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1.
J Med Chem ; 67(2): 1061-1078, 2024 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-38198226

RESUMO

Hedgehog signaling is involved in embryonic development and cancer growth. Functional activity of secreted Hedgehog signaling proteins is dependent on N-terminal palmitoylation, making the palmitoyl transferase Hedgehog acyltransferase (HHAT), a potential drug target and a series of 4,5,6,7-tetrahydrothieno[3,2-c]pyridines have been identified as HHAT inhibitors. Based on structural data, we designed and synthesized 37 new analogues which we profiled alongside 13 previously reported analogues in enzymatic and cellular assays. Our results show that a central amide linkage, a secondary amine, and (R)-configuration at the 4-position of the core are three key factors for inhibitory potency. Several potent analogues with low- or sub-µM IC50 against purified HHAT also inhibit Sonic Hedgehog (SHH) palmitoylation in cells and suppress the SHH signaling pathway. This work identifies IMP-1575 as the most potent cell-active chemical probe for HHAT function, alongside an inactive control enantiomer, providing tool compounds for validation of HHAT as a target in cellular assays.


Assuntos
Proteínas Hedgehog , Proteínas Hedgehog/metabolismo , Piridinas/química , Piridinas/farmacologia
2.
Inorg Chem ; 62(33): 13253-13276, 2023 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-37549423

RESUMO

The synthesis of acylpyrazolone salts and their complexes of main group elements, transition metals, lanthanides, and actinides are described and characterized inter alia by means of single-crystal X-ray crystallography, NMR, and IR spectroscopies. The complexes consist of two, three, or four acylprazolone ligands bound to the metal atom, resulting in a structurally diverse set of coordination complexes with (distorted) octahedral, pentagonal-bipyramidal, or antiprismatic arrangements. Several complexes proved to be polymeric in the solid state including heterobimetallic sodium/lanthanide coordination polymers. A selection of the polymeric compounds was analyzed via TG/DTA measurements to establish their stability. The ligands, in turn, were readily synthesized in good yields from commercially available hydrazine hydrochloride salts. These findings demonstrate that acylpyrazolone ligands can form complexes with metals of varying ionic radii, highlighted by their utility in other areas such as analytical and metal organic framework chemistry.

3.
J Org Chem ; 88(14): 9853-9869, 2023 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-37432502

RESUMO

Triarylsilanols have been reported as the first silicon-centered molecular catalysts for direct amidation of carboxylic acids with amines as identified after a screen of silanols, silanediols, disiloxanediols, and incompletely condensed silsesquioxanes as potential homogeneous catalysts. Subsequent synthesis and testing of various electronically differentiated triarylsilanols have identified tris(p-haloaryl)silanols as more active than the parent triarylsilanol, where the bromide congener is found to be the most active. Catalyst decomposition can be observed by NMR methods, but RPKA methods reveal that product inhibition is operative, where tertiary amides are more inhibitory than secondary amides. Studies using an authentically synthesized triaryl silylester as a putative intermediate in the catalytic system enable a plausible mechanism to be proposed as supported by computationals.

4.
Angew Chem Int Ed Engl ; 62(39): e202304246, 2023 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-37232421

RESUMO

A general approach to 3-azabicyclo[3.1.1]heptanes by reduction of spirocyclic oxetanyl nitriles was developed. The mechanism, scope, and scalability of this transformation were studied. The core was incorporated into the structure of the antihistamine drug Rupatidine instead of the pyridine ring, which led to a dramatic improvement in physicochemical properties.

5.
Org Lett ; 24(49): 8931-8935, 2022 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-36331529

RESUMO

An efficient two-step procedure for the syntheses of pyrimidine nucleosides is presented. A series of glycosyl 5-(aminomethylene)-1,3-dioxane-4,6-dione derivatives were prepared from ß-anomeric isonitriles by reaction with Meldrum's acid or by allowing aminomethylene Meldrum's acid to react with an 1-aldofuranosyl halide or acetate. The resultant 5-(aminomethylene)-1,3-dioxane-4,6-dione derivatives underwent reaction with benzyl- or 2,4-dimethoxybenzyl isocyanate via transacylation to provide uridine-5-carboxylic acid derivatives and related nucleosides. These nucleoside carboxylic acids were converted into other C-5 derivatives by bromo-decarboxylation with N-bromosuccinimide.


