Synthesis and biological evaluation of 1,2-disubsubstituted 4-quinolone analogues of Pseudonocardia sp. natural products

Stephen M. Geddis,
Teodora Coroama,
Suzanne Forrest,
James T. Hodgkinson,
Martin Welch and
David R. Spring

Letter
Published 19 Oct 2018

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1. Graphical Abstract
2. Figure 1: A family of quinolone natural products 1–8, which were first isolated from Pseudonocardia sp. CL384...
  
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3. Scheme 1: Proposed use of the chemistry developed towards the total synthesis of 5 and 6 for generation of na...
  
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4. Scheme 2: Sonagashira coupling of alkynes 10a and 10b with commercially available acid chloride 9 to give yno...
  
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5. Scheme 3: Conjugate addition of primary amines 12a–f with ynones 11a and 11b. ^aFollowing concentration in vac...
  
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6. Scheme 4: Cyclisation of precursors 13 to natural product analogues 14 using palladium- or copper-catalysed c...
  
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7. Scheme 5: Use of an excess of DMEDA in the Cu-catalysed cyclisation of 13bb resulted in the generation of 14bg...
  
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8. Figure 2: Growth of E. coli ESS with time in the presence of 200 μM of each compound. A) Natural product seri...
  
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9. Figure 3: Growth of S. aureus 25923 with time in the presence of 200 μM of each compound. A) Natural product ...
  
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10. Figure 4: OD₅₂₀ (absorption corresponding to pyocyanin) normalised by the culture population (measured by OD₆...
  
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Beilstein J. Org. Chem. 2018, 14, 2680–2688, doi:10.3762/bjoc.14.245

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Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer

Sagnik Sengupta,
Mena Asha Krishnan,
Premansh Dudhe,
Ramesh B. Reddy,
Bishnubasu Giri,
Sudeshna Chattopadhyay and
Venkatesh Chelvam

Full Research Paper
Published 18 Oct 2018

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1. Graphical Abstract
2. Figure 1: (a) Structure of universal nova tag resin, (b) structure of H-L-Cys(Trt)-2-ClTrt resin.
  
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3. Figure 2: (a) PSMA targeted DUPA rhodamine B chelating conjugate 13. (b) Folate receptor targeted pteroate rh...
  
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4. Scheme 1: Synthesis of PSMA tris(tert-butoxy) protected DUPA ligand 4. Reagents and conditions: (a) Triphosge...
  
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5. Scheme 2: Attempted synthesis of PSMA targeted DUPA rhodamine B chelating conjugate 13 using Fmoc-Lys(Mtt/Mmt...
  
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6. Scheme 3: Synthesis of PSMA targeting DUPA rhodamine B chelating conjugate 13. Reagents and conditions: (a) F...
  
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7. Scheme 4: Synthesis of folate receptor targeting pteroate rhodamine B chelating conjugate 17. Reagents and co...
  
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8. Figure 3: (i) and (ix) DIC image of LNCaP cells (PSMA⁺); (ii) binding and internalization of DUPA-rhodamine B...
  
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Beilstein J. Org. Chem. 2018, 14, 2665–2679, doi:10.3762/bjoc.14.244

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Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

Matthew J. Styles and
Helen E. Blackwell

Full Research Paper
Published 17 Oct 2018

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1. Graphical Abstract
2. Figure 1: A) Overview of LuxI/LuxR-type QS. The LuxI-type protein produces the AHL signal. The AHL diffuses o...
  
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3. Figure 2: Overview of SdiA agonism and antagonism single-point screening results in the S. Typhimurium report...
  
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4. Figure 3: Chemical structures of the most potent SdiA agonists. Compound names (except for 11-Az) match those...
  
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5. Figure 4: Chemical structures of the most potent SdiA antagonists. Compound names preceded by letters match t...
  
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6. Figure 5: Dose–response activity curves for OOHL (2) in competition against various concentrations of synthet...
  
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Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

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The design and synthesis of an antibacterial phenothiazine–siderophore conjugate

Abed Tarapdar,
James K. S. Norris,
Oliver Sampson,
Galina Mukamolova and
James T. Hodgkinson

Letter
Published 16 Oct 2018

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1. Graphical Abstract
2. Figure 1: NDH-2 is a validated target for 1 with an MIC of 1.1 µg/mL against M. tuberculosis.
  
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3. Scheme 1: Synthesis of phenothiazine-PEG-amine component.
  
