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Search for "key intermediate" in Full Text gives 267 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

  • Daniel Wiegmann,
  • Stefan Koppermann,
  • Marius Wirth,
  • Giuliana Niro,
  • Kristin Leyerer and
  • Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

Graphical Abstract
  • . synthesised the hydroxyleucine moiety found in naturally occurring muraymycins of classes A to C (Scheme 8) [107]. Adapting a strategy developed by Zhu et al., D-serine (59) was stereoselectively converted into the protected amino alcohol 60 [108]. Key intermediate 60 was then Cbz- and acetonide protected to
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Published 22 Apr 2016

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

  • M. Fernanda N. N. Carvalho,
  • M. João Ferreira,
  • Ana S. O. Knittel,
  • Maria da Conceição Oliveira,
  • João Costa Pessoa,
  • Rudolf Herrmann and
  • Gabriele Wagner

Beilstein J. Org. Chem. 2016, 12, 732–744, doi:10.3762/bjoc.12.73

Graphical Abstract
  • Strecker degradation was proposed, which includes the anion formed by deprotonation of the carboxyl group as the key intermediate [28][29]. Indeed during geometry optimization we found that the decarboxylation of the anion formed from glycine and ninhydrin occurs without significant energy barrier. This
  • decarboxylation. Since the parent zwitterions 5 and 6 cannot be calculated as energy minima, there is no chance to understand, e.g., which conformations of 5 will lead preferentially to 7a and 7b, respectively. Since it was found experimentally that the amine 12 is the key intermediate for the formation of
  • hydrolysis of 11 was detected. This observation suggests that 10 is formed preferentially, and thus the key intermediate is rather 7b and not 8. Such proposal is supported by the calculated activation barrier for the formation of 10 from 7b which is slightly lower (2.2 kcal/mol) than the corresponding
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Published 18 Apr 2016

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

  • Giorgos Koutoulogenis,
  • Nikolaos Kaplaneris and
  • Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

Graphical Abstract
  • constructed via a desymmetrization aza-Michael reaction. That key intermediate 72 was afforded in 91% yield and 97% ee. (Scheme 25). In 2012, Cobb and co-workers developed a novel asymmetric Michael–Michael reaction between nitrohex-4-enoates 73 and nitroolefins 74 to construct a cyclohexene moiety, bearing
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Published 10 Mar 2016

Enabling technologies and green processes in cyclodextrin chemistry

  • Giancarlo Cravotto,
  • Marina Caporaso,
  • Laszlo Jicsinszky and
  • Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

Graphical Abstract
  • . Monosubstituted CD derivative preparation Mono 6I-(p-toluenesulfonyl)-β-CD is the most popular of the CD derivatives because it is a key intermediate in the synthesis of important amino, azido, thio, thiocyanate and halo-derivatives. 6I-(p-toluenesulfonyl)-β-CD was efficiently prepared in an US-assisted procedure
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Published 15 Feb 2016

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

  • Sophie Letort,
  • Sébastien Balieu,
  • William Erb,
  • Géraldine Gouhier and
  • François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

Graphical Abstract
  • disulfonylimidazole 42 to access a key intermediate easily converted to the corresponding di-2,3-mannoepoxido compound 43 (Scheme 8) [89]. The 3A,3B-diazido-3A,3B-dideoxy-bis(altro)-β-cyclodextrin 44 was then obtained by reaction of 43 with sodium azide and a copper(I)-catalyzed azide–alkyne cycloaddition finally
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Published 05 Feb 2016

Synthesis of cyclic N1-pentylinosine phosphate, a new structurally reduced cADPR analogue with calcium-mobilizing activity on PC12 cells

  • Ahmed Mahal,
  • Stefano D’Errico,
  • Nicola Borbone,
  • Brunella Pinto,
  • Agnese Secondo,
  • Valeria Costantino,
  • Valentina Tedeschi,
  • Giorgia Oliviero,
  • Vincenzo Piccialli and
  • Gennaro Piccialli

Beilstein J. Org. Chem. 2015, 11, 2689–2695, doi:10.3762/bjoc.11.289

Graphical Abstract
  • allowed the removal of both the OCE phosphate protecting groups together with the acetate function, thus obtaining the key intermediate 18 as triethylammonium salt after HPLC purification. The derivate 18, dissolved in DMF at the final concentration of 2 mM was treated with EDC (1.2 equiv) and the
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Published 22 Dec 2015

Catalytic asymmetric formal synthesis of beraprost

  • Yusuke Kobayashi,
  • Ryuta Kuramoto and
  • Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

