yan,Ding, Kai
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p. 2164 - 2169
(2016/04/09)
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- CORTISTATIN ANALOGUES, SYNTHESES, AND USES THEREOF
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New cortistatin compounds and pharmaceutically acceptable salts and pharmaceutically acceptable compositions thereof are provided. These compounds can be used to treat a disorder mediated by CDK8 and/or CDK19 kinase or by the Mediator Complex generally. In particular, the compounds can be used, for example, to treat a disorder such as a tumor, cancer, or a disorder associated with angiogenesis.
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Paragraph 00408
(2016/11/28)
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- Chemo-, regio-, and stereo-selective perfluoroalkylations by a Grignard complex with zirconocene
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The synthesis of highly reactive perfluoroalkyl Grignard reagents with early transition metal zirconocene complexes and their new types of highly chemo-, regio-, and stereo-selective perfluoroalkylation reactions are reported with epoxides in particular. The zirconocene complex is advantageous in activating the perfluoroalkyl Grignard species. The zirconocene·Grignard complexes were clarified by DOSY. Both 1H and 19F DOSY analyses show that the addition of MAO and dioxane to the mixture of RFMgCl and Cp2ZrCl2 connects Cp2Zr and RFMg to generate the zirconocene/perfluoroalkyl-Grignard/dioxane complex.
- Fujiu, Motohiro,Negishi, Kazuyuki,Guang, Jie,Williard, Paul G.,Kuroki, Shigeki,Mikami, Koichi
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supporting information
p. 19464 - 19468
(2015/11/27)
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- CORTISTATIN ANALOGUES AND SYNTHESES AND USES THEREOF
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Provided herein are compounds of Formula (A), (B), (C), (D) and (E), pharmaceutically acceptable salts, quaternary amine salts, and N-oxides thereof, and pharmaceutical compositions thereof. Compounds of Formula (A), (B), (C), (D), and (E) are contemplated useful as therapeutics for treating a wide variety of conditions, e.g., including but not limited to, conditions associated with angiogenesis and with CDK8 and/or CDK19 kinase activity. Further provided are methods of inhibiting CDK8 and/or CDK19 kinase activity, methods of modulating the β-catenin pathway, methods of modulating STAT1 activity, methods of modulating the TGFβ/BMP pathway, methods of modulating HIF-1 -alpha activity in a cell, and methods of increasing BIM expression to induce apoptosis, using a compound of Formula (A), (B), (C), (D), or (E). Further provided are CDK8 and CDK19 point mutants and methods of use thereof.
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Paragraph 00382
(2015/07/15)
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- Copper catalyzed Heck-like cyclizations of oxime esters
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Copper catalyzed Heck-like cyclizations of oxime esters are described. Mechanistic studies indicate a reaction pathway that proceeds via the generation and cyclization of an intermediate that possesses iminyl radical character. To the best of our knowledge, this work encompasses the first examples of Cu-catalyzed aza-Heck reactions that proceed via oxidative initiation at nitrogen to generate products containing a new alkene. This new protocol is also an effective alternative to Pd-based systems and highlights the value of replacing precious metal catalysts with cheaper and more sustainable variants. This journal is the Partner Organisations 2014.
- Faulkner, Adele,Race, Nicholas J.,Scott, James S.,Bower, John F.
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p. 2416 - 2421
(2014/05/20)
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- Catalytic asymmetric torgov cyclization: A concise total synthesis of (+)-estrone
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An asymmetric Torgov cyclization, catalyzed by a novel, highly Bronsted acidic dinitro-substituted disulfonimide, is described. The reaction delivers the Torgov diene and various analogues with excellent yields and enantioselectivity. This method was applied in a very short synthesis of (+)-estrone.
- Prevost, Sebastien,Dupre, Nathalie,Leutzsch, Markus,Wang, Qinggang,Wakchaure, Vijay,List, Benjamin
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supporting information
p. 8770 - 8773
(2014/08/18)
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- An easy stereoselective synthesis of 5(10)-estrene-3β,17α-diol, a biological marker of pregnancy in the mare
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5(10)-Estrene-3β,17α-diol is an essential reference material for doping analysis in horse-racing laboratories. It is used to detect misuse, for doping purpose, of the pregnancy status in the mare. Its stereoselective synthesis from 17β-estradiol-3-methyl ether (prepared from estrone or 17β-estradiol) was performed in four steps: (1) Mitsunobu inversion of the 17β-alcohol; (2) Birch reduction of the aromatic ring; (3) stereoselective reduction of the 3-ketone via Noyori asymmetric transfer hydrogenation; (4) chemoenzymatic purification.
