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Article ; Online: Biomimetic synthetic studies on the hicksoane alkaloids

Stephanie Lee / Tilo Söhnel / Jonathan Sperry

Tetrahedron Chem, Vol 9, Iss , Pp 100060- (2024)

1481

Abstract: The hicksoane alkaloids contain an unusual propane-2,2-diamine unit embedded within a 1,3,6-triazocane, the only natural product known to possess this eight-membered heterocycle. Herein, we report the results examining a biosynthesis proposal that this ... ...

Abstract	The hicksoane alkaloids contain an unusual propane-2,2-diamine unit embedded within a 1,3,6-triazocane, the only natural product known to possess this eight-membered heterocycle. Herein, we report the results examining a biosynthesis proposal that this heterocycle emerges from a late-stage reaction of a dipeptide with acetone. Ile-Trp-CONH2 and Trp-Ile-CONH2 dipeptides were trialled as substrates; in both cases, the intermediate iminium ion did not engage with the primary amide to form the triazocane, reacting instead to generate an imidazolidinone and a β-carboline, respectively. The results from this study infer the triazocane present in these alkaloids is unlikely to be biosynthesised by the late-stage reaction of a dipeptide with biogenic acetone.
Keywords	Organic chemistry ; QD241-441
Language	English
Publishing date	2024-03-01T00:00:00Z
Publisher	Elsevier
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Expanding Heteroaromatic and 2-Aminosugar Chemical Space Accessible from the Biopolymer Chitin

Thaís A. Rossa / Jessica C. Neville / Seongmin Paul Jun / Tilo Söhnel / Jonathan Sperry

Chemistry, Vol 5, Iss 135, Pp 1998-

2023 Volume 2008

Abstract: Herein, we report the expansion of chemical space available from chitin, accessible via the biogenic N -platforms 3A5AF, M4A2C, and di-HAF. The biologically active heteroaromatics furo[3,2- d ]pyrimidin-4-one and furo[3,2- d ]pyrimidin-4-amine can be ... ...

Abstract	Herein, we report the expansion of chemical space available from chitin, accessible via the biogenic N -platforms 3A5AF, M4A2C, and di-HAF. The biologically active heteroaromatics furo[3,2- d ]pyrimidin-4-one and furo[3,2- d ]pyrimidin-4-amine can be selectively accessed from 3A5AF and M4A2C, respectively. The chiral pool synthon di-HAF is a viable substrate for Achmatowicz rearrangement, providing streamlined access to 2-aminosugars possessing a versatile hydroxymethyl group at C5.
Keywords	chitin ; crustacean ; waste to value ; biomass ; Haber independence ; nitrogen heterocycles ; Chemistry ; QD1-999
Language	English
Publishing date	2023-09-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Investigations of catalysis of urethane formation using organotin dicarboxylate

Ransi Devendra / Neil R. Edmonds / Tilo Söhnel

Heliyon, Vol 6, Iss 5, Pp e04074- (2020)

2020

Abstract: The reaction mechanism of the urethane formation for both aliphatic and aromatic isocyanates in the presence of organotin dicarboxylate as a catalyst is investigated theoretically and experimentally. Modelling on a dispersion corrected DFT level of ... ...

Abstract	The reaction mechanism of the urethane formation for both aliphatic and aromatic isocyanates in the presence of organotin dicarboxylate as a catalyst is investigated theoretically and experimentally. Modelling on a dispersion corrected DFT level of theory (B3LYP-D3) shows that an alkoxide complex is formed between organotin dicarboxylate and alcohol. This complex is the dominant catalyst for the urethane formation reaction. In this study, the interaction between the alkoxide complex and isocyanate through N-coordination is considered. By using thermochemical data, it is possible to show that aliphatic isocyanates can be more sensitive to the carboxylic ligand content of the organotin compound as a catalyst in urethane formation in non-polar solvents compared to aromatic isocyanates. The interactions of carboxylic acid, which is formed as an intermediate in the catalysis process, with isocyanate and the effects on the catalytic process are also discussed.
Keywords	Inorganic chemistry ; Organic chemistry ; Organotin dicarboxylate ; Computational ; Urethane ; Catalysis ; Science (General) ; Q1-390 ; Social sciences (General) ; H1-99
Subject code	540
Language	English
Publishing date	2020-05-01T00:00:00Z
Publisher	Elsevier
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Catalytic Synthesis of Oligosiloxanes Mediated by an Air Stable Catalyst, (C6F5)3B(OH2)

Kristel M. Rabanzo-Castillo / Vipin B. Kumar / Tilo Söhnel / Erin M. Leitao

Frontiers in Chemistry, Vol

2020 Volume 8

Abstract: The utility of (C6F5)3B(OH2) as catalyst for the simple and environmentally benign synthesis of oligosiloxanes directly from hydrosilanes, is reported. This protocol offers several advantages compared to other methods of synthesizing siloxanes, such as ... ...

