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Search for "stereochemistry" in Full Text gives 570 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Absolute configurations of talaromycones A and B, α-diversonolic ester, and aspergillusone B from endophytic Talaromyces sp. ECN211

  • Ken-ichi Nakashima,
  • Junko Tomida,
  • Takao Hirai,
  • Yoshiaki Kawamura and
  • Makoto Inoue

Beilstein J. Org. Chem. 2020, 16, 290–296, doi:10.3762/bjoc.16.28

Graphical Abstract
  •  4b). This is the first experimental evidence that corroborates the absolute configurations of 3 and 4, compounds that were reported previously without evidence for this stereochemistry. We also obtained single crystals of glauconic acid (5) as prisms by slow evaporation in CH2Cl2/n-hexane at 10 °C. X
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Published 28 Feb 2020

Combination of multicomponent KA2 and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

  • Riccardo Innocenti,
  • Elena Lenci,
  • Gloria Menchi and
  • Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

Graphical Abstract
  • reduced gauche interactions [55]. Subsequent epoxidation at the double bond directed by the hydroxy group and using m-chloroperbenzoic acid allowed to install two additional stereocenters with complete control of the relative stereochemistry in 68% yield. Such two-step synthesis proved to proceed also in
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Published 12 Feb 2020

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

  • Katarzyna Włodarczyk,
  • Piotr Borowski and
  • Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

Graphical Abstract
  • reaction. In the presence of a Brønsted acid, mainly [1,3]-rearrangement is observed, whereas a Lewis acid catalyzes the [1,4]-sulfur migration. To gain insight into the mechanism of these transformations, the stereochemistry of these rearrangements have been tested, along with the conduction of some
  • control experiments and DFT calculations. Keywords: Brønsted and Lewis acids; DFT; mechanistic studies; rearrangement; stereochemistry; sulfur atom migration; Introduction Among all organic reactions, rearrangements are an exciting class of transformations where unusual or even unexpected products can
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Published 21 Jan 2020

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

  • Damian Kusy,
  • Agata Wojciechowska,
  • Joanna Małolepsza and
  • Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

Graphical Abstract
  • of the desired products were formed. The structures of products 3 and 6–22 were confirmed by spectroscopic methods, 1H, 13C, 31P NMR, and MS analysis. The stereochemistry of the newly formed double bond was evaluated by 1H NMR spectroscopy. Next, we determined the influence of the position of a
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Published 03 Jan 2020

Regioselectivity of glycosylation reactions of galactose acceptors: an experimental and theoretical study

  • Enrique A. Del Vigo,
  • Carlos A. Stortz and
  • Carla Marino

Beilstein J. Org. Chem. 2019, 15, 2982–2989, doi:10.3762/bjoc.15.294

Graphical Abstract
  • HMBC analysis, which was particularly useful in the cases in which only one product was detected. For example, for compound 14α, correlations between signals corresponding to H-1' and C-3 and between C-1' and H-3 were observed. The stereochemistry of the newly formed glycosidic linkages was established
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Published 19 Dec 2019

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

  • Eric J. N. Helfrich,
  • Geng-Min Lin,
  • Christopher A. Voigt and
  • Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

Graphical Abstract
  • . Using enantiotopically doubly 13C-2H-labeled substrates, it is possible to determine the stereochemistry of a cyclization product by locating the 2H atom and its relative position to other stereocenters [75]. In vitro terpene biosynthesis, however, might not always result in the production of the
  • , simply by rationally mutating the active-site residues. The majority of bacterial type II diterpene TCs produce bicyclic labdane, halimadane, or clerodane skeletons with different stereochemistry, levels of unsaturation, and hydroxylation patterns [124], which undergo further conversion with their
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Published 29 Nov 2019

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

  • Vito A. Fiore,
  • Chiara Freisler and
  • Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

Graphical Abstract
  • XRD analysis (vide supra), the stereochemistry at the P-substituted olefinic bond could be determined in all cases from characteristic chemical shifts of the olefinic proton and from 3J(P,H) and 3J(P,C) coupling constants. The olefinic proton signal of the E-isomers was found in the δ range 6.8–7.7
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Published 01 Nov 2019

