117 results found
Fuchter MJ, 2020, On the promise of photopharmacology using photoswitches: a medicinal chemist's perspective., Journal of Medicinal Chemistry, ISSN: 0022-2623
Photopharmacology is a growing area of endeavor that employs photoswitchable ligands to allow for light-dependent pharmacological activity. By coupling light to therapeutic action, improved spatial and temporal selectivity can be achieved and subsequently harnessed for new concepts in therapy. Tremendous progress has already been made, with photopharmacological agents now reported against a wide array of target classes, and light-dependent results demonstrated in a range of live cell and animal models. Several challenges remain however, especially in order for photopharmacology to truly impact the clinical management of disease. This perspective aims to summarize these challenges, particularly with attention to the medicinal chemistry that will be unavoidably required for the further translation of these agents/approaches. By clearly defining challenges for drug hunters, it is hoped that further research into the medicinal chemistry of photopharmacological agents will be stimulated; ultimately enabling full realization of the huge potential for this exciting field.
Gerkman MA, Gibson RSL, Calbo J, et al., 2020, Arylazopyrazoles for long-term thermal energy storage and optically-triggered heat release below 0 °C, Journal of the American Chemical Society, Vol: 142, Pages: 8688-8695, ISSN: 0002-7863
Arylazopyrazole derivatives based on four core structures (4pzMe, 3pzH, 4pzH, and 4pzH-F2) and functionalized with a dodecanoate group were demonstrated to store thermal energy in their metastable Z isomer liquid phase and release the energy by optically triggered crystallization at −30 ℃ for the first time. Three heat storage-release schemes were discovered involving different activation methods (optical, thermal, or combined) for generating liquid-state Z isomers capable of storing thermal energy. Visible light irradiation induced the selective crystallization of the liquid phase via Z-to-E isomerization, and the latent heat stored in the liquid Z isomers was preserved for longer than two weeks unless optically triggered. Up to 92 kJ/mol of thermal energy was stored in the compounds demonstrating remarkable thermal stability of Z isomers at high temperatures and liquid-phase stability at temperatures below 0 ℃.
Rueda-Zubiaurre A, Yahiya S, Fischer O, et al., 2020, Structure-activity relationship studies of a novel class of transmission blocking antimalarials targeting male gametes., Journal of Medicinal Chemistry, Vol: 63, Pages: 2240-2262, ISSN: 0022-2623
Malaria is still a leading cause of mortality among children in the developing world, and despite the immense progress made in reducing the global burden, further efforts are needed if eradication is to be achieved. In this context, targeting transmission is widely recognized as a necessary intervention towards that goal. After carrying out a screen to discover new transmission-blocking agents, herein we report our medicinal chemistry efforts to study the potential of the most robust hit, DDD01035881, as a male-gamete targeted compound. We reveal key structural features for the activity of this series and identify analogues with greater potency and improved metabolic stability. We believe this study lays the groundwork for further development of this series as a transmission blocking agent.
Kurz W, Yetisen AK, Kaito MV, et al., 2020, UV-Sensitive Wearable Devices for Colorimetric Monitoring of UV Exposure, ADVANCED OPTICAL MATERIALS, Vol: 8, ISSN: 2195-1071
Calbo J, Thawani AR, Gibson RSL, et al., 2019, A combinatorial approach to improving the performance of azoarene photoswitches, BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY, Vol: 15, Pages: 2753-2764, ISSN: 1860-5397
Wan L, Wade J, Salerno F, et al., 2019, Inverting the handedness of circularly polarized luminescence from light-emitting polymers using film thickness, ACS Nano, Vol: 13, Pages: 8099-8105, ISSN: 1936-0851
The emission of circularly polarized light is central to many applications, including data storage, optical quantum computation, biosensing, environmental monitoring, and display technologies. An emerging method to induce (chiral) circularly polarized (CP) electroluminescence from the active layer of polymer light-emitting diodes (polymer OLEDs; PLEDs) involves blending achiral polymers with chiral small-molecule additives, where the handedness/sign of the CP light is controlled by the absolute stereochemistry of the small molecule. Through the in-depth study of such a system we report an interesting chiroptical property: the ability to tune the sign of CP light as a function of active layer thickness for a fixed enantiomer of the chiral additive. We demonstrate that it is possible to achieve both efficient (4.0 cd/A) and bright (8000 cd/m2) CP-PLEDs, with high dissymmetry of emission of both left-handed (LH) and right-handed (RH) light, depending on thickness (thin films, 110 nm: gEL = 0.51, thick films, 160 nm: gEL = -1.05, with the terms "thick" and "thin" representing the upper and lower limits of the thickness regime studied), for the same additive enantiomer. We propose that this arises due to an interplay between localized CP emission originating from molecular chirality and CP light amplification or inversion through a chiral medium. We link morphological, spectroscopic, and electronic characterization in thin films and devices with theoretical studies in an effort to determine the factors that underpin these observations. Through the control of active layer thickness and device architecture, this study provides insights into the mechanisms that result in CP luminescence and high performance from CP-PLEDs, as well as demonstrating new opportunities in CP photonic device design.
