Synthesis of Indoloquinolines: An Intramolecular Cyclization Leading to Advanced Perophoramidine-Relevant Intermediates

The bioactive natural product perophoramidine has proved a challenging synthetic target. An alternative route to its indolo[2,3-b]quinolone core structure involving a N-chlorosuccinimde-mediated intramolecular cyclization reaction is reported. Attempts to progress towards the natural product are also discussed with an unexpected deep-seated rearrangement of the core structure occurring during an attempted iodoetherification reaction. X-ray crystallographic analysis provides important analytical confirmation of assigned structures.

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Synthesis and conformational studies of 9-benzyloxy-18-substituted [3.3]metacyclophanes

Canadian Journal of Chemistry ◽

10.1139/cjc-2015-0174 ◽

2015 ◽

Vol 93 (11) ◽

pp. 1161-1168 ◽

Cited By ~ 9

Author(s):

M. Monarul Islam ◽

Tomiyasu Hirotsugu ◽

Taisuke Matsumoto ◽

Junji Tanaka ◽

Takehiko Yamato

Keyword(s):

Solid State ◽

Intramolecular Cyclization ◽

Acid Treatment ◽

Room Temperature ◽

Coupling Reaction ◽

Chair Conformation ◽

Cyclization Reaction ◽

Conformational Studies ◽

X Ray ◽

H Nmr

A series of syn-[3.3]metacyclophanes (MCPs) containing internal substituted benzyloxy group have been synthesized by the modified TosMIC coupling reaction followed by acid treatment and Wolff–Kishner reduction. anti-Mono- and di-benzyloxy[3.3]MCPs are synthesized by O-benzylation of the corresponding hydroxy[3.3]MCPs, which are obtained by demethylation of methoxy[3.3]MCPs with BBr3 at room temperature. An interesting and intriguing result was obtained when syn-6,15-di-tert-butyl-9-methoxy-18-methyl[3.3]MCP-2,11-dione was treated with TMSI to afford the formation of a dihydrobenzofuran ring by a nucleophilic intramolecular cyclization reaction. The 1H NMR and X-ray analysis of 6a confirms that it adopts a syn (chair–chair) conformation in both solution and solid state.

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Nanostructural analysis of GaN tripods and hexapods grown onc-plane sapphire

Journal of Applied Crystallography ◽

10.1107/s0021889810036472 ◽

2010 ◽

Vol 43 (6) ◽

pp. 1300-1304 ◽

Cited By ~ 3

Author(s):

Sanghwa Lee ◽

Yuri Sohn ◽

Chinkyo Kim ◽

Dong Ryeol Lee ◽

Hyun-Hwi Lee

Keyword(s):

Structural Characteristics ◽

Microscopic Analysis ◽

Crystallographic Analysis ◽

Core Size ◽

X Ray ◽

The Core ◽

Sapphire Substrates ◽

X Ray Scattering ◽

Inversion Domain ◽

Ray Scattering

The crystallographic and structural characteristics of GaN tripods and hexapods grown onc-plane sapphire substrates were investigated using synchrotron X-ray scattering and microscopic analysis. The core structure of a GaN hexapod is revealed to be in the zincblende phase with an inversion domain, and a refined crystallographic analysis of tripods and hexapods with synchrotron X-ray scattering shows the existence of the zincblende phase in wurtzite-based protruding nanorods. The atomistic model combined with this crystallographic analysis reveals that the core size of a hexapod is much smaller than the diameters of the protruding nanorods. This refined structural analysis can be utilized in tailoring the opto-electronic characteristics of GaN multipods.

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Synthesis and structures of 1,3-bis(organochalcogenyl) distannatrisilabicyclo[1.1.1]pentanes

Canadian Journal of Chemistry ◽

10.1139/cjc-2013-0493 ◽

2014 ◽

Vol 92 (6) ◽

pp. 574-579 ◽

Cited By ~ 7

Author(s):

Eric Moos ◽

Timo Augenstein ◽

Delphine Garnier ◽

Frank Breher

Keyword(s):