Chemical synthesis of the pentasaccharide repeating unit of the O-specific polysaccharide from Escherichia coli O132 in the form of its 2-aminoethyl glycoside

  • Debasish Pal and
  • Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2019, 15, 2563–2568, doi:10.3762/bjoc.15.249

Graphical Abstract
  • from E. coli O132 is accomplished in the form of its 2-aminoethyl glycoside. The 2-aminoethyl glycoside is particularly important as it allows further glycoconjugate formation utilizing the terminal amine without affecting the stereochemistry of the reducing end. The target was achieved through a [3
  • manipulations on the commercially available monosaccharides and stereoselective chemical glycosylations. The 2-aminoethyl glycoside at the reducing end will facilitate further glycoconjugate formation without hampering the stereochemistry of the anomeric center. We have used similar glycosides in case of other
  • Discussion It is important to select a suitable glycoside at the reducing end of the target oligosaccharide keeping in mind that the glycoside should allow further glycoconjugate formation without disturbing the stereochemistry of the anomeric center. Therefore, the 2-aminoethyl glycoside was selected at the
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Published 28 Oct 2019

Synthesis of novel sulfide-based cyclic peptidomimetic analogues to solonamides

  • José Brango-Vanegas,
  • Luan A. Martinho,
  • Lucinda J. Bessa,
  • Andreanne G. Vasconcelos,
  • Alexandra Plácido,
  • Alex L. Pereira,
  • José R. S. A. Leite and
  • Angelo H. L. Machado

Beilstein J. Org. Chem. 2019, 15, 2544–2551, doi:10.3762/bjoc.15.247

Graphical Abstract
  • sequence displayed by 9e and 9h, the stereochemistry of the Phe residue is detrimental to the antihemolytic activity; (3) in a similar sense, for 9f and 9g, diastereosiomers on the Ile residue, the L-configuration on this residue is necessary to the observed hemolysis inhibition by S. aureus. Conclusion A
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Published 25 Oct 2019

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

  • Anna Kmieciak and
  • Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

Graphical Abstract
  • hydrolyzed with a 5% aqueous solution of NaOH. GC analysis of the isolated alcohol confirmed the presence of (1R,4S,5R)-apopinenol (18) and (1R,4R,5R)-16 in a ratio of 79.5:20.5. The structures and stereochemistry of both diastereomeric alcohols 16 and 18 were confirmed by 2D NMR spectra. All protons in 16
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Published 22 Oct 2019

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

  • Zhen Cao,
  • Aline Lacoudre,
  • Cybille Rossy and
  • Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

Graphical Abstract
  • diastereoisomers by coordination which had different geometries. Thereafter, the silver(I) complexes are discussed with the proposed stoichiometry from X-ray and NMR data, without accounting for stereochemistry: M2L2 for AgOTf and AgOTFA complexes (1a,b), M6L4 for AgNO3 one (1c) and M2L complex with PPh3AgOTf (1d
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Published 17 Oct 2019

Indium-mediated C-allylation of melibiose

  • Christian Denner,
  • Manuel Gintner,
  • Hanspeter Kählig and
  • Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

Graphical Abstract
  • of this post-transition metal for the elongation of carbohydrates [3][4][5]. Additional contributions were reported in the literature by Paquette and co-workers concerning indium-mediated reactions in water and their stereochemistry [6][7]. Based on these findings this elongation method has been
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Published 16 Oct 2019

In water multicomponent synthesis of low-molecular-mass 4,7-dihydrotetrazolo[1,5-a]pyrimidines

  • Irina G. Tkachenko,
  • Sergey A. Komykhov,
  • Vladimir I. Musatov,
  • Svitlana V. Shishkina,
  • Viktoriya V. Dyakonenko,
  • Vladimir N. Shvets,
  • Mikhail V. Diachkov,
  • Valentyn A. Chebanov and
  • Sergey M. Desenko