Yahiya S, Rueda-Zubiaurre A, Delves MJ, et al., 2019, The antimalarial screening landscape-looking beyond the asexual blood stage, CURRENT OPINION IN CHEMICAL BIOLOGY, Vol: 50, Pages: 1-9, ISSN: 1367-5931
Gibson R, Calbo J, Fuchter MJ, 2019, Chemical Z‐E isomer switching of arylazopyrazoles using acid, ChemPhotoChem, Vol: 3, Pages: 372-377, ISSN: 2367-0932
Arylazopyrazoles show significant potential as next‐generation photoswitches, in particular because of the high thermal stability of their Z‐isomers. Herein we investigate the potential to perform Z−E isomer chemical switching of arylazopyrazoles using acid. We show that acid‐accelerated isomerisation allows for robust Z−E switching using mild acids and opens up the possibility to use light‐acid cycles to near quantitatively and reversibly switch the arylazopyrazoles at room temperature. We attribute the chemical switching to azonium formation, facilitated by mesomeric stabilisation by the pyrazole ring. Coupled with their exceptionally long Z‐isomer half‐lives, we believe our study may open up a wider array of functional opportunities for the arylazopyrazoles.
Bardell-Cox O, White AJP, Aragón L, et al., 2019, Synthetic studies on the reverse antibiotic natural products, the nybomycins, MedChemComm, Vol: 10, Pages: 1438-1444, ISSN: 2040-2503
Antimicrobial resistance (AMR) is a serious issue that could have severe consequences if steps are not taken. The nybomycin natural products have the potential to extend the clinical efficacy of the marketed fluoroquinolone class of antibiotics through a ‘reverse antibiotic’ approach. However, only very limited structure–activity relationships are known for these fascinating compounds, in part due to challenges with their synthesis. Here we report a new scalable and robust synthetic route to the nybomycin natural products to aid in the development of this series. Through this synthesis, we report the antibiotic activity of novel analogues of this family confirming the selectivity for fluoroquinolone resistant bacteria and potential future opportunities for further optimisation.
Mercea DM, Howlett MG, Piascik AD, et al., 2019, Enantioselective reduction of N-alkyl ketimines with frustrated Lewis pair catalysis using chiral borenium ions, Chemical Communications, Vol: 55, Pages: 7077-7080, ISSN: 1359-7345
Enantioselective reduction of ketimines was demonstrated using chiral N-heterocyclic carbene (NHC)-stabilised borenium ions in frustrated Lewis pair catalysis. High levels of enantioselectivity were achieved for substrates featuring secondary N-alkyl substituents. Comparative reactivity and mechanistic studies identify key determinants required to achieve useful enantioselectivity and represent a step forward in the further development of enantioselective FLP methodologies.