Nmr Spectroscopy ◽

Single Crystals ◽

Addition Reaction ◽

Core Structure ◽

Coupling Constant ◽

Solid Samples ◽

X Ray ◽

The Core

The heteronuclear [1.1.1]propellane Sn2Si3Mes6 (1; Mes = 2,4,6-Me3C6H2) was reacted with the dichalcogenyl compounds PhE–EPh (E = S, Se, or Te) to furnish the 1,3-bis(organochalcogenyl) distannatrisilabicyclo[1.1.1]pentanes 3 (E = S), 4 (E = Se), and 5 (E = Te). The E–E bond addition reaction is reminiscent of the formation of FcS–Sn(SiMes2)3Sn–SFc (2; Fc = ferrocenyl) reported previously. Contrary to 2, for which it was shown that its formation can be enhanced by daylight, the analogous clusters 3–5 are very sensitive to light in solution. Solid samples are, however, stable for a prolonged period of time. All three compounds were characterized in detail, including X-ray structure analyses on single crystals of 3 and 5. The core structure connectivities of the clusters were fully confirmed by 119Sn, 77Se, and 125Te NMR spectroscopy, among others. In particular, the 117Sn–119Sn coupling constant between the formally nonbonded bridgehead tin atoms nicely correlates with the interbridgehead distance, i.e., a larger distance is associated with a smaller 117Sn–119Sn coupling constant, and vice versa. This coupling is mediated by so-called “back-lobe-to-back-lobe” interactions through cage. The detection of two different 77Se–119Sn and 125Te–119Sn couplings each (i.e., 1J and 2J) further supported these findings.

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Zur strukturellen Verzerrung von Fe4S4I42- -Clustern durch Iod-Iod-Kon Die Kristallstrukturen von (Ph4P)2Fe4S4I4 und (Me3NCH2Ph)2Fe4S4I4 / Structural Distortion of Fe4S4I22- Clusters through Iodine-Iodine Contacts: Crystal Structures of (Ph4P)2Fe4S4I4 and (Me3NCH2Ph)2Fe4S4I4

Zeitschrift für Naturforschung B ◽

10.1515/znb-1988-0412 ◽

1988 ◽

Vol 43 (4) ◽

pp. 457-462 ◽

Cited By ~ 5

Author(s):

Siegfried Pohl ◽

Wolfgang Saak

Keyword(s):

Single Crystal ◽

Crystal Structures ◽

Diffraction Data ◽

Core Structure ◽

Structural Distortion ◽

Monoclinic Space Group ◽

X Ray Diffraction ◽

Space Group ◽

X Ray ◽

The Core

AbstractThe structures of (Ph4P)2Fe4S4I4 (1) and (Me3NCH2Ph)2Fe4S4I4 (2) were determined from single crystal X-ray diffraction data.1 crystallizes in the tetragonal space group I41/a with a = 1088.3(1) and c = 4540.3(2) pm. Z = 4.2: Monoclinic, space group Cc. a = 1332.0(2), b = 1513.8(3), c = 1755.1(3) pm, β = 96.69(1)°, Z = 4.In 1 the anion Fe4S4I42- has imposed S4 symmetry with four short (226.2 pm) and eight long (228.1 and 228.4 pm) Fe-S distances parallel and perpendicular, respectively, to the crystallographic 4̃ axis. The Fe-Fe distances were found to be 274.3 and 275.5 pm (Fe-I 254.1 p0m).In (Me3NCH2Ph)2Fe4S4I4 the [Fe4S4]2+ cluster also exhibits a slightly compressed tetragonal core structure but the core distortions are larger and less regular than in 1 (Fe-S distances from 224.6 to 232.9 pm, Fe-Fe distances from 269.6 to 275.9 pm, Fe-I distances from 249.5 to 255.7 pm).In addition there are in 2 iodine-iodine interactions between the anions with an I-I distance of 391.7 pm. These weak attractive forces seem to be the reason for the rather large and hitherto in [Fe4S4] clusters with four identical ligands unobserved distortion of the Fe4S4 core.

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Origin of the Difference in Phase Transition Behavior between TwoType of All-Organic Radical Liquid Crystals

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.55.42 ◽

2008 ◽

Vol 55 ◽

pp. 42-45

Author(s):

Yoshiaki Uchida ◽

Rui Tamura ◽

Naohiko Ikuma ◽

Satoshi Shimono ◽

Hiroki Takahashi ◽

...