- Balssa, Frédéric,Fischer, Michael,Bonnaire, Yves
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- Amphidynamic crystals of a steroidal bicyclo[2.2.2]octane rotor: A high symmetry group that rotates faster than smaller methyl and methoxy groups
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The synthesis, crystallization, single crystal X-ray structure, and solid state dynamics of molecular rotor 3 provided with a high symmetry order and relatively cylindrical bicyclo[2.2.2]octane (BCO) rotator linked to mestranol fragments were investigated in this work. By use of solid state 13C NMR, three rotating fragments were identified within the molecule: the BCO, the C19 methoxy and the C18 methyl groups. To determine the dynamics of the BCO group in crystals of 3 by variable temperature 1H spin-lattice relaxation (VT 1H T1), we determined the 1H T1 contributions from the methoxy group C19 by carrying out measurements with the methoxy-deuterated isotopologue rotor 3-d6. The contributions from the quaternary methyl group C18 were estimated by considering the differences between the VT 1H T1 of mestranol 8 and methoxy-deuterated mestranol 8-d3. From these studies it was determined that the BCO rotator in 3 has an activation energy of only 1.15 kcal mol-1, with a barrier for site exchange that is smaller than those of methyl (Ea = 1.35 kcal mol-1) and methoxy groups (Ea = 1.92 kcal mol-1), despite their smaller moments of inertia and surface areas.
- Rodriguez-Molina, Braulio,Perez-Estrada, Salvador,Garcia-Garibay, Miguel A.
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supporting information
p. 10388 - 10395
(2013/08/23)
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- Pyridinium o-iodoxybenzoate as a safe form of a famous oxidant
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The stable pyridinium salt of o-iodoxybenzoic acid (PIBX) that is easy to obtain can serve as a convenient substitute of IBX as an oxidant. PIBX is safer, has neutral properties behaves as an equivalent to IBX in the oxidation of alcohols to ketones or aldehydes in polar solvents (DMF, DMSO), and provides higher oxidation rate in THF due to better solubility.
- Kumanyaev, Ivan M.,Lapitskaya, Margarita A.,Vasiljeva, Ljudmila L.,Pivnitsky, Kasimir K.
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experimental part
p. 129 - 131
(2012/09/05)
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- Synthesis of estradiol-cinnamide conjugates
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The synthesis of a number of structurally related estradiol-17α- ylmethyl hydroxycinnamides and of one novel estra- 1,3,5(10),6-tetraen-3-ol- 17β-yl hydroxycinnamide is described, using a microwave assisted amidation of steroidal amines with pentafluorophenol activated, non-protected hydroxycinnamic acids as a key step. A selection of the compounds and of other estra-1,3,5(10)-trien-3-ol 17β-yl hydroxycinnamides was screened against 60 human cancer cell lines, derived from nine neoplastic diseases. From the overall results of the screening, it could be inferred that dihydroxycinnamide derived estradiol conjugates exhibit a better cytotoxic profile when compared with hydroxymethoxycinnamide derived estradiol conjugates.
- Morais, Goreti Ribeiro,Thiemann, Thies
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p. 549 - 554
(2012/11/13)
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- A simple and convenient synthesis of 2-methoxyestradiol from estrone
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A simple and straightforward synthesis of 2-methoxyestradiol have been achieved in nine synthetic steps with 21% of overall yield. Being a convenient process, it can be upscaled to industrial process.
- Prakasham,Shanker, Karuna,Negi, Arvind S.
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scheme or table
p. 467 - 470
(2012/05/19)
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- Protecting group effect on the 1,2-dehydrogenation of 19-hydroxysteroids: a highly efficient protocol for the synthesis of estrogens
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19-O-Acylation was found to be indispensable for 1,2-dehydrogenation of 19-hydroxyandrost-4-ene-3,17-dione 1a with DDQ as an oxidant after exploring a variety of C-19 substituents. 1,2-Dehydrogenation in combination with subsequent A-ring aromatization via retro-aldol reaction provided a flexible and efficient protocol for the synthesis of estrogens. To demonstrate the utility of the protocol, pharmaceutically attractive estrogens were synthesized from easily available 19-hydroxy-4-ene-3-keto steroids.