Abstract	The utility of (C6F5)3B(OH2) as catalyst for the simple and environmentally benign synthesis of oligosiloxanes directly from hydrosilanes, is reported. This protocol offers several advantages compared to other methods of synthesizing siloxanes, such as mild reaction conditions, low catalyst loading, and a short reaction time with high yields and purity. The considerable H2O-tolerance of (C6F5)3B(OH2) promoted a catalytic route to disiloxanes which showed >99% conversion of three tertiary silanes, Et3SiH, PhMe2SiH, and Ph3SiH. Preliminary data on the synthesis of unsymmetrical disiloxanes (Si-O-Si') suggests that by modifying the reaction conditions and/or using a 1:1 combination of silane to silanol the cross-product can be favored. Intramolecular reactions of disilyl compounds with catalytic (C6F5)3B(OH2) led to the formation of novel bridged siloxanes, containing a Si-O-Si linkage within a cyclic structure, as the major product. Moreover, the reaction conditions enabled recovery and recycling of the catalyst. The catalyst was re-used 5 times and demonstrated excellent conversion for each substrate at 1.0 mol% catalyst loading. This seemingly simple reaction has a rather complicated mechanism. With the hydrosilane (R3SiH) as the sole starting material, the fate of the reaction largely depends on the creation of silanol (R3SiOH) from R3SiH as these two undergo dehydrocoupling to yield a disiloxane product. Generation of the silanol is based on a modified Piers-Rubinsztajn reaction. Once the silanol has been produced, the mechanism involves a series of competitive reactions with multiple catalytically relevant species involving water, silane, and silanol interacting with the Lewis acid and the favored reaction cycle depends on the concentration of various species in solution.
Keywords	siloxane ; lewis acid catalysis ; dehydrocoupling ; catalyst recycling ; silane ; competing mechanisms ; Chemistry ; QD1-999
Subject code	540 ; 660
Language	English
Publishing date	2020-06-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Impact of the Metal Center and Leaving Group on the Anticancer Activity of Organometallic Complexes of Pyridine-2-carbothioamide

Jahanzaib Arshad / Kelvin K. H. Tong / Sanam Movassaghi / Tilo Söhnel / Stephen M. F. Jamieson / Muhammad Hanif / Christian G. Hartinger

Molecules, Vol 26, Iss 4, p

2021 Volume 833

Abstract: Ru II (cym)Cl (cym = η 6 - p -cymene) complexes of pyridinecarbothioamides have shown potential for development as orally active anticancer metallodrugs, underlined by their high selectivity towards plectin as the molecular target. In order to ... ...

Abstract	Ru II (cym)Cl (cym = η 6 - p -cymene) complexes of pyridinecarbothioamides have shown potential for development as orally active anticancer metallodrugs, underlined by their high selectivity towards plectin as the molecular target. In order to investigate the impact of the metal center on the anticancer activity and their physicochemical properties, the Os(cym), Rh- and Ir(Cp) (Cp = pentamethylcyclopentadienyl) analogues of the most promising and orally active compound plecstatin 2 were prepared and characterized by spectroscopic techniques and X-ray diffraction analysis. Dissolution in aqueous medium results in quick ligand exchange reactions; however, over time no further changes in the 1 H NMR spectra were observed. The Rh- and Ir(Cp*) complexes were investigated for their reactions with amino acids, and while they reacted with Cys, no reaction with His was observed. Studies on the in vitro anticancer activity identified the Ru derivatives as the most potent, independent of their halido leaving group, while the Rh derivative was more active than the Ir analogue. This demonstrates that the metal center has a significant impact on the anticancer activity of the compound class.
Keywords	anticancer agents ; bioorganometallics ; metal complexes ; pyridinecarbothioamide ; metallodrugs ; rhodium ; Organic chemistry ; QD241-441
Subject code	540
Language	English
Publishing date	2021-02-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Transmissionsoptimierte Einkristallstrukturbestimmung und elektronische Struktur von Bi3Ni / Transmission-Optimized Single-Crystal Structure Determination and Electronic Structure of Bi3Ni

Ruck, Michael / Tilo Söhnel

Zeitschrift für Naturforschung. 2014 June 2, v. 61, no. 7

2014

Abstract: Crystals of Bi₃Ni were synthesized using iodine as mineralizer. X-ray diffraction on a single-crystal including transmission-optimized measurement and optimized absorption correction (μ(Mo-Kα) = 1302 cm⁻¹) results in a structure model (Pnma; a = 887.96(7) ...