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4. Scheme 2: Synthesis of the azotochelin siderophore component.
  
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5. Scheme 3: Final conjugation and deprotection to yield a phenothiazine siderophore conjugate.
  
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Beilstein J. Org. Chem. 2018, 14, 2646–2650, doi:10.3762/bjoc.14.242

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Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

Christian Schütz and
Martin Empting

Review
Published 15 Oct 2018

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1. Graphical Abstract
2. Figure 1: The four quorum sensing systems in P. aeruginosa las, iqs, rhl, and pqs. Abbreviations: OdDHL, N-(3...
  
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3. Figure 2: Schematic overview of the PQS biosynthesis and involvement of related metabolites and PqsE in virul...
  
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4. Figure 3: Anthranilic acid (1) and derivatives thereof (2–4).
  
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5. Figure 4: Crystal structure of 6-FABA-AMP in complex with PqsA.
  
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6. Figure 5: Structures of substrate mimetic PqsA inhibitors.
  
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7. Figure 6: Structures and characteristics of prominent classes of PqsD inhibitors.
  
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8. Figure 7: Comparison of docking poses of three prototypic PqsD inhibitors: benzamidobenzoic acid derivative 12...
  
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9. Figure 8: Structures and characteristics of hits against PqsD identified through different methods.
  
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10. Figure 9: HHQ and PQS analogues as PqsD inhibitors and chemical probe used for screening.
  
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11. Figure 10: Structure of PqsD-targeting biofilm inhibitor derived from linezolid.
  
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12. Figure 11: Fragment-based PqsE-inhibitors 24–26.
  
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13. Figure 12: PqsE co-crystal structures. (A) native product 2-ABA; (B–D) hit fragments 24–26.
  
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14. Figure 13: Structurally diverse PqsBC-inhibitors 27–30.
  
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15. Figure 14: Native PqsR ligand HHQ (31) which is converted into PQS (32) by PqsH and synthetic inhibitors 33 an...
  
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16. Figure 15: Quinazolinone inhibitor 36 (QZN).
  
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17. Figure 16: Crystal structure of QZN (36) in complex with PqsR^CBD.
  
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18. Figure 17: Structures of best fitting compounds 37–40 obtained from docking studies.
  
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19. Figure 18: Initial hit 21 and optimized compound 42 (M64).
  
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20. Figure 19: Co-crystal structure of M64 (42) with PqsR^LBD.
  
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21. Figure 20: M64 (42) as the starting point for further optimization leading to 43, which was further modified a...
  
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22. Figure 21: Hit fragments from the benzamide (47–48) and oxadiazole class (49–51).
  
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23. Figure 22: Structures of dual inhibitors 52–55.
  
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24. Figure 23: Sulfonyl pyrimidines 56–58 acting as dual PqsD/PqsR inhibitors.
  
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Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

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Transition metal-free oxidative and deoxygenative C–H/C–Li cross-couplings of 2H-imidazole 1-oxides with carboranyl lithium as an efficient synthetic approach to azaheterocyclic carboranes

Lidia A. Smyshliaeva,
Mikhail V. Varaksin,
Pavel A. Slepukhin,
Oleg N. Chupakhin and
Valery N. Charushin

Letter
Published 12 Oct 2018

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1. Graphical Abstract
2. Scheme 1: C–H/C–Li cross-coupling reactions of 2H-imidazole 1-oxides 1a–d and carboranyl lithium 2. The react...
  
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3. Figure 1: The ¹H NMR spectra of 1-(5-(4-bromophenyl)-2-ethyl-2-methyl-2H-imidazol-4-yl)-1,2-dicarba-closo-dod...
  
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4. Figure 2: Fragment of the 2D ¹H–¹³C{¹H} HSQC (a) and HMBC (b) spectra of imidazolyl carborane 5d in CDCl₃ at ...
  
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5. Figure 3: Molecular structure of 5d. Selected bond distances (Å) and angles (deg) for molecule 1: C(3)–C(14),...
  
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Beilstein J. Org. Chem. 2018, 14, 2618–2626, doi:10.3762/bjoc.14.240

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Pathoblockers or antivirulence drugs as a new option for the treatment of bacterial infections

Matthew B. Calvert,
Varsha R. Jumde and
Alexander Titz

Review
Published 11 Oct 2018

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1. Graphical Abstract
2. Figure 1: Mannosides as inhibitors of the lectin FimH from uropathogenic Escherichia coli.
  