- Jing, Yu,Xu, Cheng-Gong,Ding, Kai,Lin, Jing-Rong,Jin, Rong-Hua,Tian, Wei-Sheng
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scheme or table
p. 3242 - 3245
(2010/08/19)
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- Enantioselective synthesis of (+)-estrone exploiting a hydrogen bond-promoted Diels?Alder reaction
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Starting from Danes diene and methylcyclopentenedione, (+)-estrone is synthesized along the Quinkert?Dane route in 24% total yield. The key step is an enantioselective Diels?Alder reaction promoted by an amidinium catalyst as efficiently as by a traditional Ti-TADDOLate Lewis acid.
- Weimar, Marko,Duerner, Gerd,Bats, Jan W.,Goebel, Michael W.
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supporting information; experimental part
p. 2718 - 2721
(2010/07/17)
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- A novel, versatile D→BCD steroid construction strategy, iIIustrated by the enantioselective total synthesis of estrone
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Chemical Equation presented A general steroid synthesis Is presented that relies on prior formation of three stereogenlc centers (C8, C13, and C14) on a D ring template, followed by C- and B-ring cyclizatlons. The assembly of the key D ring template, achieved by a 3-component conjugate addition/alkylation process, allows Introduction of structural variety as required. The method Is illustrated by the total synthesis of estrone via a C-ring closing metathesis and a B-ring Heck cyclization.
- Foucher, Vincent,Gulzzardi, Benedetta,Groen, Marinus B.,Light, Mark,Linclau, Bruno
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supporting information; experimental part
p. 680 - 683
(2010/04/02)
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- Stereoselective synthesis of some methyl-substituted steroid hormones and their in vitro cytotoxic activity against human gastric cancer cell line MGC-803
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A series of 3-, 7-, 15-, and 16-methyl-substituted steroid analogs were synthesized via a highly stereoselective 1,6-conjugate addition. Under the catalysis of CuBr, AlMe3 reacted with four steroid dienone precursors to afford either the corresponding α-epimer of C-3 and C-7 methyl-substituted steroids as the major products, and the ratio of α/β was up to 10/1. No β-epimer has been detected for methyl addition at C-16. However, under the same reaction conditions, enantioselective methyl addition at C-15 afforded the 15β-epimer as the major product. The preliminary SAR analysis showed that the methyl substituents at C-7α and C-15β positions lead to a dramatical increase in potency against human gastric cancer cell line MGC-803.
- Li, Chun,Qiu, Wenwei,Yang, Zhengfeng,Luo, Jian,Yang, Fan,Liu, Mingyao,Xie, Juan,Tang, Jie
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experimental part
p. 859 - 869
(2010/10/18)
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- Two versatile and parallel approaches to highly symmetrical open and closed natural product-based structures
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Two parallel approaches for preparing diverse and highly symmetrical homohybrids derived from a series of mono- and diterpenes, steroids, and alkaloids are reported. Both procedures are based on the mono-addition of bis(alkynyl) dilithium reagents to natural products having a carbonyl group to produce the corresponding al-kynyl derivatives. The Glaser-Hay Cu-promoted homocoupling of these al-kynyl natural product mono-adducts as well as the Huisgen Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction resulted in the synthesis of ste-roid-, terpene-, and alkaloid-based ho-mohybrid derivatives incorporating di-verse spacers to join the natural product scaffolds. Straightforward entries to novel closed highly symmetrical and complex estrone-based macrocyclic and cage architectures by means of the Glaser-Eglinton homocoupling and the CuAAC reaction have been devised.
- Montenegro, Hector E.,Ramirez-Lopez, Pedro,De La Torre, Maria C.,Asenjo, Maria,Sierra, Miguel A.
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supporting information; experimental part
p. 3798 - 3814
(2010/07/05)
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- Estrano[17,16-e]pyrimidine-amino acid and estrano[17,16-e]pyrimidinepeptide conjugates
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Estrone has been converted to an aminopyrimidino [17,16-e]-annelated estrane derivative. A number of amino acids dipeptides and tripeptides have been linked to the aminopyrimidino unit of the annelated steroid. The tripeptide motifs may be used for the complexation of metals, such as of technetium as a radio label for the potential detection of estrogen positive breast cancer cells.
