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Search for "stereoselective" in Full Text gives 563 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Multiple threading of a triple-calix[6]arene host

  • Veronica Iuliano,
  • Roberta Ciao,
  • Emanuele Vignola,
  • Carmen Talotta,
  • Patrizia Iannece,
  • Margherita De Rosa,
  • Annunziata Soriente,
  • Carmine Gaeta and
  • Placido Neri

Beilstein J. Org. Chem. 2019, 15, 2092–2104, doi:10.3762/bjoc.15.207

Graphical Abstract
  • stereoselective formation of endo-alkyl pseudo[n]rotaxane stereoisomers. Keywords: calixarene; multiple-threading; pseudo[n]rotaxane; stereoisomers; Introduction The self-assembly [1] of smaller components to larger aggregates represents one of the most spectacular phenomena in supramolecular chemistry [2][3][4
  • , DOSY, and ESI-FT-ICR MS/MS experiments. In addition, in the presence of a directional butylbenzylammonium axle, the stereoselective formation of endo-alkyl pseudorotaxane stereoisomers was observed. Experimental HR mass spectra were acquired on a FT-ICR mass spectrometer equipped with a 7T magnet. The
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Published 03 Sep 2019

α-Photooxygenation of chiral aldehydes with singlet oxygen

  • Dominika J. Walaszek,
  • Magdalena Jawiczuk,
  • Jakub Durka,
  • Olga Drapała and
  • Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

Graphical Abstract
  • methodologies enabling their functionalization, particularly in a stereoselective manner. Among them, asymmetric α-oxygenation of aldehydes still represents a challenging task. Most efficient methods require simultaneous use of chiral amines or Brønsted acids, and harsh oxidants like nitrosobenzene [1][2][3
  • ) or a chiral auxiliary (i.e., oxazolidinone) into the substrate structure is required for highly stereoselective reactions [20][21][22]. ‘One-pot’ photochemical α,β-functionalization of cinnamaldehyde Over the last few years, photochemical methods for asymmetric functionalisation of carbonyl compounds
  • diastereo- and enantioselective manner providing the presence of a substituent at the β-position. Using our procedure enantiopure (S)-3,4-diphenylbutanal ((S)-1) was transformed into (2R,3R)-3,4-diphenylbutane-1,2-diol in a highly stereoselective manner. This high level of stereoselectivity is rarely
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Published 30 Aug 2019

A review of the total syntheses of triptolide

  • Xiang Zhang,
  • Zaozao Xiao and
  • Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

Graphical Abstract
  • isomerization of olefin 43, the benzylic oxidation of 8, the use of m-CPBA to introduce the C-9,11 epoxide and the non-stereoselective reduction of the C-14 carbonyl group using sodium borohydride, caused an unacceptable overall yield (1.6%). This pioneering work undoubtedly established the basis for the future
  • form the A- and D-ring. The second one involves the reaction of the bicyclic intermediate 13 and 2-isopropyl-1,4-benzoquinone (14) to form the B- and C-ring. Finally, a regio- and stereoselective reduction, methylation and dehydration procedure and a selenylation, oxidation and elimination procedure
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Published 22 Aug 2019

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

  • Jason Yin Hei Man and
  • Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

Graphical Abstract
  • stabilize a particular stereoisomer over the others, thus making the 6R synthesis stereoselective. Moreover, as the secondary face in γ-CD (diameter ≈ 8.3 Å [49]) is much wider than the rim of CB[6] (diameter ≈ 5.8 Å [50]), it is expected that the primary face of γ-CD (diameter ≈ 7.5 Å [49]) will have a
  • macrocycles in 6R that results in a cooperative interaction so that the formation of 6R is stereoselective. With one less γ-CD in 5R, interactions between the axle and the macrocycles alone are only enough for interlocking the macrocycle, but not sufficient to drive a specific orientation of all the γ-CD
  • synthesis of 6R is stereoselective and only one stereoisomer was formed, probably due to the cooperative interactions between the CB[6] and the γ-CD on the fully occupied axle of 6R. These findings will provide better insight on the use of intercomponent interactions to control the stereochemistry of
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Published 01 Aug 2019