Beilstein J. Org. Chem. 2019, 15, 2390–2397, doi:10.3762/bjoc.15.231

Graphical Abstract
  • the final confirmation of the structure and to establish the relative stereochemistry of both stereoisomers. NOESY cross-peaks between signals of NH and OH protons revealed that A and B are in fact stereoisomers, rejecting the regioisomeric structure 14’. The different 3J values between 6-H and 7-H
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Published 08 Oct 2019

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

  • Ronja Driller,
  • Daniel Garbe,
  • Norbert Mehlmer,
  • Monika Fuchs,
  • Keren Raz,
  • Dan Thomas Major,
  • Thomas Brück and
  • Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

Graphical Abstract
  • generate a vast number of (poly)cyclic hydrocarbon scaffolds. Remarkably, this complex chemical reaction, comprising changes in bonding, hybridization as well as the introduction of specific stereochemistry, is performed in a single reaction cascade without consumption of a cofactor [11]. In this review we
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Published 02 Oct 2019

Perspective isomorphs – a new classification of molecular structures based on artistic and chemical concepts

  • Jannis Neumann,
  • Ansgar Schnurr and
  • Hermann A. Wegner

Beilstein J. Org. Chem. 2019, 15, 2319–2326, doi:10.3762/bjoc.15.224

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  • substances by transforming their structural information into an explicit character sequence for identification. The information is given in terms of layers around the atoms and their bond connectivity, tautomeric information, isotope information, stereochemistry, and electronic charge information. In
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Published 30 Sep 2019

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

  • Xiaowei Li,
  • Xiaolin Shi,
  • Xiangqian Li and
  • Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Graphical Abstract
  • substrates was reported by Yu and co-workers (Scheme 13) [50]. Enantioenriched benzyl fluorides were obtained by aid of a chiral α-amino amide transient directing group (TDG). Notably, the condensation of this bulky amino amide with the aldehyde led to control of the stereochemistry of the C–H insertion step
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Published 23 Sep 2019

An overview of the cycloaddition chemistry of fulvenes and emerging applications

  • Ellen Swan,
  • Kirsten Platts and
  • Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

Graphical Abstract
  • ][172][174][176][183][186][227][229]. There are very few papers reporting the aforementioned reaction occurring in aqueous conditions [175] most likely as a result of the poor solubility of fulvene derivatives in water [175]. Although the stereochemistry of DACs can usually be predicted by the ‘endo
  • ] or diphenylfulvene [20][103][114][133][163][180]. In each instance, the endo stereochemistry of the cycloadduct is dominant [91][176][180], indicating that the fulvene substituents in the exocyclic C6 position are too distal to impact the stereoselectivity [76][229]. There are documented cases of
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Published 06 Sep 2019

Isolation and characterisation of irinans, androstane-type withanolides from Physalis peruviana L.

  • Annika Stein,
  • Dave Compera,
  • Bianka Karge,
  • Mark Brönstrup and
  • Jakob Franke

Beilstein J. Org. Chem. 2019, 15, 2003–2012, doi:10.3762/bjoc.15.196

Graphical Abstract
  • reported so far [14]. To elucidate the relative stereochemistry of irinans A (2) and B (3), we analysed NOESY data (Figure 2). In the case of irinan A (2), the β configuration of OH-4 was deduced by the NOESY correlation OH-4/CH3-19. OH-14 was assigned as α based on the correlations OH-14/H-12α and H-9/H
  • -12α. The 5,6-epoxide was determined as β by a correlation from H-6 to H-3. These assignments are in complete agreement with the relative stereochemistry of 4ß-hydroxywithanolide E (1). In irinan B, the configuration of OH-14 could not be unambiguously inferred from NOE data due to the signal overlap
  • of H-15 with H-12 and other protons. As an alternative, OH-14 α configuration was deduced from the chemical shifts of C-12 and C-9, which experience a strong shielding γ-gauche effect for OH-14α configurations [21]. These data indicate a relative stereochemistry of irinan B matching withanolide F (5
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Published 23 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
  • the desired stereochemistry of the C-7 benzylic hydroxy group. Compound 46 was converted to triptonide 2 by Alder periodate reaction (NaIO4, 74%), and a sequencing m-CPBA epoxidation and basic hydrogen peroxide oxidation (H2O2/OH−) procedure (two steps, 28%). Finally, sodium borohydride reduction of 2
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Published 22 Aug 2019

Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica

  • Silvie Rimpelová,
  • Michal Jurášek,
  • Lucie Peterková,
  • Jiří Bejček,
  • Vojtěch Spiwok,
  • Miloš Majdl,
  • Michal Jirásko,
  • Miloš Buděšínský,
  • Juraj Harmatha,
  • Eva Kmoníčková,
  • Pavel Drašar and
  • Tomáš Ruml

Beilstein J. Org. Chem. 2019, 15, 1933–1944, doi:10.3762/bjoc.15.189

Graphical Abstract
  • takes place remarkably differs from that in compound 2 and thapsigargin. This is very likely due to stereochemistry on the lactone ring connection at C7 and the absence of a hydroxy group at the same position. The steric circumstances and the presence of the α-carbonyl group makes the tertiary C11
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Published 13 Aug 2019

Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs

  • Juanjuan Feng,
  • Tianyu Li,
  • Jiaxin Zhang and
  • Peng Jiao

Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179

Graphical Abstract
  • gave 16 in 87% yield [26][27]. The absolute stereochemistry of 16 was confirmed by crystal structure analysis [72] and the specific rotation [28] of 17. Centimeter-long prismatic single crystals of 17 were obtained by slow evaporation of a petroleum solution. Starting from 9, we tested several
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Published 01 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
  • 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

The cyclopropylcarbinyl route to γ-silyl carbocations

  • Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

Graphical Abstract
  • isomeric mixture of esters 16. Subsequent reduction with lithium aluminum hydride gave a mixture of alcohols 17 and 18, which could be readily separated by silica gel chromatography. The assignment of stereochemistry of these isomers was based on shielding effects in both 1H and 13C NMR spectra. For
  • . Stereochemistry of the alcohol 58 was established by long-range 19F coupling to the cis-trimethylsilyl group hydrogens (JH-F = 0.9 Hz). Long-range 19F coupling to the TMS methyl groups of 58 was also observed in the 13C NMR spectrum (JC-F = 2.1 Hz) [64][65]. This long-range 19F coupling is not observed when the
  • borohydride reduction of the ester functionality of 63 gave a separable mixture of alcohols 64 and 65. The stereochemistry of the product 65 was established using nOe studies. Cyano to carbomethoxy conversion in 65 to give alcohol 66 was straightforward. Triflate derivatives 67 and 68 were prepared since
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Published 24 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
  • 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
  • diversified biological activity. From several synthetic approaches to ᴅ-ribo-phytosphingosine [79] application of the aziridine aldehyde (2S,1'R)-6 provided (2S,3S,4R)-110 in four steps with full control of stereochemistry (Scheme 29) [80]. Since the 2S absolute configuration of the final product was already
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Published 23 Jul 2019

Synthesis and conformational preferences of short analogues of antifreeze glycopeptides (AFGP)

  • Małgorzata Urbańczyk,
  • Michał Jewgiński,
  • Joanna Krzciuk-Gula,
  • Jerzy Góra,
  • Rafał Latajka and
  • Norbert Sewald

Beilstein J. Org. Chem. 2019, 15, 1581–1591, doi:10.3762/bjoc.15.162

Graphical Abstract
  • conformation of the molecule as well an on the stereochemistry of amino acid residues. The desired monoglycosylated analogues with acetylated amino termini and the carboxy termini in form of N-methylamide have been synthesized. Conformational nuclear magnetic resonance (NMR) studies of the designed analogues
  • have shown a strong influence of the stereochemistry of amino acid residues on the peptide chain stability, which could be connected to the antifreeze activity of these compounds. A better understanding of the mechanism of action of antifreeze glycopeptides would allow applying these materials, e.g
  • the saccharide moiety is conformationally well-defined by the peptide backbone and the whole structure adopts a polyproline II (PP II) helix [17]. Antifreeze activity strongly relies on the stereochemistry of the amino acid residues. Earlier studies have shown that AFGP analogues containing either an
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Published 16 Jul 2019
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