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  • Yusuke Kobayashi Ryuta Kuramoto Yoshiji Takemoto Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan 10.3762/bjoc.11.285 Abstract The first catalytic asymmetric synthesis of the key intermediate for beraprost has been achieved through an
  • clinical application of 1, as well as the development of more active derivatives. Due to the unique tricyclic core of 1, which bears four contiguous stereocenters, various approaches for the synthesis of key intermediate 2 (Scheme 1) have been reported [14][15][16][17][18][19][20][21][22][23], including a
  • few asymmetric syntheses relying on the optical resolution of racemic intermediates [16][17][18][23]. Herein we report the first catalytic asymmetric synthesis of the key intermediate 2 through organocatalyzed-enantioselective intramolecular oxa-Michael reaction [24][25][26]. Results and Discussion
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Published 18 Dec 2015

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

  • Tatjana Huber,
  • Lara Weisheit and
  • Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

Graphical Abstract
  • tertiary amide was then formed by sequential reaction of carboxylic acid 53 with oxalyl chloride and N-methylaniline derivative 54. The following two-step debenzylation sequence afforded alcohol 55 which was converted to the corresponding mesylate, serving as a key intermediate for the construction of the
  • afforded coraxeniolide A (10) in 38% yield over three steps. Additionally, the enantioselective total synthesis of β-caryophyllene was realized starting from key intermediate 80. The route commenced with conjugate addition of silyl ketene acetal 81b to enone 80 from the sterically less hindered re-face
  • proceed via the chair-like transition state 104, afforded key intermediate 105 with high diastereo- and enantioselectivity. Preparation of the δ-lactone 106 of the A ring of xeniolide F was then realized by treatment of Claisen product 105 with the methylene Wittig reagent, followed by desilylation and
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Published 10 Dec 2015

Versatile synthesis and biological evaluation of novel 3’-fluorinated purine nucleosides

  • Hang Ren,
  • Haoyun An,
  • Paul J. Hatala,
  • William C. Stevens Jr,
  • Jingchao Tao and
  • Baicheng He

Beilstein J. Org. Chem. 2015, 11, 2509–2520, doi:10.3762/bjoc.11.272

Graphical Abstract
  • -ribofuranose (25) was then obtained in 33.13% overall yield after further treatment with acetic anhydride–acetic acid–sulfuric acid system. More than 200 g scale was achieved for the synthesis, and high purity (98%) product was obtained. This key intermediate 25 can be used to synthesize a variety of 3’-fluoro
  • provide the desired protected key intermediate 26 in 90% yield (Scheme 1). To construct the first series of fluorinated purine analogues, compound 26 was treated with a saturated solution of ammonia in methanol, which resulted in the amination at the 6-position and deprotection of the protecting groups to
  • -3’-fluoro-6-methylpurine riboside 4, the analogue of biologically active natural product, 6-methylpurine-β-D-riboside (6-β-D-MPR). We constructed 3’-deoxy-3’-fluororibofuranosylpurine nucleosides 5–11 with various aromatic and heterocyclic moieties at position 6 from the key intermediate 26 by
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Published 09 Dec 2015

Synthesis of D-fructose-derived spirocyclic 2-substituted-2-oxazoline ribosides

  • Madhuri Vangala and
  • Ganesh P. Shinde

Beilstein J. Org. Chem. 2015, 11, 2289–2296, doi:10.3762/bjoc.11.249

Graphical Abstract
  • to explore the scope of the synthesis and isolation of spirooxazolines. Thus, the required key intermediate D-psicofuranose 2a was synthesized in four steps from the readily available starting material D-fructose following the literature procedure [42][47]. The C6–OH group of D-psicofuranose was
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Published 24 Nov 2015

Molecular-oxygen-promoted Cu-catalyzed oxidative direct amidation of nonactivated carboxylic acids with azoles

  • Wen Ding,
  • Shaoyu Mai and
  • Qiuling Song

Beilstein J. Org. Chem. 2015, 11, 2158–2165, doi:10.3762/bjoc.11.233

Graphical Abstract
  • scope. The mechanistic studies reveal that oxygen plays an essential role in the success of the amidation reactions with copper peroxycarboxylate as the key intermediate. Transamidation occurs smoothly between azole amide and a variety of amines. Keywords: amidation; azoles; Cu-catalyzed; molecular
  • key intermediate to make the subsequent amide formation feasible (Scheme 1b). In our work, azoles have been chosen as the amines due to their special bioactivity [31]. To the best of our knowledge, Cu salt has not yet been used for catalyzed, oxidative direct amide formation. We report the first
  • amidation reaction from carboxylic acids with peroxycarboxylate as the key intermediate, which represents a novel activation mode with molecular oxygen as the activating reagent. Most remarkably, in sharp contrast to previous reports (which used complex N-containing ligands to form copper superoxide
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Published 11 Nov 2015