Salerno F, Rice B, Schmidt JA, et al., 2019, The influence of nitrogen position on charge carrier mobility in enantiopure azahelicene crystals, Physical Chemistry Chemical Physics, Vol: 21, Pages: 5059-5067, ISSN: 1463-9076
The properties of an organic semiconductor are dependent on both the chemical structure of the molecule involved, and how it is arranged in the solid-state. It is challenging to extract the influence of each individual factor, as small changes in the molecular structure often dramatically change the crystal packing and hence solid-state structure. Here, we use calculations to explore the influence of the nitrogen position on the charge mobility of a chiral organic molecule when the crystal packing is kept constant. The transfer integrals for a series of enantiopure azahelicene crystals sharing the same packing were analysed in order to identify the best supramolecular motifs to promote charge carrier mobility. The regioisomers considered differ only in the positioning of the nitrogen atom in the aromatic scaffold. The simulations showed that even this small change in the chemical structure has a strong effect on the charge transport in the crystal, leading to differences in charge mobility of up to one order of magnitude. Some azahelicene isomers that were packed interlocked with each other showed high HOMO-HOMO integrals (up to 70 meV), whilst molecules arranged with translational symmetry generally afforded the highest LUMO-LUMO integrals (40-70 meV). As many of the results are not intuitively obvious, a computational approach provides additional insight into the design of new semiconducting organic materials.
Chavas TEJ, Fuchter MJ, DiMaggio PA, 2018, Unbiased mass spectrometry elucidation of the targets and mechanisms of activity-based probes: A case study involving sulfonyl fluorides, ACS Chemical Biology, Vol: 13, Pages: 2897-2907, ISSN: 1554-8929
The elucidation of protein/drug interactions remains a major challenge in drug discovery. Liquid chromatography–tandem mass spectrometry has emerged as a tremendously powerful technology for this endeavor, but its full potential has yet to be realized owing in part to unresolved challenges in data analysis. Herein, we demonstrate how tandem mass spectrometry can comprehensively map small molecule/peptide adducts when combined with unconstrained sequencing. Using a published sulfonyl fluoride activity-based probe as a model system, this method enabled the discovery of several unreported sites of interaction with its target proteins. Crucially, this probe was found to undergo quantitative displacement and hydrolysis from the target protein’s active site. Isotopic labeling experiments provided a mechanistic rationale for the observed hydrolysis that involves neighboring-group participation. A chemical biology tagging strategy that leverages the probe’s observed lability was developed and shown to be compatible with the original small molecule inhibitor in discovery profiling experiments.
Delves M, Miguel-Blanco C, Matthews H, et al., 2018, A high throughput screen for next-generation leads targeting malaria parasite transmission, Nature Communications, Vol: 9, ISSN: 2041-1723
Spread of parasite resistance to artemisinin threatens current frontline antimalarial therapies, highlighting the need for new drugs with alternative modes of action. Since only 0.2–1% of asexual parasites differentiate into sexual, transmission-competent forms, targeting this natural bottleneck provides a tangible route to interrupt disease transmission and mitigate resistance selection. Here we present a high-throughput screen of gametogenesis against a ~70,000 compound diversity library, identifying seventeen drug-like molecules that target transmission. Hit molecules possess varied activity profiles including male-specific, dual acting male–female and dual-asexual-sexual, with one promising N-((4-hydroxychroman-4-yl)methyl)-sulphonamide scaffold found to have sub-micromolar activity in vitro and in vivo efficacy. Development of leads with modes of action focussed on the sexual stages of malaria parasite development provide a previously unexplored base from which future therapeutics can be developed, capable of preventing parasite transmission through the population.
Fuchter MJ, 2018, Editorial, BIOORGANIC & MEDICINAL CHEMISTRY, Vol: 26, Pages: 2919-2920, ISSN: 0968-0896
Rice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018, A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral helicene molecule (vol 10, pg 1865, 2018), NANOSCALE, Vol: 10, Pages: 9410-9410, ISSN: 2040-3364
Ashley AE, Fuchter MJ, Tighe C, et al., 2018, Direct reductive amination of carbonyl compounds catalyzed by a moisture tolerant Tin (IV) Lewis acid, Advanced Synthesis and Catalysis, Vol: 360, Pages: 1066-1071, ISSN: 1615-4150
Despite the ever-broadening applications of main-group ‘frustrated Lewis pair’ (FLP) chemistry to both new and established reactions, their typical intolerance of water, especially at elevated temperatures (>100 °C), represents a key barrier to their mainstream adoption. Herein we report that FLPs based on the Lewis acid iPr3SnOTf are moisture tolerant in the presence of moderately strong nitrogenous bases, even under high temperature regimes, allowing them to operate as simple and effective catalysts for the reductive amination of organic carbonyls, including for challenging bulky amine and carbonyl substrate partners.