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3. Figure 2: Galactosides targeting uropathogenic Escherichia coli FmlH (compounds 8 and 9) and Pseudomonas aeru...
  
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4. Figure 3: Mannosides and fucosides as inhibitors of P. aeruginosa LecB.
  
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5. Figure 4: β-Cyclodextrin-based antitoxin 19 against S. aureus α-hemolysin and the decavalent Shiga toxin inhi...
  
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6. Figure 5: The mechanism of quorum sensing and representative signaling molecules.
  
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7. Figure 6: Inhibitors of bacterial quorum sensing.
  
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Beilstein J. Org. Chem. 2018, 14, 2607–2617, doi:10.3762/bjoc.14.239

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Synthesis of functionalised β-keto amides by aminoacylation/domino fragmentation of β-enamino amides

Pavel Yanev and
Plamen Angelov

Full Research Paper
Published 10 Oct 2018

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1. Graphical Abstract
2. Scheme 1: Preparation of α-C-acylated β-enamino amides 3 and 4. Reagents and conditions: 2, NMM, EtOCOCl, CH₂...
  
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3. Scheme 2: Domino fragmentation of 3 to β-keto amides 5 with competing cyclisation to pyrrolin-4-ones 6. Reage...
  
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4. Scheme 3: Proposed mechanism for the formation of side products 6.
  
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5. Scheme 4: Proposed mechanism for the formation of the target β-keto amides 5.
  
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6. Scheme 5: Reactivity of analogues 9, lacking the auxiliary amino group [34].
  
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7. Scheme 6: Domino fragmentation of compounds 4 (R² = R³ = H) to N-protected ω-amino-β-keto amides 11.
  
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8. Scheme 7: Ring–chain tautomerism in compounds 11b,c,f,j (n = 2) and reduction to the corresponding β-hydroxy ...
  
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Beilstein J. Org. Chem. 2018, 14, 2602–2606, doi:10.3762/bjoc.14.238

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Synthesis of cis-hydrindan-2,4-diones bearing an all-carbon quaternary center by a Danheiser annulation

Gisela V. Saborit,
Carlos Cativiela,
Ana I. Jiménez,
Josep Bonjoch and
Ben Bradshaw

Letter
Published 09 Oct 2018

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1. Graphical Abstract
2. Figure 1: Previous synthetic approaches to 3a-substituted cis-hydrindan-2,4-diones.
  
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3. Scheme 1: Decahydroquinoline 1 as a versatile building block for Lycopodium alkaloid synthesis.
  
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4. Figure 2: Examples of Lycopodium alkaloids synthesized from 3a-substituted hydrindan-2,4-diones.
  
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5. Scheme 2: A de novo approach to 3a-substituted cis-hydrindan-2,4-diones.
  
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6. Scheme 3: Synthesis of enone 4 and the Danheiser annulation. The depicted compounds are all racemic.
  
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7. Scheme 4: Transformation of the vinylsilane moiety to ketone 8.
  
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8. Figure 3: Stereoview of cis-hydrindane 8.
  
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Beilstein J. Org. Chem. 2018, 14, 2597–2601, doi:10.3762/bjoc.14.237

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Microwave-assisted synthesis of biologically relevant steroidal 17-exo-pyrazol-5'-ones from a norpregnene precursor by a side-chain elongation/heterocyclization sequence

Gergő Mótyán,
László Mérai,
Márton Attila Kiss,
Zsuzsanna Schelz,
Izabella Sinka,
István Zupkó and
Éva Frank

Full Research Paper
Published 08 Oct 2018

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1. Graphical Abstract
2. Scheme 1: Multistep synthesis of steroidal β-ketoesters 4 and 4' from pregnenolone acetate (1) and pregnadien...
  
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3. Scheme 2: Cyclization of compound 4 with hydrazine hydrate (5a), phenylhydrazine (5b) and methylhydrazine (5c...
  
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4. Figure 1: ¹H NMR spectra of compound 7f in CDCl₃ (top; # solvent signal) and in DMSO-d₆ (bottom; # solvent si...
  
