Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

Dominika Krištofíková,
Juraj Filo,
Mária Mečiarová and
Radovan Šebesta

Full Research Paper
Published 10 Dec 2019

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1. Graphical Abstract
2. Scheme 1: Ireland–Claisen rearrangement of allyl esters 1a–c.
  
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3. Scheme 2: Ireland–Claisen rearrangement of 1c mediated by tertiary amines.
  
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4. Figure 1: Organocatalysts used in this study. Conditions: typical procedure: 1. Et₃N (4.9 equiv), DCM, −60 °C...
  
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5. Scheme 3: Solvent-free Ireland–Claisen rearrangement of cinnamyl esters.
  
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6. Figure 2: ωB97X-D/6-31G* calculated uncatalyzed Ireland–Claisen rearrangement of 1c. Charges on allylic oxyge...
  
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7. Figure 3: ωB97X-D/6-31G* calculated Schreiner thiourea (12)-catalyzed Ireland–Claisen rearrangement of 1c. Ch...
  
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8. Figure 4: ωB97X-D/6-31G* calculated Ph-thiourea (top) and squaramide-catalyzed (bottom) Ireland–Claisen rearr...
  
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9. Figure 5: a) Rate of product formation; b) reaction profile without catalyst determined by ¹H NMR.
  
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Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290

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Two new aromatic polyketides from a sponge-derived Fusarium

Mada Triandala Sibero,
Tao Zhou,
Keisuke Fukaya,
Daisuke Urabe,
Ocky K. Karna Radjasa,
Agus Sabdono,
Agus Trianto and
Yasuhiro Igarashi

Full Research Paper
Published 09 Dec 2019

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1. Graphical Abstract
2. Figure 1: Structures of compounds 1–7.
  
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3. Figure 2: Key HMBC correlations and two possible structures (a and b) for karimunone A (1).
  
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4. Figure 3: Key HMBC correlations for karimunone B (2).
  
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Beilstein J. Org. Chem. 2019, 15, 2941–2947, doi:10.3762/bjoc.15.289

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Automated glycan assembly of arabinomannan oligosaccharides from Mycobacterium tuberculosis

Alonso Pardo-Vargas,
Priya Bharate,
Martina Delbianco and
Peter H. Seeberger

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Published 06 Dec 2019

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1. Graphical Abstract
2. Scheme 1: Schematic representation of AGA for oligomannosides and oligoarabinomannosides using building block...
  
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3. Figure 1: HPLC chromatograms of crude dodecamer 9. a) Results obtained with AGA procedure A. b) Results obtai...
  
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4. Figure 2: Schematic representation of LAM and AM oligomers obtained using AGA.
  
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Beilstein J. Org. Chem. 2019, 15, 2936–2940, doi:10.3762/bjoc.15.288

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A green, economical synthesis of β-ketonitriles and trifunctionalized building blocks from esters and lactones

Daniel P. Pienaar,
Kamogelo R. Butsi,
Amanda L. Rousseau and
Dean Brady

Letter
Published 06 Dec 2019

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1. Graphical Abstract
2. Scheme 1: Proposed retrosynthesis of the free diol 1.
  
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3. Scheme 2: Preparation of O-unprotected, trifunctionalized synthons from lactones.
  
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Beilstein J. Org. Chem. 2019, 15, 2930–2935, doi:10.3762/bjoc.15.287

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Chemical synthesis of tripeptide thioesters for the biotechnological incorporation into the myxobacterial secondary metabolite argyrin via mutasynthesis

David C. B. Siebert,
Roman Sommer,
Domen Pogorevc,
Michael Hoffmann,
Silke C. Wenzel,
Rolf Müller and
Alexander Titz

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Published 05 Dec 2019

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1. Graphical Abstract
2. Figure 1: Chemical structures of naturally occurring argyrins with potent antipseudomonal activity.
  
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3. Figure 2: The biosynthetic pathway for argyrin production in Cystobacter sp. SBCb004 (Arg1, radical SAM-depen...
  
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4. Figure 3: Designed mutasynthons 9–14 for argyrin biosynthesis. Peptides are based on three amino acids and ad...
  
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5. Scheme 1: Synthesis of tripeptide thioesters. Reagents and conditions: (a) SOCl₂, EtOH, 78 °C; (b) IBCF, NMM,...
  
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6. Scheme 2: Improved synthesis of the tripeptide thioester 14. Reagents and conditions: (a) SOCl₂, EtOH, 78 °C;...
  
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7. Figure 4: Analysis of mutasynthon 14 obtained via the convergent synthetic route by HPLC on a HILIC stationar...
  
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Beilstein J. Org. Chem. 2019, 15, 2922–2929, doi:10.3762/bjoc.15.286

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Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

Daniel R. Sutherland,
Nidhi Sharma,
Georgina M. Rosair,
Ifor D. W. Samuel,
Ai-Lan Lee and
Eli Zysman-Colman

Full Research Paper
Published 04 Dec 2019

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1. Graphical Abstract
2. Scheme 1: Mild and direct C–H monofunctionalization of BQ 1: previous [14] and this work.
  
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3. Figure 1: Benzoquinone derivatives synthesized for this study, with the donor in red and the benzoquinone acc...
  
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4. Scheme 2: Synthesis of 2–4 via mild and direct C–H monofunctionalization of BQ (1).
  
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5. Scheme 3: Synthesis of 5 via double Suzuki coupling.
  