Ali S, Patel H, Periyasamy M, et al., 2018, ICEC0942, an orally bioavailable selective inhibitor of CDK7 for cancer treatment, Molecular Cancer Therapeutics, ISSN: 1535-7163
Recent reports indicate that some cancer types are especially sensitive to transcription inhibition, suggesting that targeting the transcriptional machinery provides new approaches to cancer treatment. Cyclin-dependent kinase (CDK)7 is necessary for transcription, and acts by phosphorylating the C-terminal domain (CTD) of RNA polymerase II (PolII) to enable transcription initiation. CDK7 additionally regulates the activities of a number of transcription factors, including Estrogen receptor-α (ER). Here we describe a new, orally bioavailable CDK7 inhibitor, ICEC0942. It selectively inhibits CDK7, with an IC50 of 40nM; IC50 values for CDK1, CDK2, CDK5 and CDK9 were 45-, 15-, 230- and 30-fold higher. In vitro studies show that a wide range of cancer types are sensitive to CDK7 inhibition with GI50 values ranging between 0.2-0.3 µM. In xenografts of both breast and colorectal cancers, the drug has substantial anti-tumor effects. Additionally, combination therapy with tamoxifen showed complete growth arrest of ER-positive tumor xenografts. Our findings reveal that CDK7 inhibition provides a new approach, especially for ER-positive breast cancer and identify ICEC0942 as a prototype drug with potential utility as a single agent or in combination with hormone therapies for breast cancer. ICEC0942 may also be effective in other cancers that display characteristics of transcription factor addiction, such as acute leukaemia, and small-cell lung cancer.
Lubin AS, Zubiaurre AR, Matthews H, et al., 2018, Development of a photo-crosslinkable diaminoquinazoline inhibitor for target identification in plasmodium falciparum, ACS Infectious Diseases, Vol: 4, Pages: 523-530, ISSN: 2373-8227
Diaminoquinazolines represent a privileged scaffold for antimalarial discovery, including use as putative Plasmodium histone lysine methyltransferase inhibitors. Despite this, robust evidence for their molecular targets is lacking. Here we report the design and development of a small-molecule photo-crosslinkable probe to investigate the targets of our diaminoquinazoline series. We demonstrate the effectiveness of our designed probe for photoaffinity labelling of Plasmodium lysates and identify similarities between the target profiles of the probe and the representative diaminoquinazoline BIX-01294. Initial pull-down proteomics experiments identified 104 proteins from different classes, many of which are essential, highlighting the suitability of the developed probe as a valuable tool for target identification in Plasmodium falciparum.
Hazel P, Kroll SHB, Bondke A, et al., 2018, Corrigendum: Inhibitor selectivity for cyclin-dependent kinase 7: a structural, thermodynamic, and modelling study, ChemMedChem, Vol: 13, Pages: 207-207, ISSN: 1860-7187
Rice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018, A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral helicene molecule, Nanoscale, Vol: 10, Pages: 1865-1876, ISSN: 2040-3364
The potential of a given π-conjugated organic molecule in an organic semiconductor device is highly dependent on molecular packing, as it strongly influences the charge-carrier mobility of the material. Such solid-state packing is sensitive to subtle differences in their intermolecular interactions and is challenging to predict. Chirality of the organic molecule adds an additional element of complexity to intuitive packing prediction. Here we use crystal structure prediction to explore the lattice-energy landscape of a potential chiral organic semiconductor, helicene. We reproduce the experimentally observed enantiopure crystal structure and explain the absence of an experimentally observed racemate structure. By exploring how the hole and electron-mobility varies across the energy–structure–function landscape for helicene, we find that an energetically favourable and frequently occurring packing motif is particularly promising for electron-mobility, with a highest calculated mobility of 2.9 cm2 V−1 s−1 (assuming a reorganization energy of 0.46 eV). We also calculate relatively high hole-mobility in some structures, with a highest calculated mobility of 2.0 cm2 V−1 s−1 found for chains of helicenes packed in a herringbone fashion. Neither the energetically favourable nor high charge-carrier mobility packing motifs are intuitively obvious, and this demonstrates the utility of our approach to computationally explore the energy–structure–function landscape for organic semiconductors. Our work demonstrates a route for the use of computational simulations to aid in the design of new molecules for organic electronics, through the a priori prediction of their likely solid-state form and properties.