Assuntos
Dioxanos , Nucleosídeos de Pirimidina , Uridina , Nucleosídeos
6.
J Nat Prod ; 85(11): 2650-2655, 2022 11 25.
Artigo em Inglês | MEDLINE | ID: mdl-36288514

RESUMO

We report an improved total synthesis of 4,5-dibromo-9,10-dihydrophenanthrene-2,3,6,7-tetraol, (±)-polysiphenol, via intermolecular McMurray dimerization of 5-bromovanillin and subsequent intramolecular oxidative coupling as the key steps. The synthetic route is applicable to 4,5-dichloro- and 4,5-difluoro-halologues (as well as a 4,5-dialkyl-analogue). Distinctive AA'BB' multiplets in their 1H NMR spectra for the dimethylene bridges of the dibromo and dichloro compounds reveal them to be room-temperature stable atropisomers, while for the difluoro compound they present as a singlet. X-ray crystal structure determinations of their tetramethylated synthetic precursors show atropisomeric twist angles of 48°, 46°, and 32°, respectively, with the former representing the largest yet observed in any 4,5-disubstituted-9,10-dihydrophenanthrene. DFT computational studies reveal an unprecedented two-stage atropisomeric interconversion process involving time-independent asynchronous rotations of the dimethylene bridge and the biaryl axis for halologues containing chlorine or bromine, but a more synchronous rotation for the difluoro analogue.


Assuntos
Fenantrenos , Bromo/química , Dimerização , Espectroscopia de Ressonância Magnética , Fenantrenos/química
7.
Phys Chem Chem Phys ; 24(42): 25816-25821, 2022 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-36278412

RESUMO

Following the recent report of the chemical generation and trapping at room temperatures of C2, generated from an alkynyl phenyl iodonium salt, a computational analysis had indicated that both unimolecular fragmentation and bimolecular substitution mechanisms for the process could be envisaged. Here a combined theoretical and experimental analysis explores how the energetics of these mechanisms and resulting experimental products respond to variation in the nucleofuge. When the phenyl iodonium nucleofuge is replaced by pyridinium, trapping products are again obtained, which we conclude favours a bimolecular mechanism involving no free C2. Trapped products in greater yield were also observed using dibenzothiophenium as the nucleofuge in both condensed solution phase and most significantly in a two-flask room temperature experiment in which a volatile species, presumed to be C2, is transferred and trapped in a second flask. The energetics of the unimolecular fragmentation process producing C2 are predicted to be too high to correspond to a facile thermal reaction, which means that an experimental/theoretical dichotomy remains to be explained.

8.
Phys Chem Chem Phys ; 24(34): 20409-20425, 2022 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-35983846

RESUMO

We report the evaluation of density-functional-theory (DFT) based procedures for predicting 19F NMR chemical shifts at modest computational cost for a range of molecules with fluorine bonds, to be used as a tool for assisting the characterisation of reaction intermediates and products and as an aid to identifying mechanistic pathways. The results for a balanced learning set of molecules were then checked using two further testing sets, resulting in the recommendation of the ωB97XD/aug-cc-pvdz DFT method and basis set as having the best combination of accuracy and computational time, with a RMS error of 3.57 ppm. Cationic molecules calculated without counter-anion showed normal errors, whilst anionic molecules showed somewhat larger errors. The method was applied to the prediction of the conformationally averaged 19F chemical shifts of 2,2,3,3,4,4,5,5-octafluoropentan-1-ol, in which gauche stereoelectronic effects involving fluorine dominate and to determining the position of coordination equilibria of fluorinated boranes as an aid to verifying the relative energies of intermediate species involved in catalytic amidation reactions involving boron catalysts.