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

  • Rosana Ribić,
  • Ranko Stojković,
  • Lidija Milković,
  • Mariastefania Antica,
  • Marko Cigler and
  • Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

Graphical Abstract
  • performed. Boc deprotection of obtained compound 6 gave the trifluoroacetic salt of peptide 7 which was used in the synthesis of mannoconjugates. The mannose precursor containing the glycolyl linker 11 was prepared in a three-step procedure shown in Scheme 3. The stereoselective α-anomeric deacetylation of
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Published 29 Jul 2019

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

  • Iwona E. Głowacka,
  • Aleksandra Trocha,
  • Andrzej E. Wróblewski and
  • Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

Graphical Abstract
  • structurally related since they contain an (R)-1-aryl-2-propanamine moiety. The synthesis of the respective intermediates (R)-16 and (R)-17 commenced from the ester (2R,1'R)-5f and relied on arylation of Weinreb amide (2R,1'R)-18 to afford the aziridine ketone 19. Its highly stereoselective reduction with the
  • stereochemistry, they were synthesized from the aziridine ketone (2S,1'R)-36 readily available from Weinreb amide (2S,1'R)-18 which already contained the required configuration at C2 (Scheme 11) [47]. Introduction of the 3R configuration in xestoaminol C and 3S in its epimer was achieved by stereoselective
  • activity [56]. Alkylation of Weinreb amide (2S,1'S)-18 and stereoselective reduction of the corresponding ketone (2S,1'S)-56 with the NaBH4/ZnCl2 mixture gave the aziridine alcohol (2S,1'R,1''S)-57 already containing exact absolute configurations (2S and 3R) of the final product (Scheme 16) [57]. A two
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Published 23 Jul 2019

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

  • Gagandeep Kour Reen,
  • Ashok Kumar and
  • Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Graphical Abstract
  • high level of functional group compatibility, intramolecular alkylations, inter and intramolecular C–H bond activation and regio/stereoselective homocoupling of alkynes [71][72][73]. Group of Cho and Chang have unprecedentedly reported a Rh catalytic system for facile addition of heteroarenes to both
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Published 19 Jul 2019

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

  • András György Németh,
  • György Miklós Keserű and
  • Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

Graphical Abstract
  • discovered, including HIV-1 reverse transcriptase inhibition activity [6][7][8][9][10][11]. Moreover, their utilization as highly regio- and stereoselective organocatalysts in specific types of chemical tranformations [12][13][14][15][16][17] was introduced, as well. More recently, O-thiocarbamates have been
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Published 10 Jul 2019

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

  • Anthony Choi,
  • Rebecca M. Morley and
  • Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

Graphical Abstract
  • could be converted to other derivatives by Suzuki–Miyaura coupling, reduction or oxidation reactions. Keywords: azomethine ylide; cycloaddition; heterocycle; pyrrolidine; stereoselective; Introduction Cycloaddition reactions of azomethine ylides are an important class of pericyclic reactions that give
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Published 03 Jul 2019

Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy

  • Daniela Imperio,
  • Erika Del Grosso,
  • Silvia Fallarini,
  • Grazia Lombardi and
  • Luigi Panza

Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135

Graphical Abstract
  • , where, among other derivatives, 1,2-dideoxy-ᴅ-glucopyranos-2-ylboronic acid has been synthesized through a regio- and stereoselective hydroboration of persilylated glucal. Considering the different substitution positions for the boronic acid in the sugar skeleton, we were curious to observe the chemical
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Published 19 Jun 2019

Robust perfluorophenylboronic acid-catalyzed stereoselective synthesis of 2,3-unsaturated O-, C-, N- and S-linked glycosides