Abstract	Crystals of Bi₃Ni were synthesized using iodine as mineralizer. X-ray diffraction on a single-crystal including transmission-optimized measurement and optimized absorption correction (μ(Mo-Kα) = 1302 cm⁻¹) results in a structure model (Pnma; a = 887.96(7), b = 409.97(3), c = 1147.8(1) pm) with significant deviations in interatomic distances compared with previous data from X-ray and neutron investigations. From quantum chemical calculations and from the structural chemistry of the subhalides related to Bi₃Ni the chemical structure of the intermetallic compound can be derived. In the crystal structure the Ni atoms have a capped trigonal prismatic coordination of Bi atoms with strong bonds Ni-Bi and Ni-Ni. The prisms constitute rods ¹∞ [NiBi₁/₁Bi₆/₃] by sharing the non-capped square faces. The bonding between the intermetallic rods is clearly weaker than inside them, leading to a preservation of this structural fragment in the subhalides of Bi₃Ni. In accordance with the low temperature superconductivity of the compound, its electronic band structure shows steep and flat bands at the Fermi level. DFT and ELF calculations reveal a separation of delocalized conduction electrons inside the prism rods and largely localized valence electrons between them.
Keywords	X-radiation ; X-ray diffraction ; absorption ; crystal structure ; crystals ; electrons ; iodine ; models ; neutrons ; nickel ; prisms ; superconductivity ; temperature
Language	English
Dates of publication	2014-0602
Size	p. 785-791.
Publishing place	Verlag der Zeitschrift für Naturforschung
Document type	Article
ZDB-ID	124635-5
ISSN	0340-5087 ; 0044-3174 ; 0932-0776 ; 0341-0447 ; 0341-0420
ISSN	0340-5087 ; 0044-3174 ; 0932-0776 ; 0341-0447 ; 0341-0420
DOI	10.1515/znb-2006-0703
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Synthetic Strategy Towards Heterodimetallic Half-Sandwich Complexes Based on a Symmetric Ditopic Ligand

Lewis P. M. Green / Tasha R. Steel / Mie Riisom / Muhammad Hanif / Tilo Söhnel / Stephen M. F. Jamieson / L. James Wright / James D. Crowley / Christian G. Hartinger

Frontiers in Chemistry, Vol

2021 Volume 9

Abstract: Multimetallic complexes have been shown in several examples to possess greater anticancer activity than their monometallic counterparts. The increased activity has been attributed to altered modes of action. We herein report the synthesis of a series of ... ...

Abstract	Multimetallic complexes have been shown in several examples to possess greater anticancer activity than their monometallic counterparts. The increased activity has been attributed to altered modes of action. We herein report the synthesis of a series of heterodimetallic compounds based on a ditopic ligand featuring 2-pyridylimine chelating motifs and organometallic half-sandwich moieties. The complexes were characterized by a combination of 1H NMR spectroscopy, electrospray ionization mass spectrometry, elemental analysis and single crystal X-ray diffraction. Investigations into the stability of representative complexes in DMSO-d6 and 10% DMSO-d6/D2O revealed the occurrence of solvent-chlorido ligand exchange. Proliferation assays in four human cancer cell lines showed that the Os-Rh complex possessed minimal activity, while all other complexes were inactive.
Keywords	anticancer activity ; structural characterization ; ligand exchange reactions ; bioorganometallics ; heterodimetallic complexes ; Chemistry ; QD1-999
Subject code	540
Language	English
Publishing date	2021-12-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: High Antiproliferative Activity of Hydroxythiopyridones over Hydroxypyridones and Their Organoruthenium Complexes

Md. Salman Shakil / Shahida Parveen / Zohaib Rana / Fearghal Walsh / Sanam Movassaghi / Tilo Söhnel / Mayur Azam / Muhammad Ashraf Shaheen / Stephen M. F. Jamieson / Muhammad Hanif / Rhonda J. Rosengren / Christian G. Hartinger

Biomedicines, Vol 9, Iss 2, p

2021 Volume 123

Abstract: Hydroxypyr(id)ones are a pharmaceutically important class of compounds that have shown potential in diverse areas of drug discovery. We investigated the 3-hydroxy-4-pyridones 1a – 1c and 3-hydroxy-4-thiopyridones 1d – 1f as well as their Ru(η 6 - p - ... ...