C–H bond halogenation catalyzed or mediated by copper: an overview

  • Wenyan Hao and
  • Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

Graphical Abstract
  • -halosuccinimide, X = Cl or Br). The application of different acids which participated in the in situ formation of acyl hypohalites enabled the selective generation of products 2 and 7 (Scheme 5). Notably, the C–H iodinated product of type 2 was also observed as key intermediate in the copper-catalyzed pyridinyl
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Published 09 Nov 2015

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

  • Marco G. Rigamonti and
  • Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

Graphical Abstract
  • the synthesis optimisation of the key intermediate 4 that can be prepared starting from (−)-isopulegol by two different approaches: i) oxidation of the hydroxy group to give (S)-isopulegone, which in turn is reduced stereospecifically into the desired cis diastereoisomer; or ii) by inversion of C(1
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Published 05 Nov 2015

Synthesis, antimicrobial and cytotoxicity evaluation of new cholesterol congeners

  • Mohamed Ramadan El Sayed Aly,
  • Hosam Ali Saad and
  • Shams Hashim Abdel-Hafez

Beilstein J. Org. Chem. 2015, 11, 1922–1932, doi:10.3762/bjoc.11.208

Graphical Abstract
  • each other. Conclusion In conclusion, cholesterol was successfully converted into 3β-azidocholest-5-ene (3) in good yield. This key intermediate, besides 3β-(prop-2-yn-1-yloxy)cholest-5-ene (10) were involved in a series of CuAAC reactions to afford a set of new modified cholesterols. The chalcone
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Published 16 Oct 2015

Recent applications of ring-rearrangement metathesis in organic synthesis

  • Sambasivarao Kotha,
  • Milind Meshram,
  • Priti Khedkar,
  • Shaibal Banerjee and
  • Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

Graphical Abstract
  • and co-workers [70] have described a total synthesis of norhalichondrin B in 37 steps from β-furylethanol. Interesting feature of this synthetic sequence is the tactical utilization of tandem ROM–RCM protocol towards the synthesis of the key intermediate 335. In this reaction, the required RRM
  • precursor 333 was obtained from diazo ester 331 in five steps. Further, the RRM of 333 with catalyst 2 furnished the required pyran derivative 334 (71%). Next, the fused ether 334 was transformed into the desired intermediate 335 in eight steps, which is a key intermediate required for the synthesis of
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Published 07 Oct 2015

The simple production of nonsymmetric quaterpyridines through Kröhnke pyridine synthesis

  • Isabelle Sasaki,
  • Jean-Claude Daran and
  • Gérard Commenges

Beilstein J. Org. Chem. 2015, 11, 1781–1785, doi:10.3762/bjoc.11.193

Graphical Abstract
  • (2) in the presence of ammonium acetate and gave 6-acetyl-2,2’:6’,2’’-terpyridine (4). This intermediate was cited by Potts [28] but to our knowledge, was not described. During the preparation of nonsymmetric quaterpyridines, 6-acetyl-2,2’:6’,2’’-terpyridine (4) is the key intermediate. Recently
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Published 30 Sep 2015

Dimethylamine as the key intermediate generated in situ from dimethylformamide (DMF) for the synthesis of thioamides

  • Weibing Liu,
  • Cui Chen and
  • Hailing Liu

Beilstein J. Org. Chem. 2015, 11, 1721–1726, doi:10.3762/bjoc.11.187

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  • ., Haidian District, Beijing 100875, P. R. China; Tel: +86-15010928428 10.3762/bjoc.11.187 Abstract An improved and efficient method for the synthesis of thioamides is presented. For this transformation, dimethylamine as the key intermediate is generated in situ from dimethylformamide (DMF). All the tested
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Published 23 Sep 2015

Towards inhibitors of glycosyltransferases: A novel approach to the synthesis of 3-acetamido-3-deoxy-D-psicofuranose derivatives

  • Maroš Bella,
  • Miroslav Koóš and
  • Chun-Hung Lin

Beilstein J. Org. Chem. 2015, 11, 1547–1552, doi:10.3762/bjoc.11.170

Graphical Abstract
  • protected open-chain form of 3-acetamido-3-deoxy-D-psicose, namely 3-acetamido-3-deoxy-4,5-O-isopropylidene-6-O-pivaloyl-1-O-trityl-D-psicose (7) in an excellent yield (Scheme 1). This compound represents the key intermediate for the further synthesis of 3-acetamido-3-deoxy-D-psicofuranose derivatives
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Published 04 Sep 2015