- Matsumoto, Tomohiro,Shiine, Kodai,Mataka, Shuntaro,Thiemanna, Thies
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experimental part
p. 391 - 396
(2009/12/25)
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- Microwave-assisted methylation of phenols with tetramethylammonium chloride in the presence of K2CO3 or Cs2CO3
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We have evaluated the potential of using tetramethylammonium chloride (Me4NCl) as an alternative methylating agent for phenols under microwave-assisted conditions. Its chemical behavior was tested in a reaction with 2-naphthol in the presence of various bases and solvents. The method was then applied in 1,2-dimethoxyethane or toluene under heterogeneous conditions for the O-methylation of a series of phenolic compounds. We found that many simple phenols can be methylated in the presence of K2CO3, whereas some other less-reactive phenols require the presence of the more reactive Cs2CO3.
- Mara?, Nenad,Polanc, Slovenko,Ko?evar, Marijan
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experimental part
p. 11618 - 11624
(2009/04/05)
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- o-Iodoxybenzoic acid in dimethylformamide as a convenient reagent for the oxidation of alcohols to aldehydes and ketones
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DMF dissolves o-iodoxybenzoic acid (up to 0.1 mol dm-3) and, therefore, is a solvent of choice for the reactions with o-iodoxybenzoic acid simplifying significantly a product isolation procedure due to a higher volatility. The reaction rate and selectivity of the oxidation of alcohols to corresponding carbonyl compounds with o-iodoxybenzoic acid in DMF are close to those in DMSO.
- Lapitskaya, Margarita A.,Vasiljeva, Ljudmila L.,Pivnitsky, Kasimir K.
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scheme or table
p. 309 - 311
(2009/05/27)
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- 7α-Alkoxyestra-1,3,5(10)-trienes
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α-Alkoxyestradiols were prepared through LiAlH4 reduction of a suitably protected 6α,7α-epoxyestra-1,3,5(10)-trien-3-ol-17- one, alkylation of the resultant 7α-hydroxyestra-1,3,5(10)-trien-3-ol-17- one derivative and subsequent transformation of the C17 functionality.
- Yasuda, Takumi,Shima, Yuji,Ideta, Keiko,Das Neves Oliveira, Cristina,Thiemann, Thies
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- Formal total synthesis of (±)-estrone and zirconocene-promoted cyclization of 2-fluoro-1,7-octadienes and ru-catalyzed ring closing metathesis
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(Chemical Equation Presented) A new and diastereoselective method for the synthesis of the estrone skeleton from a substituted styrene based on sequential 3-fold use of Cp2ZrBu2 (oxidative addition-alkylation and two cyclization-alkylation sequences) and a ruthenium complex catalyzed RC-metathesis of a sterically hindered diene was developed. The prepared estratetraene was obtained in 7 steps from a commercially available starting material and thus the overall synthesis of estrone could be accomplished in 9 steps. Moreover, we have also found that the course of the reaction of substrates bearing the 2-halo-1,7-diene moiety with Cp2ZrBu 2, i.e., cyclization or oxidative addition to the C-X bond, could be controlled by the nature of the halogen leaving group.
- Herrmann, Pavel,Budesinsky, Milos,Kotora, Martin
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p. 6202 - 6206
(2008/12/22)
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- Synthesis of terpene and steroid dimers and trimers having cyclobutadienyl-Co and aromatic tethers
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(Chemical Equation Presented) The reaction of natural product derived propargylic alcohols with CpCo(CO)2 produces three new types of natural product hybrids having two or three terpene or steroid fragments. The tether joining the natural product subunits is built during the reaction. Type 1 hybrids have two terpene or steroid moieties joined by a CpCo-cyclobutadiene tether, with the two units disposed in a 1,2-arrangement (9, 14, 22). Type 2 hybrids have a Co-cyclopentadienone tether (10). Type 3 has three units of terpene or steroid joined to a benzene ring (11, 12, 15). An unusual Co-mediated β-carbon elimination pathway of propargylic alcohols leading to ketones (an unknown process in this chemistry) has been observed.