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Beilstein J. Org. Chem. 2018, 14, 2589–2596, doi:10.3762/bjoc.14.236

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Impact of Pseudomonas aeruginosa quorum sensing signaling molecules on adhesion and inflammatory markers in endothelial cells

Carmen Curutiu,
Florin Iordache,
Veronica Lazar,
Aurelia Magdalena Pisoschi,
Aneta Pop,
Mariana Carmen Chifiriuc and
Alina Maria Hoban

Full Research Paper
Published 05 Oct 2018

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1. Graphical Abstract
2. Figure 1: Graphic representation of the bacterial adherence to inert substrata (A) and biofilms developed aft...
  
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3. Figure 2: Graphic representation of the adherence index to cellular substrata of PAO1 strain treated with 20 ...
  
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4. Figure 3: Fluorescence microscopy images of QSSMs treated euckariote cells, revealing attachment patterns. (C...
  
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5. Figure 4: Flow cytometry assays for inflammatory (IL-1β, IL-6), and adhesion markers (ICAM-1, PECAM-1, P-sele...
  
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6. Figure 5: Expression levels (fold change) in qRT-PCR experiments for IL-1β, IL-6, TNFα, TGFβ, eNOS, VE-cadher...
  
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Beilstein J. Org. Chem. 2018, 14, 2580–2588, doi:10.3762/bjoc.14.235

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Gold-catalyzed post-Ugi alkyne hydroarylation for the synthesis of 2-quinolones

Xiaochen Du,
Jianjun Huang,
Anton A. Nechaev,
Ruwei Yao,
Jing Gong,
Erik V. Van der Eycken,
Olga P. Pereshivko and
Vsevolod A. Peshkov

Full Research Paper
Published 04 Oct 2018

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1. Graphical Abstract
2. Scheme 1: Synthesis of 2-quinolones 2 through intramolecular Friedel–Crafts hydroarylation of N-aryl propargy...
  
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3. Scheme 2: Strategy towards 2-quinolones 8 bearing a branched substituent on the nitrogen atom.
  
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4. Figure 1: Scope of the protocol.
  
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Beilstein J. Org. Chem. 2018, 14, 2572–2579, doi:10.3762/bjoc.14.234

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Carbonylonium ions: the onium ions of the carbonyl group

Daniel Blanco-Ania and
Floris P. J. T. Rutjes

Commentary
Published 04 Oct 2018

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1. Graphical Abstract
2. Figure 1: Protonated (or organylated) carbonyl (1) and hydroxy (or organyloxy) carbenium ion (2): two possibl...
  
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3. Scheme 1: Acid-catalyzed interconversion of carbonyls, hydrates, hemiacetals and acetals.
  
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4. Figure 2: Oxacarbenium, oxocarbenium, oxycarbenium and carboxonium ions.
  
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Beilstein J. Org. Chem. 2018, 14, 2568–2571, doi:10.3762/bjoc.14.233

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Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

Keishiro Tahara,
Ling Pan,
Toshikazu Ono and
Yoshio Hisaeda

Review
Published 02 Oct 2018

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1. Graphical Abstract
2. Figure 1: (a) Structure and (b) reactivity of B₁₂.
  
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3. Figure 2: (a) Schematic representation of B₁₂ enzyme-involving systems. (b) Construction of biomimetic and bi...
  
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4. Scheme 1: (a) Carbon-skeleton rearrangement mediated by a coenzyme B₁₂-depenedent enzyme. (b) Electrochemical...
  
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5. Scheme 2: Electrochemical carbon-skeleton arrangements mediated by B₁₂ model complexes.
  
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6. Figure 3: Key electrochemical reactivity of 1 and 2 in methylated forms.
  
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7. Scheme 3: Carbon-skeleton arrangements mediated by B₁₂-vesicle artificial enzymes.
  
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8. Scheme 4: Carbon-skeleton arrangements mediated by B₁₂-HSA artificial enzymes.
  
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9. Scheme 5: Photochemical carbon-skeleton arrangements mediated by B₁₂-Ru@MOF.
  
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10. Scheme 6: (a) Methyl transfer reaction mediated by B₁₂-dependent methionine synthase. (b) Methyl transfer rea...
  
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11. Scheme 7: Methyl transfer reaction for the detoxification of inorganic arsenics.
  
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12. Scheme 8: (a) Dechlorination of 1,1,2,2-tetrarchloroethene mediated by a reductive dehalogenase. (b) Electroc...
  
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13. Scheme 9: Visible-light-driven dechlorination of DDT using 1 in the presence of photosensitizers.
  