  • Madhu Babu Tatina,
  • Xia Mengxin,
  • Rao Peilin and
  • Zaher M. A. Judeh

Beilstein J. Org. Chem. 2019, 15, 1275–1280, doi:10.3762/bjoc.15.125

Graphical Abstract
  • ]. The Ferrier rearrangement is one of the most useful processes to synthesize pseudo-glycosides in a direct and stereoselective fashion. Several classes of catalysts have been successfully applied in the Ferrier rearrangement including Brønsted acids [7][8][9][10][11][12][13], Lewis acids [14][15][16
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Published 11 Jun 2019

Steroid diversification by multicomponent reactions

  • Leslie Reguera,
  • Cecilia I. Attorresi,
  • Javier A. Ramírez and
  • Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

Graphical Abstract
  • MCR is due to the ring contraction of the 7-membered ring cyclic intermediate by transannular acyl transfer, which leads to the β-lactam derivative. Despite the chiral nature of the steroidal substrate, no significant stereoselective induction was observed, probably because the 7-membered ring
  • steroidal isocyanide 31 to the imine (or aminal) leads to the stereoselective formation of the α-adduct intermediates, which rearranges to the final tetrahydropyridine ring 32. Besides the use of steroids as oxo, amine, carboxylic acid and isocyanide components, there is a very early report by Dumestre et
  • ]. Synthesis of ecdysteroid derivatives by Ugi-4CR using a steroidal isocyanide [30]. Stereoselective multicomponent synthesis of a steroid–tetrahydropyridine hybrid using a chiral bifunctional substrate and a cholestanic isocyanide. DBA: 3,5-dinitrobenzoic acid [31]. Pd(II)-catalyzed three-component reaction
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Published 06 Jun 2019

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

  • Herman O. Sintim,
  • Hamad H. Al Mamari,
  • Hasanain A. A. Almohseni,
  • Younes Fegheh-Hassanpour and
  • David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

Graphical Abstract
  • –Stevens-derived diazoesters 23 and 27, respectively. Only triethylsilyl-protected diazoester 27 proved viable to deliver a diazoketone 28. The latter underwent stereoselective carbonyl ylide formation–cycloaddition with methyl glyoxylate and acid-catalysed rearrangement of the resulting cycloadduct 29, to
  • area have recently culminated in two communicated syntheses of 6,7-dideoxysqualestatin H5 (DDSQ (2), Figure 1) [12][13]. The centrepiece of both of these strategies is a rhodium(II)-catalysed tandem carbon ylide formation from a diazoketone 3 (Scheme 1) and stereoselective [3 + 2] cycloaddition with a
  • asymmetric variant of our aldol route (α-diazoacetate ester anion addition to an α-ketoester) to the cycloaddition substrate 3 (X = H) did not appear promising [16]. An alternative and asymmetric route to such substrates, ultimately successful, built on stereoselective alkylation of enolates of tartrates
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Published 31 May 2019

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

  • Edorta Martínez de Marigorta,
  • Jesús M. de Los Santos,
  • Ana M. Ochoa de Retana,
  • Javier Vicario and
  • Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

Graphical Abstract
  • derivatives do it through the carbon at 3-position. Although a quaternary stereocentre is created in the process, no attempts to make this synthesis in a stereoselective fashion were reported. A tentative mechanism is proposed, based in a Sonogashira coupling of iodobenzamide 17 and copper acetylide, in a
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Published 08 May 2019

Mechanistic investigations on multiproduct β-himachalene synthase from Cryptosporangium arvum

  • Jan Rinkel and
  • Jeroen S. Dickschat

Beilstein J. Org. Chem. 2019, 15, 1008–1019, doi:10.3762/bjoc.15.99

Graphical Abstract
  • formation of compounds 3, 5 and 6, the stereochemical course of these final steps could be followed by stereoselective deuterations. GC–MS analysis of the products obtained from the incubations with HcS, FPPS, DMAPP and (Z)- or (E)-(4-13C,4-2H)IPP showed a specific loss of HZ in all cases (Figure 4
  • )-(1-2H)IPP and (2-13C)DMAPP with FPPS and HcS also allowed for the assignment of the newly introduced diastereotopic position at C-10 (Figure 9). Together with the assignment of the hydrogens by NOESY in 1, these data show a stereoselective incorporation of HR-1 into the Hα-position at C-10 by a
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Published 02 May 2019