- Sierra, Miguel A.,Torres, M. Rosario,De La Torre, Maria C.,Alvaro, Elsa
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p. 4213 - 4219
(2008/02/05)
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- Conversion of Torgov's synthesis of estrone into a highly enantioselective and efficient process
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A very direct and efficient conversion of the achiral Torgov diketone into the natural form of O-methyl estrone is described. Copyright
- Yeung, Ying-Yeung,Chein, Rong-Jie,Corey
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p. 10346 - 10347
(2008/03/12)
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- Indole diterpene synthetic studies: Development of a second-generation synthetic strategy for (+)-nodulisporic acids A and B
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(Chemical Equation Presented) A second-generation strategy for construction of (+)-nodulisporic acids A and B based on the development of a new, effective modular indole synthesis exploiting a sequential Stille cross-coupling/Buchwald- Hartwig union/cyclization tactic is disclosed. This strategy evolved due to the considerable acid instability of the C(24) hydroxyl group observed in several advanced intermediates during our first-generation approach.
- Smith III, Amos B.,Kuerti, Laszlo,Davulcu, Akin H.,Young, Shin Cho,Ohmoto, Kazuyuki
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p. 4611 - 4620
(2008/02/07)
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- Synthesis of chalcone derivatives on steroidal framework and their anticancer activities
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Chalcone derivatives on estradiol framework have been synthesized. Some of the derivatives showed potent anticancer activity against some human cancer cell lines. Compounds 9 and 19 showed potent activity against MCF-7, a hormone dependent breast cancer cell line. Chalcone 7 was further modified to the corresponding indanone derivative (19) using the Nazarov reaction, which showed better activity than the parent compound against the MCF-7 breast cancer cell line. Active anticancer derivatives were also evaluated for osmotic hemolysis using the erythrocyte as a model system. It was observed that chalcone derivatives showing cytotoxicity against cancer cell lines did not affect the fragility of erythrocytes and hence may be considered as non-toxic to normal cells.
- Saxena, Hari Om,Faridi, Uzma,Kumar,Luqman, Suaib,Darokar,Shanker, Karuna,Chanotiya, Chandan S.,Gupta,Negi, Arvind S.
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p. 892 - 900
(2008/02/13)
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- A new modular indole synthesis. Construction of the highly strained CDEF parent tetracycle of nodulisporic acids A and B
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Construction of the highly strained CDEF parent tetracycle, a structural motif found only in the potent ectoparasiticidal agents (+)-nodulisporic acids A and B and related congeners, has been achieved via a new modular indole synthesis, exploiting a sequential Stille cross-coupling/Buchwald-Hartwig union/cyclization tactic. The new indole synthesis holds the promise of rapid assembly of diverse, highly substituted indoles possessing uncommon substitution patterns.
- Smith III, Amos B.,Kuerti, Laszlo,Davulcu, Akin H.
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p. 2167 - 2170
(2007/10/03)
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- A simple, convenient and chemoselective formylation of sterols by Vilsmeier reagent
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Vilsmeier reagent (DMF-POCl3) was used as an efficient formylating agent. Several sterols having sec-hydroxyl group at 3/17-position have been modified into respective formate esters. The method is simple, mild, chemoselective and provides sec-alcoholic protection in good yields.
- Srivastava, Vandana,Negi, Arvind Singh,Kumar,Gupta
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p. 632 - 638
(2007/10/03)
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- Combined epimerisation and acylation: Meerwein-ponndorf-verley-oppenauer catalysts in action
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A practical racemisation-epimerisation method for chiral secondary alcohols has been developed. Meerwein-Ponndorf-Verley-Oppenauer catalysts such as neodymium(III) isopropoxide are able to racemise these alcohols with retention of other stereocentres in the molecule. This is particularly useful for the recycling of the undesired products of kinetic resolutions of alcohols. By combination of such a racemisation with an acylation using isopropenyl or ethoxyvinyl esters as acyl donors, a fast straightforward recycling of starting materials may be achieved. The combined epimerisation and acylation process is demonstrated for the steroid estradiol methyl ether.
- Klomp, Dirk,Djanashvili, Kristina,Svennum, Nina Cianfanelli,Chantapariyavat, Nuttanun,Wong, Chung-Sing,Vilela, Filipe,Maschmeyer, Thomas,Peters, Joop A.,Hanefeld, Ulf
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p. 483 - 489
(2007/10/03)
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