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14. Scheme 10: 1,2-Migration of a phenyl group mediated by the visible-light-driven catalytic system composed of 1...
  
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15. Scheme 11: Ring-expansion reactions mediated by the B₁₂-TiO₂ hybrid catalyst with UV-light irradiation.
  
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16. Scheme 12: Trifluoromethylation and perfluoroalkylation of aromatic compounds achieved through electrolysis wi...
  
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Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

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Synthesis of 3-aminocoumarin-N-benzylpyridinium conjugates with nanomolar inhibitory activity against acetylcholinesterase

Nisachon Khunnawutmanotham,
Cherdchai Laongthipparos,
Patchreenart Saparpakorn,
Nitirat Chimnoi and
Supanna Techasakul

Full Research Paper
Published 02 Oct 2018

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1. Graphical Abstract
2. Figure 1: Design of the target compounds.
  
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3. Scheme 1: Synthesis of 3-aminocoumarin-N-benzylpyridinium salts.
  
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4. Figure 2: Docked conformations of donepezil (ball-and-stick model; pink), compounds 9a, 9b, 9e, 9h, and 9i (s...
  
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5. Figure 3: Binding interactions in the rhAChE binding pocket with (a) 4a, (b) 9a, (c) 9b, (d) 9e, (e) 9h, (f) ...
  
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Beilstein J. Org. Chem. 2018, 14, 2545–2552, doi:10.3762/bjoc.14.231

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Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

Sambasivarao Kotha,
Saidulu Todeti and
Vikas R. Aswar

Full Research Paper
Published 01 Oct 2018

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1. Graphical Abstract
2. Figure 1: Various alkaloids containing propellane frame work.
  
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3. Scheme 1: Synthesis of the star-shaped norbornene derivative 11 via trimerization.
  
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4. Figure 2: Selected list of ruthenium-based catalysts used for ROM.
  
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5. Scheme 2: Synthesis of the C₃-symmetric molecule 15 bearing propellane moieties via trimerization and RCM.
  
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6. Scheme 3: Synthesis of C₃-symmetric molecule 21 bearing propellane moieties via trimerization and RCM.
  
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Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

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Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

Nicholas G. Jentsch,
Jared D. Hume,
Emily B. Crull,
Samer M. Beauti,
Amy H. Pham,
Julie A. Pigza,
Jacques J. Kessl and
Matthew G. Donahue

Full Research Paper
Published 28 Sep 2018

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1. Graphical Abstract
2. Figure 1: Investigational non-catalytic HIV-1 Integrase inhibitors.
  
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3. Scheme 1: Boehringer Ingelheim retrosynthesis of quinoline 1.
  
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4. Scheme 2: Quinoline ring condensation strategies.
  
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5. Scheme 3: Isatoic anhydrides from anthranilic acids with triphosgene.
  
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6. Scheme 4: Substituted 2-methyl-4-hydroxyquinolines from isatoic anhydrides and ethyl acetoacetate.
  
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7. Scheme 5: Mechanistic hypothesis for the cyclocondensation reaction.
  
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8. Scheme 6: Quinoline synthesis with ethyl acetylpyruvate.
  
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9. Scheme 7: Elaboration of the benzoic acid ethyl ester to the acetic acid residue.
  
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10. Scheme 8: Umpolung addition of ethoxycarbonyl via a MAC strategy.
  
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Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

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Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

Amrita Das,
Mitasree Maity,
Simon Malcherek,
Burkhard König and
Julia Rehbein

Full Research Paper
Published 27 Sep 2018

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1. Graphical Abstract
2. Figure 1: Selected examples of sulfenylated heterocycles used in pharmaceuticals and material chemistry.
  
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3. Scheme 1: Synthetic routes to organosulfur compounds.
  
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4. Scheme 2: Aryl sulfide synthesis.
  
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5. Scheme 3: Substrate scope for arylthiol syntheses. The reaction was performed with 1a–g (0.1 mmol) and 2a–d (...
  
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6. Figure 2: Crystal structures of compounds 3a, 3d, 3e and 3i.
  
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7. Scheme 4: Radical trapping experiments.
  
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8. Figure 3: (a) Changes in the fluorescence spectra (in this case intensity, λ_Ex = 455 nm) of [Ir(dF(CF₃)ppy)₂(...
  
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9. Scheme 5: Proposed mechanism for visible light mediated direct C–H sulfenylation.
  