Montgomery KS, Davidson RWM, Cao B, et al., 2017, Effective macrophage delivery using RAFT copolymer derived nanoparticles, Polymer Chemistry, Vol: 9, Pages: 131-137, ISSN: 1759-9954
Reversible addition fragmentation chain transfer (RAFT) polymerisation provides a highly controlled means to assemble copolymers of different architectures for a variety of applications, including drug delivery. Polymers consisting of a butyl methacrylate-co-methacrylic acid p(BMA-co-MAA) hydrophobic block and a poly(ethylene glycol) methyl ether methacrylate p(PEGMA-475) hydrophilic block were synthesised via RAFT polymerisation and self-assembled into micelles. A range of micelle particles of different sizes were obtained by varying the composition of the block copolymers. The micelles were crosslinked to form nanoparticles and fluorescently labelled to study cellular internalisation. The prepared nanoparticles were extensively taken up by primary murine macrophages and a promising candidate was identified. To demonstrate effective delivery of a cell impenetrable cargo a fluorescent dye, 4′,6-diamidino-2-phenylindole (DAPI), was encapsulated inside the nanoparticles and successfully delivered to macrophages. The nanoparticles’ stability at increased temperatures and at low concentrations, the tunability of their synthesis and their extensive internalisation by macrophages and performance makes them highly promising delivery vehicles for a range of therapeutics and imaging agents.
Brandt JR, Pospíšil L, Bednárová L, et al., 2017, Intense Redox-Driven Chiroptical Switching with a 580 mV Hysteresis Actuated Through Reversible Dimerization of an Azoniahelicene, Chemical Communications, Vol: 53, Pages: 9059-9062, ISSN: 1364-548X
Electrochemical reduction of an azoniahelicene affords a dimer, accompanied by a strong change in the electronic circular dichroism. The fast dimerisation event leads to a >500 mV shift of the oxidation potential, affording a large area of bistability, where the chiroptical signal only depends on the redox history.
Yang Y, Rice B, Shi X, et al., 2017, Emergent Properties of an Organic Semiconductor Driven by its Molecular Chirality, ACS Nano, Vol: 11, Pages: 8329-8338, ISSN: 1936-0851
Chiral molecules exist as pairs of nonsuperimposable mirror images; a fundamental symmetry property vastly underexplored in organic electronic devices. Here, we show that organic field-effect transistors (OFETs) made from the helically chiral molecule 1-azahelicene can display up to an 80-fold difference in hole mobility, together with differences in thin-film photophysics and morphology, solely depending on whether a single handedness or a 1:1 mixture of left- and right-handed molecules is employed under analogous fabrication conditions. As the molecular properties of either mirror image isomer are identical, these changes must be a result of the different bulk packing induced by chiral composition. Such underlying structures are investigated using crystal structure prediction, a computational methodology rarely applied to molecular materials, and linked to the difference in charge transport. These results illustrate that chirality may be used as a key tuning parameter in future device applications.
Scott DJ, Fuchter MJ, Ashley AE, 2017, Designing effective ‘frustrated Lewis pair’ hydrogenation catalysts, Chemical Society Reviews, Vol: 46, Pages: 5689-5700, ISSN: 1460-4744
The past decade has seen the subject of transition metal-free catalytic hydrogenation develop incredibly rapidly, transforming from a largely hypothetical possibility to a well-established field that can be applied to the reduction of a diverse variety of functional groups under mild conditions. This remarkable change is principally attributable to the development of so-called ‘frustrated Lewis pairs’: unquenched combinations of bulky Lewis acids and bases whose dual reactivity can be exploited for the facile activation of otherwise inert chemical bonds. While a number of comprehensive reviews into frustrated Lewis pair chemistry have been published in recent years, this tutorial review aims to provide a focused guide to the development of efficient FLP hydrogenation catalysts, through identification and consideration of the key factors that govern their effectiveness. Following discussion of these factors, their importance will be illustrated using a case study from our own research, namely the development of FLP protocols for successful hydrogenation of aldehydes and ketones, and for related moisture-tolerant hydrogenation.