Abstract	Hydroxypyr(id)ones are a pharmaceutically important class of compounds that have shown potential in diverse areas of drug discovery. We investigated the 3-hydroxy-4-pyridones 1a – 1c and 3-hydroxy-4-thiopyridones 1d – 1f as well as their Ru(η 6 - p -cymene)Cl complexes 2a – 2f , and report here the molecular structures of 1b and 1d as determined by X-ray diffraction analysis. Detailed cell biological investigations revealed potent cytotoxic activity, in particular of the 3-hydroxy-4-thiopyridones 1d – 1f , while the Ru complexes of both compound types were less potent, despite still showing antiproliferative activity in the low μM range. The compounds did not modulate the cell cycle distribution of cancer cells but were cytostatic in A549 and cytotoxic in NCI-H522 non-small lung cancer cells, among other effects on cancer cells.
Keywords	3-hydroxy-4-pyridone ; 3-hydroxy-4-thiopyridone ; anticancer agents ; apoptosis ; cytotoxicity ; Ru(arene) complexes ; Biology (General) ; QH301-705.5
Subject code	540
Language	English
Publishing date	2021-01-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Thiourea-Derived Chelating Ligands and Their Organometallic Compounds

Kelvin K. H. Tong / Muhammad Hanif / James H. Lovett / Katja Hummitzsch / Hugh H. Harris / Tilo Söhnel / Stephen M. F. Jamieson / Christian G. Hartinger

Molecules, Vol 25, Iss 3661, p

Investigations into Their Anticancer Activity

2020 Volume 3661

Abstract: Thiones have been investigated as ligands in metal complexes with catalytic and biological activity. We report the synthesis, characterization, and biological evaluation of a series of M II/III complexes of the general formulae [M II (cym)(L)Cl]X (cym = ... ...

Abstract	Thiones have been investigated as ligands in metal complexes with catalytic and biological activity. We report the synthesis, characterization, and biological evaluation of a series of M II/III complexes of the general formulae [M II (cym)(L)Cl]X (cym = η 6 - p -cymene) or [M III (Cp)(L)Cl]X (Cp = η 5 -pentamethylcyclopentadienyl), where X = Cl − or PF 6 − , and L represents heterocyclic derivatives of thiourea. The thiones feature a benzyl-triazolyl pendant and they act as bidentate ligands via N , S -coordination to the metal centers. Several derivatives have been investigated by single-crystal X-ray diffraction analysis. NMR investigations showed a counterion-dependent shift of several protons due to the interaction with the counterions. These NMR investigations were complemented with X-ray diffraction analysis data and the effects of different counterions on the secondary coordination sphere were also investigated by DFT calculations. In biological studies, the Ir benzimidazole derivative was found to accumulate in the cytoplasm and it was the most cytotoxic derivative investigated.
Keywords	bioorganometallics ; cancer chemotherapeutics ; hydrogen bonds ; molecular structures ; thione ligands ; X-ray fluorescence microscopy ; Organic chemistry ; QD241-441
Subject code	333 ; 540
Language	English
Publishing date	2020-08-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Giant fullerene formation through thermal treatment of fullerene soot

Martin, Jacob W / Grant J. McIntosh / Markus Kraft / Rakesh Arul / Reece N. Oosterbeek / Tilo Söhnel

Carbon. 2017 Dec., v. 125

2017

Abstract: Coalescence of fullerenes into giant fullerenes (Cn n > 100) has been observed in the gas phase and inside carbon nanotubes. In this work, we demonstrate the formation of giant fullerenes by heating fullerene soot. Extracting the majority of the magic ... ...

Abstract	Coalescence of fullerenes into giant fullerenes (Cn n > 100) has been observed in the gas phase and inside carbon nanotubes. In this work, we demonstrate the formation of giant fullerenes by heating fullerene soot. Extracting the majority of the magic number fullerenes (C60 and C70) allowed the underlying distribution of fullerenes in the solid state to be measured. Upon heating at 800–1000 °C for 30–60 min under vacuum the mass distribution of fullerenes was found to shift toward larger masses. High resolution electron microscopy was used to compare formation of giant fullerenes by thermal heating and electron beam irradiation, showing the former produced more isolated giant fullerene fragments >1 nm in size. The driving force for coalescence and growth by thermal heating was suggested to be vertex strain at pentagonal sites, providing a route towards the synthesis of fullerenes up to C300.
Keywords	carbon nanotubes ; electron microscopy ; fullerene ; gases ; heat ; heat treatment ; irradiation ; soot
Language	English
Dates of publication	2017-12
Size	p. 132-138.
Publishing place	Elsevier Ltd
Document type	Article
ISSN	0008-6223
DOI	10.1016/j.carbon.2017.09.045
Database	NAL-Catalogue (AGRICOLA)

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