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10. Figure 4: Black line: UV–vis spectrum of the degassed [Ir] + 1,3,5-TMB mixture (solution A) in ACN. Blue and ...
  
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Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

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Synthesis of dihydroquinazolines from 2-aminobenzylamine: N³-aryl derivatives with electron-withdrawing groups

Nadia Gruber,
Jimena E. Díaz and
Liliana R. Orelli

Full Research Paper
Published 26 Sep 2018

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1. Graphical Abstract
2. Figure 1: N-Aryl-3,4-dihydroquinazolines 1.
  
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3. Scheme 1: Synthetic pathway leading to N-aryl-3,4-dihydroquinazolines 1.
  
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4. Scheme 2: Synthesis of compounds 2.
  
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5. Figure 2: Reaction intermediate in the synthesis of compound 2a.
  
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6. Scheme 3: Addition–elimination mechanism for the heterocyclization.
  
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7. Scheme 4: Proposed mechanism involving an intermediate nitrilium ion.
  
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Beilstein J. Org. Chem. 2018, 14, 2510–2519, doi:10.3762/bjoc.14.227

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Comparative cell biological study of in vitro antitumor and antimetastatic activity on melanoma cells of GnRH-III-containing conjugates modified with short-chain fatty acids

Eszter Lajkó,
Sarah Spring,
Rózsa Hegedüs,
Beáta Biri-Kovács,
Sven Ingebrandt,
Gábor Mező and
László Kőhidai

Full Research Paper
Published 26 Sep 2018

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1. Graphical Abstract
2. Figure 1: Schematic structure of Dau-conjugated GnRH-III or its derivatives containing ⁴Lys with acetyl or bu...
  
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3. Figure 2: Cellular uptake of Dau–GnRH-III conjugates and free daunorubicin (Dau) by A2058 cells. Cellular upt...
  
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4. Figure 3: Short-term growth inhibitory effects of the conjugates and daunorubicin (Dau) on A2058 cells. The m...
  
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5. Figure 4: Effects of conjugates and daunorubicin (Dau) on cell cycle progression of A2058 melanoma cells. The...
  
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6. Figure 5: Effects of the conjugates and daunorubicin (Dau) on melanoma cell adhesion. The Delta CI (Delta Cel...
  
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7. Figure 6: Chemotactic effects of Dau–GnRH-III conjugates on A2058 cell line. The ‘Chemotaxis index’ (Chtx. in...
  
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8. Figure 7: Effects of GnRH-III(Dau=Aoa) (a–c), [⁴Lys(Ac)]-GnRH-III(Dau=Aoa) (d–f) and [⁴Lys(Bu)]-GnRH-III(Dau=...
  
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9. Figure 8: Schematic representation of the proposed mechanisms of the effects of GnRH-III conjugates containin...
  
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Beilstein J. Org. Chem. 2018, 14, 2495–2509, doi:10.3762/bjoc.14.226

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Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

Paris E. Georghiou,
Shofiur Rahman,
Abdullah Alodhayb,
Hidetaka Nishimura,
Jaehyun Lee,
Atsushi Wakamiya and
Lawrence T. Scott

Full Research Paper
Published 25 Sep 2018

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1. Graphical Abstract
2. Figure 1: Examples of calix[n]arenes 1 and calix[4]azulenes 2–5.
  
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3. Figure 2: Three major computed conformers of OPC4A; a: 1,2-alternate; b: cone and c: saddle.
  
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4. Figure 3: Geometry-optimized (ωB97xD/6-31G(d)) and (ωB97xD/GenECP) structures, respectively, computed for lef...
  
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Beilstein J. Org. Chem. 2018, 14, 2488–2494, doi:10.3762/bjoc.14.225

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Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

Luce Mattio,
Loana Musso,
Leonardo Scaglioni,
Andrea Pinto,
Piera Anna Martino and
Sabrina Dallavalle

Letter
Published 24 Sep 2018

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1. Graphical Abstract
2. Figure 1: Structures of leopolic acid A and compound 1.
  
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3. Scheme 1: Synthesis of 3-decyltetramic intermediate 13. Reagent and conditions: a) TEA, THF, 0 °C to rt, 2.5 ...
  
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4. Scheme 2: Synthesis of dipeptide L-Phe-L-Val intermediate 20. Reagents and conditions: a) PTSA·H₂O, benzyl al...
  