Brandt JR, Salerno F, Fuchter MJ, 2017, The added value of small-molecule chirality in technological applications, Nature Reviews Chemistry, Vol: 1, ISSN: 2397-3358
Chirality is a fundamental symmetry property; chiral objects, such as chiral small molecules, exist as a pair of non-superimposable mirror images. Although small-molecule chirality is routinely considered in biologically focused application areas (such as drug discovery and chemical biology), other areas of scientific development have not considered small-molecule chirality to be central to their approach. In this Review, we highlight recent research in which chirality has enabled advancement in technological applications. We showcase examples in which the presence of small-molecule chirality is exploited in ways beyond the simple interaction of two different chiral molecules; this can enable the detection and emission of chiral light, help to control molecular motion, or provide a means to control electron spin and bulk charge transport. Thus, we demonstrate that small-molecule chirality is a highly promising avenue for a wide range of technologically oriented scientific endeavours.
Sundriyal S, Chen P, Lubin A, et al., 2017, Identification of diaminoquinazoline histone lysine methyltransferase structure activity relationships that allow for segregation of human G9a inhibition and anti-Plasmodium activity, MedChemComm, Vol: 8, Pages: 1069-1092, ISSN: 2040-2511
Plasmodium falciparum HKMTs (PfHKMTs) play a key role in controlling Plasmodium gene expression and represent exciting new anti-malarial epigenetic targets. Using an inhibitor series derived from the diaminoquinazoline HKMT inhibitory chemotype, we have previously identified compounds with highly promising antimalarial activity, including irreversible asexual cycle blood stage-independent cytotoxic activity at nM concentrations, oral efficacy in in vivo models of disease, and the unprecedented ability to reactivate dormant liver stage parasites (hypnozoites). However, future development of this series will need to address host versus parasite selectivity, where inhibitory activity against human G9a is removed from the lead compounds, while maintaining potent anti-Plasmodium activity. Herein, we report an extensive study of the SAR of this series against both G9a and P. falciparum. We have identified key SAR features which demonstrate that high parasite vs. G9a selectivity can be achieved by selecting appropriate substituents at position 2, 4 and 7 of the quinazoline ring. We have also, in turn, discovered that potent G9a inhibitors can be identified by employing a 6-carbon ‘Nle mimic’ at position 7. Together, this data suggests that while broadly similar, the G9a and potential PfHKMT target(s) binding pockets and/or binding modes of the diaminoquinazoline analogues exhibit clear and exploitable differences. Based on this, we believe this scaffold to have clear potential for development into a novel anti-malarial therapeutic.
Sundriyal S, Moniot S, Mahmud Z, et al., 2017, Thienopyrimidinone based sirtuin-2 (SIRT2)-selective inhibitors bind in the ligand induced 'selectivity pocket'., Journal of Medicinal Chemistry, Vol: 60, Pages: 1928-1945, ISSN: 0022-2623
Sirtuins (SIRTs) are NAD-dependent deacylases, known to be involved in a variety of pathophysiological processes and thus remain promising therapeutic targets for further validation. Previously, we reported a novel thienopyrimidinone SIRT2 inhibitor with good potency and excellent selectivity for SIRT2. Herein, we report an extensive SAR study of this chemical series and identify the key pharmacophoric elements and physiochemical properties that underpin the excellent activity observed. New analogues have been identified with submicromolar SIRT2 inhibtory activity and good to excellent SIRT2 subtype-selectivity. Importantly, we report a co-crystal structure of one of our compounds (29c) bound to SIRT2. This reveals our series to induce the formation of a previously reported 'selectivity pocket', but to bind in an inverted fashion to what might be intuitively expected. We believe these findings will contribute significantly to understanding of the mechanism of action of SIRT2 inhibitors and to the identification of refined, second generation inhibitors.