An efficient synthesis of the guaiane sesquiterpene (−)-isoguaiene by domino metathesis

  • Yuzhou Wang,
  • Ahmed F. Darweesh,
  • Patrick Zimdars and
  • Peter Metz

Beilstein J. Org. Chem. 2019, 15, 858–862, doi:10.3762/bjoc.15.83

Graphical Abstract
  • stereoselective Michael addition of aldehyde 4 to methyl vinyl ketone [7][8][10] followed by chemoselective elaboration of the two carbonyl functions. Finally, aldehyde 4 was traced back to the commercially available starting material (S)-citronellal (5). On the other hand, a more rarely used enediyne metathesis
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Published 09 Apr 2019

Diastereo- and enantioselective preparation of cyclopropanol derivatives

  • Marwan Simaan and
  • Ilan Marek

Beilstein J. Org. Chem. 2019, 15, 752–760, doi:10.3762/bjoc.15.71

Graphical Abstract
  • ]. Several reliable approaches to produce cyclopropanols have been reported in the literature (Scheme 1) [6] but a number of challenges still exist particularly for the stereoselective preparation of cyclopropanols of high structural complexity and substitution pattern. Since the first synthesis of
  • different strategy is required for every cyclopropanol and cyclopropylamine that one needs to prepare, limiting the rapid structural diversification which is usually essential for biological studies. From this rapid tour d’horizon, it is clear that if one could design a stereoselective synthetic pathway to
  • and useful entry to the synthesis of these heterosubstituted three-membered rings. Results and Discussion To reach these goals, we are describing herein the diastereo- and enantioselective carbometalation reaction of cyclopropenes to provide cyclopropylmetal species. By subsequent stereoselective
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Published 21 Mar 2019

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

  • Gábor Benkovics,
  • Mihály Bálint,
  • Éva Fenyvesi,
  • Erzsébet Varga,
  • Szabolcs Béni,
  • Konstantina Yannakopoulou and
  • Milo Malanga

Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66

Graphical Abstract
  • based on stereoselective interactions of CDs with guest molecules (chiral separations, asymmetric catalysis, enzyme mimics) [20]. However, if the target is only the side-selectivity of difunctionalization, pseudoenantiomeric mixtures of the regioisomers can be used [21]. For CD-based multifunctional
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Published 18 Mar 2019

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

  • Jan Hendrik Lang and
  • Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

Graphical Abstract
  • assembled by solution-phase synthesis and an open-chain analogue of the natural product was obtained. Keywords: jasplakinolide; marine natural products; Negishi coupling; polyketides; stereoselective synthesis; Introduction Our program on the synthesis of biologically active natural products with peptide
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Published 28 Feb 2019

Selectivity in multiple multicomponent reactions: types and synthetic applications

  • Ouldouz Ghashghaei,
  • Francesca Seghetti and
  • Rodolfo Lavilla

Beilstein J. Org. Chem. 2019, 15, 521–534, doi:10.3762/bjoc.15.46

Graphical Abstract
  • (Scheme 11B). This compound does not react under the initial reaction conditions, but can be forced to do so in a Joullié MCR with a new isocyanide/carboxylic acid pair [47]. Incidentally, this last process is also remarkably stereoselective, something very unusual in Ugi-type reactions. Finally, to
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Published 21 Feb 2019

Convergent synthesis of the pentasaccharide repeating unit of the biofilms produced by Klebsiella pneumoniae