Assuntos
Boro , Flúor , Carbono , Catálise , Flúor/química , Espectroscopia de Ressonância Magnética/métodos
9.
Chem Commun (Camb) ; 58(32): 4981-4984, 2022 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-35322841

RESUMO

The experimentally determined stereochemical outcome of an unprecedented hydride transfer from a lithium alkoxide to an aldehyde is reported, as deconvoluted by the combined use of a single enantiomer alkoxide in conjunction with a deuterium label. The stereoselective outcome is consistent with a computationally predicted transition state model stabilised by contributions from attractive dispersion forces.


Assuntos
Estereoisomerismo
11.
Magn Reson Chem ; 60(1): 93-103, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34106480

RESUMO

The lack of machine-readable data is a major obstacle in the application of nuclear magnetic resonance (NMR) in artificial intelligence (AI). As a way to overcome this, a procedure for capturing primary NMR spectroscopic instrumental data annotated with rich metadata and publication in a Findable, Accessible, Interoperable and Reusable (FAIR) data repository is described as part of an undergraduate student laboratory experiment in a chemistry department. This couples the techniques of chemical synthesis of a never before made organic ester with illustration of modern data management practices and serves to raise student awareness of how FAIR data might improve research quality and replicability. Searches of the registered metadata are shown, which enable actionable finding and accessing of such data. The potential for re-use of the data in AI applications is discussed.

12.
Phys Chem Chem Phys ; 23(22): 12630-12636, 2021 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-34031672

RESUMO

Recent lively debates about the nature of the quadruple bonding in the diatomic species C2 have been heightened by recent suggestions of molecules in which carbon may be similarly bonded to other elements. The desirability of having methods for generating such species at ambient temperatures and in solution in order to study their properties may have been realized by a recent report of the first chemical synthesis of free C2 itself under mild conditions. The method involved unimolecular fragmentation of an alkynyl zwitterion 2 as generated from the precursor 1, resulting in production and then trapping of free C2 at ambient temperatures rather than the high temperature gas phase methods normally employed for C2 generation. Here, alternative mechanisms are proposed for this reaction based on DFT calculations involving bimolecular 1,1- or 1,2-iodobenzene displacement reactions from 2 directly by galvinoxyl radical, or hydride transfer from 9,10-dihydroanthracene to 2. These mechanisms result in the same trapped products as observed experimentally, but unlike that involving unimolecular generation of free C2, exhibit calculated free energy barriers commensurate with the reaction times observed at room temperatures. The relative energies of the transition states for 1,1 vs. 1,2 substitution provide a rationalisation for the observed isotopic substitution patterns. The same mechanism also provides an energetically facile path to polymeric synthesis of carbon rich species by extending the carbon chain attached to the iodonium group, eventually resulting in formation of amorphous carbon and discrete molecules such as C60.

13.
14.
J Org Chem ; 86(5): 4326-4335, 2021 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-33567827

RESUMO

Downstream intermediates are crucial for the reactivity and selectivity of aminocatalytic reactions. We present an analysis of the stereopreference in aminocatalytic downstream intermediates, which reveals an inconspicuous mechanism of chiral recognition between the catalyst and the rest of the molecule. We delineate a stereoelectronic model to rationalize the mode of chiral transmission. We also exploit it for the resolution of chiral lactols relevant in organic synthesis as well as in the flavor and fragrance industry.

15.
Chem Commun (Camb) ; 56(88): 13567-13570, 2020 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-33151206

RESUMO

DFT computations (ωB97X-D/6-31G(d)) of eight different cycloparaphenylenes that have three internal linking groups are shown to have two different conformations that express interesting Möbius topologies. The D3 conformers have linking numbers Lk of 3 (three half-twists as a trefoil), and the much more stable C2 conformers have a single half-twist, Lk = 1.