Hazel P, Kroll SH, Bondke A, et al., 2017, Inhibitor selectivity for cyclin-dependent kinase 7: a structural, thermodynamic, and modelling study, Chemmedchem, Vol: 12, Pages: 372-380, ISSN: 1860-7187
Deregulation of the cell cycle by mechanisms that lead to elevated activities of cyclin-dependent kinases (CDK) is a feature of many human diseases, cancer in particular. We identified small-molecule inhibitors that selectively inhibit CDK7, the kinase that phosphorylates cell-cycle CDKs to promote their activities. To investigate the selectivity of these inhibitors we used a combination of structural, biophysical, and modelling approaches. We determined the crystal structures of the CDK7-selective compounds ICEC0942 and ICEC0943 bound to CDK2, and used these to build models of inhibitor binding to CDK7. Molecular dynamics (MD) simulations of inhibitors bound to CDK2 and CDK7 generated possible models of inhibitor binding. To experimentally validate these models, we gathered isothermal titration calorimetry (ITC) binding data for recombinant wild-type and binding site mutants of CDK7 and CDK2. We identified specific residues of CDK7, notably Asp155, that are involved in determining inhibitor selectivity. Our MD simulations also show that the flexibility of the G-rich and activation loops of CDK7 is likely an important determinant of inhibitor specificity similar to CDK2.
Calbo J, Weston CE, White A, et al., 2016, Tuning azoheteroarene photoswitch performance through heteroaryl design, Journal of the American Chemical Society, Vol: 139, Pages: 1261-1274, ISSN: 1520-5126
Photoswitchable compounds, which can be reversibly switched between two isomers by light, continue to attract significant attention for a wide array of applications. Azoheteroarenes represent a relatively new but understudied type of photoswitch, where one of the aryl rings from the conventional azobenzene class has been replaced with a five-membered heteroaromatic ring. Initial studies have suggested the azoheteroarenes - the arylazopyrazoles in particular - to have excellent photoswitching properties (quantitative switching and long Z isomer half-life). Here we present a systematic computational and experimental study to elucidate the origin of the long thermal half-lives and excellent addressability of the arylazopyrazoles, and apply this understanding to determine important structure-property relationships for a wide array of comparable azoheteroaryl photoswitches. We identify compounds with Z isomer half-lives ranging from seconds to hours, to days and to years, and variable absorption characteristics; all through tuning of the heteraromatic ring. Conformation perhaps plays the largest role in determining such properties; where the compounds with the longest isomerization half-lives adopt a T-shaped ground state Z isomer conformation and proceed through a T-shaped isomerization pathway, whereas the most complete photoswitching is achieved for compounds that have a twisted (rather than T-shaped) Z-isomer conformation. By balancing these factors, we report a new azopyrazole 3pzH, which can be quantitatively switched to its Z-isomer (>98%) with 355 nm irradiation, near-quantitatively (97%) switched back to the E isomer with 532 nm irradiation, and has a very long half-life for thermal isomerisation (t1/2 = 74 d at 25 °C). Given the large tunability of their properties, the predictive nature of their performance, and the other functional opportunities afforded by usage of a heteroaromatic system, we believe the azoheteroaryl photoswitches to have huge potent
Scott DJ, Phillips NA, Sapsford JS, et al., 2016, Versatile Catalytic Hydrogenation Using A Simple SnIV Lewis Acid, Angewandte Chemie International Edition, Vol: 55, Pages: 14738-14742, ISSN: 1433-7851
Despite the rapid development of frustrated Lewis pair (FLP) chemistry over the last ten years, its application in catalytic hydrogenations remains dependent on a narrow family of structurally similar early main-group Lewis acids (LAs), inevitably placing limitations on reactivity, sensitivity and substrate scope. Herein we describe the FLP-mediated H2 activation and catalytic hydrogenation activity of the alternative LA iPr3SnOTf, which acts as a surrogate for the trialkylstannylium ion iPr3Sn+, and is rapidly and easily prepared from simple, inexpensive starting materials. This highly thermally robust LA is found to be competent in the hydrogenation of a number of different unsaturated functional groups (which is unique to date for main-group FLP LAs not based on boron), and also displays a remarkable tolerance to moisture.
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