Selected synthetic strategies to cyclophanes

  • Sambasivarao Kotha,
  • Mukesh E. Shirbhate and
  • Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

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Published 29 Jul 2015

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

  • Marcus Baumann and
  • Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

Graphical Abstract
  • worked well. As seen above, avoiding detrimental exotherms in scale up campaigns is a common reason for developing a continuous flow process. This approach is also demonstrated in the synthesis of the pyrrolotriazinone 73 via a exothermic oxidative rearrangement from 75, a key intermediate towards
  • key intermediate 83 at pilot-scale, a flow-based asymmetric hydrogenation was chosen as an economically more viable option compared to establishing a high-pressure batch process. As depicted in Scheme 14, solutions of the substrate 84 and a zinc triflate additive were combined with the rhodium
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Published 17 Jul 2015

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

  • Luke J. O’Driscoll,
  • Sissel S. Andersen,
  • Marta V. Solano,
  • Dan Bendixen,
  • Morten Jensen,
  • Troels Duedal,
  • Jess Lycoops,
  • Cornelia van der Pol,
  • Rebecca E. Sørensen,
  • Karina R. Larsen,
  • Kenneth Myntman,
  • Christian Henriksen,
  • Stinne W. Hansen and
  • Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

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  • ) are versatile functional groups in many areas of chemistry. The large-scale synthesis of the key intermediate 6 improves the accessibility of these species and their derivatives. The related species 7 can be used to prepare further analogues. Compounds 6 and 7 can both be used to prepare BPTTFs and
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Published 03 Jul 2015

A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

  • Gleb Sorohhov,
  • Chenyi Yi,
  • Michael Grätzel,
  • Silvio Decurtins and
  • Shi-Xia Liu

Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118

Graphical Abstract
  • , the synthesis of the key intermediate 7 involves the protection of one aldehyde group as an acetal using pinacol prior to HWE reaction of 5 with 4,5-bis(hexylthio)-1,3-dithiole-2-thione, followed by deprotection under acidic conditions. Aldehyde 5 was readily obtained by palladium-catalyzed Suzuki
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Published 22 Jun 2015

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

  • Martin Weiser,
  • Sergej Hermann,
  • Alexander Penner and
  • Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

Graphical Abstract
  • additive. Photocatalytic additions of a variety of alcohols gave the corresponding products in good to excellent yields. The proposed photocatalytic electron transfer mechanism was supported by detection of the PDI radical anion as key intermediate and by comparison of two intramolecular reactions with
  • protonated rapidly to the neutral radical that is the key intermediate to explain the Markovnikov selectivity of this route. Both steps, electron transfer and protonation, could also occur in one proton-coupled electron transfer step. Back electron transfer to the photocatalyst finishes the photocatalytic
  • the corresponding products in good to excellent yields. Similar to the reductive mode, the oxidative nucleophilic addition needed the additive Ph–SH as electron and proton shuttle. The proposed photocatalytic electron transfer mechanism was supported by the observation of the PDI radical anion as key
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Published 27 Apr 2015

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

  • Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

Graphical Abstract
  • and co-workers performed the rhodium-catalyzed ECA of 51 to yield 4-arylpiperidinone 52. Compound 52 is a key intermediate in the synthesis of the pharmaceutical agent, (−)-paroxetine [142] (Scheme 13). In 2001, Sakuma and Miyaura reported the first rhodium-catalyzed asymmetric 1,4-addition of α,β
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Published 23 Apr 2015

Copper-catalyzed cascade reactions of α,β-unsaturated esters with keto esters

  • Zhengning Li,
  • Chongnian Wang and
  • Zengchang Li

Beilstein J. Org. Chem. 2015, 11, 213–218, doi:10.3762/bjoc.11.23

Graphical Abstract
  • conjugate reduction of the α,β-unsaturated diester with newly generated copper hydride, followed by aldol reaction to yield the key intermediate alkoxide A, which is subjected to further lactonization to form the lactone. Lam’s group has furnished a cobalt-catalyzed conjugate reductive aldolization
  • of γ-carboxy-γ-lactones via a copper-catalyzed cascade reaction. Considering that the reported conjugate addition–aldolization–lactonization cascade reactions proceed via the key intermediate A in Figure 1, we envisioned that the conjugate reduction of a methacrylate and the following aldol reaction
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Published 06 Feb 2015
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