16.
Angew Chem Int Ed Engl ; 59(35): 15087-15092, 2020 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-32407571

RESUMO

Main group analogues of cyclobutane-1,3-diyls are fascinating due to their unique reactivity and electronic properties. So far only heteronuclear examples have been isolated. Here we report the isolation and characterization of all-silicon 1,3-cyclobutanediyls as stable closed-shell singlet species from the reversible reactions of cyclotrisilene c-Si3 Tip4 (Tip=2,4,6-triisopropylphenyl) with the N-heterocyclic silylenes c-[(CR2 CH2 )(NtBu)2 ]Si: (R=H or methyl) with saturated backbones. At elevated temperatures, tetrasilacyclobutenes are obtained from these equilibrium mixtures. The corresponding reaction with the unsaturated N-heterocyclic silylene c-(CH)2 (NtBu)2 Si: proceeds directly to the corresponding tetrasilacyclobutene without detection of the assumed 1,3-cyclobutanediyl intermediate.

17.
ChemistryOpen ; 8(10): 1244-1250, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31592408

RESUMO

Using the intrinsic bond orbital (IBO) analysis based on accurate quantum mechanical calculations of the reaction path for the epoxidation of propene using peroxyacetic acid, we find that the four commonly used curly arrows for representing this reaction mechanism are insufficient and that seven curly arrows are required as a result of changes to σ and π bonding interactions, which are usually neglected in all textbook curly arrow representations. The IBO method provides a convenient quantitative method for deriving curly arrows in a rational manner rather than the normal ad hoc representations used ubiquitously in teaching organic chemistry.

18.
ACS Omega ; 4(2): 3280-3286, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-31459544

RESUMO

There is an increasing focus on the part of academic institutions, funding agencies, and publishers, if not researchers themselves, on preservation and sharing of research data. Motivations for sharing include research integrity, replicability, and reuse. One of the barriers to publishing data is the extra work involved in preparing data for publication once a journal article and its supporting information have been completed. In this work, a method is described to generate both human and machine-readable supporting information directly from the primary instrumental data files and to generate the metadata to ensure it is published in accordance with findable, accessible, interoperable, and reusable (FAIR) guidelines. Using this approach, both the human readable supporting information and the primary (raw) data can be submitted simultaneously with little extra effort. Although traditionally the data package would be sent to a journal publisher for publication alongside the article, the data package could also be published independently in an institutional FAIR data repository. Workflows are described that store the data packages and generate metadata appropriate for such a repository. The methods both to generate and to publish the data packages have been implemented for NMR data, but the concept is extensible to other types of spectroscopic data as well.

19.
Org Biomol Chem ; 17(15): 3781-3789, 2019 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-30916707

RESUMO

The kinetics and mechanism of concurrent bromo-de-protonation and bromo-de-tert-butylation of 1,3,5-tri-tert-butylbenzene at different bromine concentrations were studied experimentally and theoretically. Both reactions have high order in bromine (experimental kinetic orders ∼5 and ∼7, respectively). According to quantum chemical DFT calculations, such high reaction orders are caused by participation of clustered polybromide anions Br2n-1- in transition states. Bromo-de-tert-butylation has a higher order due to its bigger reaction center demanding clusters of extended size. A significant primary deuterium kinetic isotope effect (KIE) for bromo-de-protonation is measured indicating proton removal is rate limiting, as confirmed by computed DFT models. The latter predict a larger value for the KIE than measured and possible explanations for this are discussed.

20.
Chem Commun (Camb) ; 55(20): 2916-2919, 2019 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-30785133

RESUMO

An efficient heterogeneous amidation catalyst has been prepared by co-polymerisation of styrene, DVB with 4-styreneboronic acid, which shows wide substrate applicability and higher reactivity than the equivalent homogeneous phenylboronic acid, suggesting potential cooperative catalytic effects. The catalyst can be easily recovered and reused; suitable for use in packed bed flow reactors.

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