Keyword(s):

Molecular Structure ◽

Phase Transition ◽

Liquid Crystalline ◽

Crystallographic Analysis ◽

Side Chain ◽

Organic Radical ◽

Phase Transition Behavior ◽

X Ray ◽

The Core ◽

The Difference

We have synthesized two types of all-organic radical liquid crystalline (LC) compounds, trans-2-alkoxyphenyl-5-[4-(4-alkoxybenzenecarbonyloxy)phenyl]-2,5-dimethylpyrrolidine-1-oxy (1) and 4-alkoxyphenyl trans-4-[5-(4-alkoxyphenyl)-2,5-dimethylpyrrolidine-1-oxy-2-yl]benzoate (2) and have fully characterized their LC properties. Although the only difference in the molecular structure between 1 and 2 is the orientation of a binding group connecting the core portion and one side-chain (-OCO- and -COO- for 1 and 2), the racemic or enantiomerically enriched 2 showed an SmA phase, or SmA* and TGBA* phases, which were not observed for 1, besides N and SmC, or N* and SmC* phases, respectively. Here we discuss the origin of these differences on the basis of their crystal structures determined by X-ray crystallographic analysis.

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Quaternary structure of Limulus polyphemus hemocyanin

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081747 ◽

1978 ◽

Vol 36 (2) ◽

pp. 176-177

Author(s):

T. Wichertjes ◽

E.J. Kwak ◽

E.F.J. Van Bruggen

Keyword(s):

Electron Microscopy ◽

Functional Properties ◽

Horseshoe Crab ◽

Temperature Jump ◽

Quaternary Structure ◽

Crystallographic Analysis ◽

Limulus Polyphemus ◽

Oxygen Binding ◽

X Ray ◽

Intact Molecule

Hemocyanin of the horseshoe crab (Limulus polyphemus) has been studied in nany ways. Recently the structure, dissociation and reassembly was studied using electron microscopy of negatively stained specimens as the method of investigation. Crystallization of the protein proved to be possible and X-ray crystallographic analysis was started. Also fluorescence properties of the hemocyanin after dialysis against Tris-glycine buffer + 0.01 M EDTA pH 8.9 (so called “stripped” hemocyanin) and its fractions II and V were studied, as well as functional properties of the fractions by NMR. Finally the temperature-jump method was used for assaying the oxygen binding of the dissociating molecule and of preparations of isolated subunits. Nevertheless very little is known about the structure of the intact molecule. Schutter et al. suggested that the molecule possibly consists of two halves, combined in a staggered way, the halves themselves consisting of four subunits arranged in a square.

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Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

10.26434/chemrxiv.12212927 ◽

2020 ◽

Author(s):

Marat Korsik ◽

Edwin Tse ◽

David Smith ◽

William Lewis ◽

Peter J. Rutledge ◽

...

Keyword(s):

Heterocyclic Ring ◽

Ring System ◽

Substitution Reactions ◽

Laboratory Notebook ◽

Polar Solvents ◽

X Ray ◽

X Ray Crystallography ◽

The Core ◽

Nmr Data

We have discovered and studied a telesubstitution reaction in a biologically important heterocyclic ring system. Conditions that favour the tele-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the in vivo active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium. Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds.

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Metal-Free Photoredox-Catalyzed C–H/C–H Coupling of Arenes Enabled by Interrupted Pummerer Activation

10.26434/chemrxiv.9158564 ◽

2019 ◽

Author(s):

Miles Aukland ◽

Mindaugas Šiaučiulis ◽

Adam West ◽

Gregory Perry ◽

David Procter

Keyword(s):

Natural Product ◽

Selective Reduction ◽

Cross Coupling ◽

One Pot ◽

Complex Molecules ◽

Pummerer Reaction ◽

Metal Free ◽

Bond Forming ◽

Coupling Partner ◽

Bioactive Natural Product

Aryl–aryl cross-coupling constitutes one of the most widely used procedures for the synthesis of high-value materials, ranging from pharmaceuticals to organic electronics and conducting polymers. The assembly of (hetero)biaryl scaffolds generally requires multiple steps; coupling partners must be functionalized before the key bond-forming event is considered. Thus, the development of selective C–H arylation processes in arenes, that side-step the need for prefunctionalized partners, is crucial for streamlining the construction of these key architectures. Here we report an expedient, one-pot assembly of (hetero)biaryl motifs using photocatalysis and two non-prefunctionalized arene partners. The approach is underpinned by the activation of a C–H bond in an arene coupling partner using the interrupted Pummerer reaction. A unique pairing of the organic photoredox catalyst and the intermediate dibenzothiophenium salts enables highly selective reduction in the presence of sensitive functionalities. The utility of the metal-free, one-pot strategy is exemplified by the synthesis of a bioactive natural product and the modification of complex molecules of societal importance.

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