  • Arin Gucchait,
  • Angana Ghosh and
  • Anup Kumar Misra

Beilstein J. Org. Chem. 2019, 15, 431–436, doi:10.3762/bjoc.15.37

Graphical Abstract
  • unit of biofilms produced by Klebsiella pneumoniae, has been synthesized using a stereoselective [2 + 3] convergent glycosylation strategy. The β-D-mannosidic moiety has been synthesized using a D-mannose-derived thioglycoside by a two-step activation process. Late stage TEMPO-mediated oxidation of the
  • using a set of stereoselective glycosylations of a number of suitably functionalized monosaccharide derivatives 2, 3 [14], 4, 5 [15], 6 [16] and 7 [17], which were prepared from the commercially available reducing monosaccharides using a number of functional group manipulations reported earlier (Figure
  • -benzylidene-β-D-glucopyranoside (11) in 70% yield. Stereoselective glycosylation of compound 11 with D-mannose-derived ethyl 2-O-acetyl-3,4,6-tri-O-benzyl-1-thio-α-D-mannopyranoside (3) [14] in the presence of a combination of N-iodosuccinimide (NIS) and trimethylsilyl trifluoromethanesulfonate (TMSOTf) [22
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Published 13 Feb 2019

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

  • Mikhail V. Makarov and
  • Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

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  • -ribofuranose (2a) for the synthesis of β-NR+Br−. 2.1.2. Glycosylation with 1,2,3,5-tetra-O-acyl-ribofuranoses by the silyl-Hilbert–Johnson method: Further developments in a more efficient and stereoselective synthesis of NR+ salt forms were achieved by the application of the silyl-Hilbert–Johnson method based
  • dry dichloromethane resulting in the stereoselective formation of the corresponding β-isomer 17 of O-ethyl nicotinate riboside in high yield. It was speculated that less polar solvents, such as DCM, contribute to the formation of a less dissociated transition state, similar to F in Figure 3 above
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Published 13 Feb 2019

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

  • Guillaume Ernouf,
  • Jean-Louis Brayer,
  • Christophe Meyer and
  • Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

Graphical Abstract
  • stereoselective access to a wide variety of heterosubstituted and/or functionalized alkylidenecyclopropanes which would not be readily accessible by other strategies. The different [2,3]- and [3,3]-sigmatropic rearrangements of cyclopropenylcarbinol derivatives disclosed to date, as well as the analysis of their
  • of cyclopropenylcarbinyl acetates provides a straightforward and stereoselective entry to alkylidene(acyloxycyclopropanes). Only a few compounds of this family had been previously generated by photochemical reactions (from 4-isopropylidene-3,3-dimethyl-1-thietan-2-thione [38] or from a 4-alkylidene
  • compounds 78 (98%) and 79 (99%), and to the azabicyclic product 80 (45%), respectively, with high diastereoselectivities (Scheme 27) [61][65]. Conclusion In recent years, [2,3]- and [3,3]-sigmatropic rearrangements of cyclopropenylcarbinol derivatives have emerged as useful tools for the stereoselective
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Published 05 Feb 2019

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

  • Patrycja Żak and
  • Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

Graphical Abstract
  • by cross metathesis with a series of 4-substituted styrenes and allylbenzene, in the presence of Ru-1 (Scheme 13) [19]. Under optimized conditions reactions led to fully chemo- and stereoselective formation of disubstituted germasilsesquioxanes. The ability of alkyldisiloxyvinylgermane to be
  • the application of ADMET in the synthesis of oligomers or polymers containing a POSS unit in the main chain. Marciniec disclosed ADMET copolymerization of DDSQ-2SiVi with dienes in the stereoselective synthesis of a new class of vinylene–arylene copolymers containing double-decker silsesquioxanes in
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Published 04 Feb 2019

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

  • Jesús González,
  • Alba de la Fuente,
  • María J. González,
  • Laura Díez de Tejada,
  • Luis A. López and
  • Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

Graphical Abstract
  • stereoselective reaction. Once more, simple ZnCl2 was particularly effective for this reaction in sharp contrast to the incompetence of [Rh2(OAc)4]. It should be noticed that 1,2-divinylcyclopropanes 3a–l did not undergo [3,3]-Cope rearrangements under the reaction conditions. Moreover, when pure endo-3e was
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Published 30 Jan 2019
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