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6. Figure 2: Crystal structures of 3 and 4.
  
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7. Figure 3: HOMO/LUMO and S₁/T₁ energies as well as HOMO/LUMO electron density distribution profiles of 2–5.
  
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8. Figure 4: Cyclic voltammograms and differential pulse voltammograms of 2–5 in degassed DCM (scan rate = 100 m...
  
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9. Figure 5: UV–vis absorption spectra of 2–5 in DCM and photoluminescence spectrum of 3 in degassed DCM and in ...
  
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10. Figure 6: Time-resolved PL plots. a) Prompt decay and b) delayed decay curve of 3 in thin film (λ_exc = 378 nm...
  
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Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

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Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

László Orha,
József M. Tukacs,
László Kollár and
László T. Mika

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Published 03 Dec 2019

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1. Graphical Abstract
2. Scheme 1: Palladium-catalyzed Sonogashira cross-coupling of iodobenzene (1a) and phenylacetylene (2a) in ioni...
  
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3. Figure 1: Effect of catalyst precursors used in Sonogashira coupling reaction of iodobenzene (1a, 0.5 mmol) a...
  
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4. Figure 2: Re-use of Pd catalyst for Sonogashira coupling of iodobenzene (1a) and phenylacetylene (2a). Reacti...
  
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Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

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Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

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

Review
Published 29 Nov 2019

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1. Graphical Abstract
2. Figure 1: Examples of bioactive terpenoids.
  
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3. Figure 2: Repetitive electrophilic and nucleophilic functionalities in terpene and type II PKS-derived polyke...
  
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4. Figure 3: Abundance and distribution of bacterial terpene biosynthetic gene clusters as determined by genome ...
  
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5. Figure 4: Terpenoid biosynthesis. Terpenoid biosynthesis is divided into two phases, 1) terpene scaffold gene...
  
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6. Figure 5: Mechanisms for type I, type II, and type II/type I tandem terpene cyclases. a) Tail-to-head class I...
  
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7. Figure 6: Functional TC characterization. a) Different terpenes were produced when hedycaryol (18) synthase a...
  
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8. Figure 7: Selected examples of terpene modification by bacterial CYPs. a) Hydroxylation [89]. b) Carboxylation, h...
  
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9. Figure 8: Off-target effects observed during heterologous expression of terpenoid BGCs. Unexpected oxidation ...
  
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10. Figure 9: TC promiscuity and engineering. a) Spata-13,17-diene (39) synthase (SpS) can take C₁₅ and C₂₅ oligo...
  
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11. Figure 10: Substrate promiscuity and engineering of CYPs. a) Selected examples from using a CYP library to oxi...
  
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12. Figure 11: Engineering of terpenoid pathways. a) Metabolic network of terpenoid biosynthesis. Toxic intermedia...
  
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Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

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Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

Sara Tejera,
Giada Caniglia,
Rosa L. Dorta,
Andrea Favero,
Javier González-Platas and
Jesús T. Vázquez

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Published 28 Nov 2019

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1. Graphical Abstract
2. Scheme 1: Structures of 4-substituted 1-glucopyranosyltriazoles 1a–g and 2a–g [15].
  
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3. Scheme 2: Synthesis of 1,2-cis-/trans-bistriazoles 7a–7g and 8a–8g [15].
  
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4. Scheme 3: Compounds 9 (trans) and 10 (cis) [15].
  
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5. Scheme 4: Synthesis of (1R,2R)- and (1R,2S)-1,2-bis-(4-(4-bromophenyl)-1H-triazol-1-yl)cyclohexane (12 and 14...
  
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6. Figure 1: Tube inversion test: gels formed by compounds 7f, 8f, 10, 12, and 14.
  
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7. Figure 2: SEM images of the xerogels of compounds 7f (DMSO, top left), 8f (DMSO/H₂O, 3:1, v/v, top right), 10...
  
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8. Figure 3: ORTEP representation of the molecular structure of compound 12 (trans configuration) obtained from ...
  
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9. Figure 4: Crystal packing of compound 12 (trans configuration) in DMSO.
  
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10. Figure 5: Crystal packing of 10 (cis configuration) in DMSO/H₂O (1:1, v/v). Colored lines: π–π stacking inter...
  
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11. Figure 6: CD spectra of compound 10 (cis) in DMSO/H₂O (1:2, v/v) in solution (in black) and as gel (in blue).
  
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Beilstein J. Org. Chem. 2019, 15, 2881–2888, doi:10.3762/bjoc.15.282

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Emission and biosynthesis of volatile terpenoids from the plasmodial slime mold Physarum polycephalum

Xinlu Chen,
Tobias G. Köllner,
Wangdan Xiong,
Guo Wei and
Feng Chen

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Published 28 Nov 2019

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1. Graphical Abstract
2. Figure 1: Plasmodia of P. polycephalum emit a mixture of volatiles predominated by terpenoids. A) GC chromato...
  
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3. Figure 2: P. polycephalum contains four terpene synthase genes. A) Multiple sequence alignment of the protein...
  
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4. Figure 3: PpolyTPS1 and PpolyTPS4 have terpene synthase activities. A) GC chromatogram of sesquiterpenes prod...
  
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5. Figure 4: Phylogenetic analysis of PpolyTPSs with TPSs from dictyostelid social amoebae (Dictyostelids), the ...
  
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Beilstein J. Org. Chem. 2019, 15, 2872–2880, doi:10.3762/bjoc.15.281

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