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JAK1, JAK2, JAK3, and TYK2 belong to the JAK (Janus kinase) family. They play critical roles in cytokine signaling. Constitutive activation of JAK/STAT pathways is associated with a wide variety of...

Covalent PROTACs combine the cutting edge research areas of targeted covalent inhibitors (TCIs) and proteolysis targeting chimeras (PROTACs). This nascent field of research has already demonstrated several interesting findings, and holds an immense amount of potential to expand the druggable proteome. In this opinion, we present some of these intriguing early findings and discuss the potential advantages and disadvantages of this approach.

JAK1, JAK2, JAK3, and TYK2 belong to the JAK (Janus kinase) family. They play critical roles in cytokine signaling. Constitutive activation of JAK/STAT pathways is associated with a wide variety of diseases. Particularly, pSTAT3 is observed in response to the treatment with inhibitors of oncogenic signaling pathways such as EGFR, MAPK, and AKT and is associated with resistance or poorer response to agents targeting these pathways. Among the JAK family kinases, JAK1 has been shown to be the primary driver of STAT3 phosphorylation and signaling; therefore, selective JAK1 inhibition can be a viable means to overcome such treatment resistances. Herein, an account of the medicinal chemistry optimization from the promiscuous kinase screening hit

Over the past decade targeted covalent inhibitors have undergone a renaissance due to the clinical validation and regulatory approval of several small molecule therapeutics that are designed to irreversibly modify their target protein. Invariably, these compounds rely on the serendipitous placement of a cysteine residue proximal to the small molecule binding site; while this strategy has afforded numerous successes, it necessarily limits the number of proteins that can be targeted by this approach. This drawback has led several research groups to develop novel methodologies that target non-cysteine residues for covalent modification. Herein, we survey the current literature of warheads that covalently modify non-cysteine amino acids in proteins.

Janus kinases (JAKs) have been demonstrated to be critical in cytokine signaling and have thus been implicated in both cancer and inflammatory diseases. The JAK family consists of four highly homologous members: JAK1-3 and TYK2. The development of small-molecule inhibitors that are selective for a specific family member would represent highly desirable tools for deconvoluting the intricacies of JAK family biology. Herein, we report the discovery of a potent JAK1 inhibitor, 24, which displays ∼1000-fold selectivity over the other highly homologous JAK family members (determined by biochemical assays), while also possessing good selectivity over other kinases (determined by panel screening). Moreover, this compound was demonstrated to be orally bioavailable and possesses acceptable pharmacokinetic parameters. In an in vivo study, the compound was observed to dose dependently modulate the phosphorylation of STAT3 (a downstream marker of JAK1 inhibition).

Sulfonyl fluorides (SFs) have recently emerged as a promising warhead for the targeted covalent modification of proteins. Despite numerous examples of the successful deployment of SFs as covalent probe compounds, a detailed exploration of the factors influencing the stability and reactivity of SFs has not yet appeared. In this work we present an extensive study on the influence of steric and electronic factors on the reactivity and stability of the SF and related SVI-F groups. While SFs react rapidly with N-acetylcysteine, the resulting adducts were found to be unstable, rendering SFs inappropriate for the durable covalent inhibition of cysteine residues. In contrast, SFs afforded stable adducts with both N-acetyltyrosine and N-acetyllysine; furthermore, we show that the reactivity of arylsulfonyl fluorides towards these nucleophilic amino acids can be predictably modulated by adjusting the electronic properties of the warhead. These trends were largely conserved when the covalent reaction occurred within a protein binding pocket. We have also obtained a crystal structure depicting covalent modification of the catalytic lysine of a tyrosine kinase (FGFR1) by the ATP analog 5'-O-3-((fluorosulfonyl)benzoyl)adenosine (m-FSBA). Highly reactive warheads were demonstrated to be unstable with respect to hydrolysis in buffered aqueous solutions, indicating that warhead reactivity must be carefully tuned to provide optimal rates of protein modification. Our results demonstrate that the reactivity of SFs complements that of more commonly studied acrylamides, and we hope that this work spurs the rational design of novel SF-containing covalent probe compounds and inhibitors, particularly in cases where a suitably positioned cysteine residue is not present.