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5. Scheme 3: Synthesis of compound 1. Reagents and conditions: a) n-BuLi, THF, −60 °C, 220 min, 60%; b) H₂, Pd/C...
  
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Beilstein J. Org. Chem. 2018, 14, 2482–2487, doi:10.3762/bjoc.14.224

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Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

Sambasivarao Kotha,
Milind Meshram and
Chandravathi Chakkapalli

Review
Published 21 Sep 2018

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1. Graphical Abstract
2. Figure 1: Various catalysts used for metathesis reactions.
  
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3. Scheme 1: SM coupling and RCM protocol to substituted indene derivative 10.
  
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4. Scheme 2: Synthesis of polycycles via SM and RCM approach.
  
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5. Figure 2: Various angucyclines.
  
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6. Scheme 3: SM coupling and RCM protocol to the benz[a]anthracene skeleton 26.
  
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7. Scheme 4: Synthesis of substituted spirocycles via RCM and SM sequence.
  
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8. Scheme 5: Synthesis of highly functionalized bis-spirocyclic derivative 37.
  
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9. Scheme 6: Synthesis of spirofluorene derivatives via RCM and SM coupling sequence.
  
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10. Scheme 7: Synthesis of truxene derivatives via RCM and SM coupling.
  
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11. Scheme 8: Synthesis of substituted isoquinoline derivative via SM and RCM protocol.
  
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12. Scheme 9: Synthesis to 8-aryl substituted coumarin 64 via RCM and SM sequence.
  
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13. Scheme 10: Synthesis of cyclic sulfoximine 70 via SM and RCM as key steps.
  
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14. Scheme 11: Synthesis of 1-benzazepine derivative 75 via SM and RCM as key steps.
  
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15. Scheme 12: Synthesis of naphthoxepine derivative 79 via RCM followed by SM coupling.
  
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16. Scheme 13: Sequential CM and SM coupling approach to Z-stilbene derivative 85.
  
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17. Scheme 14: Synthesis of substituted trans-stilbene derivatives via SM coupling and RCM.
  
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18. Scheme 15: Synthesis of biaryl derivatives via sequential EM, DA followed by SM coupling.
  
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19. Scheme 16: Synthesis of the dibenzocyclooctadiene core of schisandrene.
  
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20. Scheme 17: Synthesis of cyclophane 115 via SM coupling and RCM as key steps.
  
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21. Scheme 18: Synthesis of cyclophane 120 and 122 via SM coupling and RCM as key steps.
  
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22. Scheme 19: Synthesis of cyclophanes via SM and RCM.
  
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23. Scheme 20: Synthesis of MK-6325 (141) via RCM and SM coupling.
  
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Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

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Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

Alex Frichert,
Peter G. Jones and
Thomas Lindel

Full Research Paper
Published 20 Sep 2018

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1. Graphical Abstract
2. Figure 1: Bicyclic eunicellane-type diterpenes.
  
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3. Figure 2: Synthetic eunicellane-type compounds with benzene partial structure.
  
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4. Scheme 1: Access to ketoester 14 that did not cyclize to the ethyl vinyl ether under McMurry conditions.
  
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5. Scheme 2: Synthesis of the 1,3-cyclohexadiene-containing eunicellane-type [8.4.0]bicycle 18 by McMurry coupli...
  
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6. Figure 3: Preferred conformations of diastereomeric diols 18 and 19 including decisive NOESY correlations.
  
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7. Scheme 3: Assembly of the envisaged cyclization precursor 27.
  
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8. Scheme 4: Structure analysis of diastereomeric cyanohydrins 29 and 30.
  
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9. Scheme 5: Formation of allenes 32 and 34 from sterically crowded propargylic alcohol 31.
  
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Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

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Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

Tetsuaki Fujihara and
Yasushi Tsuji

Review
Published 19 Sep 2018

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1. Graphical Abstract
2. Scheme 1: Optimization of the Co-catalyzed carboxylation of 1a.
  
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3. Scheme 2: Co-catalyzed carboxylation of propargyl acetates 1.
  
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4. Scheme 3: Plausible reaction mechanism for the Co-catalyzed carboxylation of propargyl acetates 1.
  
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5. Scheme 4: Optimization of the Co-catalyzed carboxylation of 3a.
  
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6. Scheme 5: Co-catalyzed carboxylation of vinyl triflates 3.
  
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7. Scheme 6: Co-catalyzed carboxylation of a sterically hindered aryl triflate 5.
  
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8. Scheme 7: Optimization of the Co-catalyzed carboxylation of 7a.
  
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9. Scheme 8: Scope of the reductive carboxylation of α,β-unsaturated nitriles 7.
  
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10. Scheme 9: Scope of the carboxylation of α,β-unsaturated carboxamides 9.
  
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11. Scheme 10: Optimization of the Co-catalyzed carboxylation of 11a.
  
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12. Scheme 11: Scope of the carboxylation of allylarenes 11.
  
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13. Scheme 12: Scope of the carboxylation of 1,4-diene derivatives 14.
  
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14. Scheme 13: Plausible reaction mechanism for the Co-catalyzed C(sp³)–H carboxylation of allylarenes.
  
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15. Scheme 14: Optimization of the Co-catalyzed carboxyzincation of 16a.
  
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16. Scheme 15: Derivatization of the carboxyzincated product.
  
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17. Scheme 16: Co-catalyzed carboxyzincation of alkynes 16.
  
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18. Scheme 17: Plausible reaction mechanism for the Co-catalyzed carboxyzincation of alkynes 16.
  
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19. Scheme 18: Co-catalyzed four-component coupling of alkynes 16, acrylates 18, CO₂, and zinc.
  
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20. Scheme 19: Proposed reaction mechanism for the Co-catalyzed four-component coupling.
  
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21. Scheme 20: Visible-light-driven hydrocarboxylation of alkynes.
  
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22. Scheme 21: Visible-light-driven synthesis of γ-hydroxybutenolides from ortho-ester-substituted aryl alkynes.
  
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23. Scheme 22: One-pot synthesis of coumarines and 2-quinolones via hydrocarboxylation/alkyne isomerization/cycliz...
  
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24. Scheme 23: Proposed reaction mechanism for the Co-catalyzed carboxylative cyclization of ortho-substituted aro...
  
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25. Scheme 24: Rh-catalyzed carboxylation of arylboronic esters 25.
  
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26. Scheme 25: Rh-catalyzed carboxylation of alkenylboronic esters 27.
  
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27. Scheme 26: Plausible reaction mechanism for the Rh-catalyzed carboxylation of arylboronic esters 25.
  
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28. Scheme 27: Ligand effect on the Rh-catalyzed carboxylation of 2-phenylpyridine 29a.
  
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29. Scheme 28: Rh-catalyzed chelation-assisted C(sp²)–H bond carboxylation with CO₂.
  
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30. Scheme 29: Reaction mechanism for the Rh-catalyzed C(sp²)–H carboxylation of 2-pyridylarenes 29.
  
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31. Scheme 30: Carboxylation of C(sp²)–H bond with CO₂.
  
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32. Scheme 31: Carboxylation of C(sp²)–H bond with CO₂.
  
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33. Scheme 32: Reaction mechanism for the Rh-catalyzed C(sp²)–H carboxylation of 2-arylphenols 34.
  
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34. Scheme 33: Hydrocarboxylation of styrene derivatives with CO₂.
  
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35. Scheme 34: Hydrocarboxylation of α,β-unsaturated esters with CO₂.
  
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36. Scheme 35: Asymmetric hydrocarboxylation of α,β-unsaturated esters with CO₂.
  
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37. Scheme 36: Proposed reaction mechanism for the Rh-catalyzed hydrocarboxylation of C–C double bonds with CO₂.
  
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38. Scheme 37: Visible-light-driven hydrocarboxylation with CO₂.
  
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39. Scheme 38: Visible-light-driven Rh-catalyzed hydrocarboxylation of C–C double bonds with CO₂.
  
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40. Scheme 39: Optimization of reaction conditions on the Rh-catalyzed [2 + 2 + 2] cycloaddition of diyne 42a and ...
  
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41. Scheme 40: [2 + 2 + 2] Cycloaddition of diyne and CO₂.
  
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42. Scheme 41: Proposed reaction pathways for the Rh-catalyzed [2 + 2 + 2] cycloaddition of diyne and CO₂.
  
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Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

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Supporting Information File 1: General procedure, synthesis of the aldol products, spectroscopic data, and copies of ¹H, ¹³C, and ¹⁹F NMR spectra.
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Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ6-sulfanyl)acetic acid esters with aldehydes

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Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ⁶-sulfanyl)acetic acid esters with aldehydes