Janus kinases (JAKs) are a family of four enzymes; JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2) that are critical in cytokine signalling and are strongly linked to both cancer and inflammatory diseases. There are currently two launched JAK inhibitors for the treatment of human conditions: tofacitinib for Rheumatoid arthritis (RA) and ruxolitinib for myeloproliferative neoplasms including intermediate or high risk myelofibrosis and polycythemia vera. Areas covered: This review covers patents claiming activity against one or more JAK family members in the period 2013-2015 inclusive, and covers 95 patents from 42 applicants, split over two parts. The authors have ordered recent patents according to the primary applicant's name, with part 1 covering A through to I. Expert opinion: Inhibition of JAK-family kinases is an area of growing interest, catalysed by the maturity of data on marketed inhibitors ruxolitinib and tofacitinib in late stage clinical trials. Many applicants are pursuing traditional fast-follower strategies around these inhibitors, with a range of chemical strategies adopted. The challenge will be to show sufficient differentiation to the originator compounds, since dose limiting toxicities with such agents appear to be on target and mechanism-related and also considering that such agents may be available as generic compounds by the time follower agents reach market.

Spleen tyrosine kinase (SYK) is a non-receptor cytosolic kinase. Due to its pivotal role in B cell receptor and Fc-receptor signaling, inhibition of SYK has been targeted in a variety of disease areas. Herein, we report the optimization of a series of potent and selective SYK inhibitors, focusing on improving metabolic stability, pharmacokinetics and hERG inhibition. As a result, we identified 30, which exhibited no hERG activity but unfortunately was poorly absorbed in rats and mice. We also identified a SYK chemical probe, 17, which exhibits excellent potency at SYK, and an adequate rodent PK profile to support in vivo efficacy/PD studies.

Introduction: Loss of immune surveillance is required for cancer cell growth and metastasis; tumors co-opt suppressive mechanisms to evade detection by the immune system. The immune system is equipped with multiple feedback mechanisms to limit inflammation to prevent autoimmunity; tumors activate these pathways to escape immunity. HPK1 (hematopoietic progenitor kinase 1) is a negative regulator of T-cell activation; the kinase activity limits T-cell signaling and tumoricidal cytokine production. Recent literature has shown that inactivation of the kinase function of HPK1 prevents tumor progression in murine tumor models (1). Experimental Procedures: We used lentiviral delivered shRNAs and CRISPR/Cas9 technology to delete HPK1 in Jurkat cells and primary human T cells, respectively. Jurkat T cells (wt/KO) were activated with anti-CD3 antibody and cell lysates were assessed by Western blot to examine signaling events downstream of the T-cell receptor (TCR). Primary human T cells or CRISPR/Cas9 KO T cells were activated in vitro using anti-CD3/anti-CD28 antibodies in the presence or absence of prostaglandin E2 (PGE2). Cytokines were quantified by ELISA. Results: We present novel findings demonstrating that the role of HPK1 is conserved in human Jurkat cells as well as in primary human T cells. Loss of HPK1 enhanced T-cell receptor signaling in Jurkat cells. In CRISPR/Cas9 KO HPK1 primary human T cells, TCR activation resulted in enhanced cytokine secretion and proliferation concomitant to a decrease in pSLP76, the target molecule phosphorylated by HPK1. In addition, HPK1 KO cells were rescued from PGE2-mediated suppression. A screening and assessment of HPK-1 inhibitor compounds that enhance T-cell function is ongoing. Conclusions: In summary, HPK1 function is conserved in human T cells and inhibitors of HPK1 could enhance antitumor immunity through increased T-cell function, overcoming suppressive signals in the tumor microenvironment and broadening the response to check point inhibitors for cancer immunotherapy. Reference 1. Hernandez S, Qing J et al. The kinase activity of hematopoietic progenitor kinase 1 is essential for the regulation of T cell function. Cell Rep 2018;25:80-94. Citation Format: Neil Grimster, Lisa Drew, Stephen Fawell, Deanna A Mele, Gayathri Bommakanti, Minhui Shen, Kevin Xu, Kun Song, Rob Ziegler, Jason Kettle, Adelphe Mfuh, Jason Sheilds. Releasing the brake on T-cell activation through inhibition of HPK1 [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A56.

Protein aggregation is a hallmark of several neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases. It has been shown that lysine residues play a key role in the formation of these aggregates. Thus, the ability to disrupt aggregate formation by covalently modifying lysine residues could lead to the discovery of therapeutically relevant antiamyloidogenesis compounds. Herein, we demonstrate that an ortho-iminoquinone (IQ) can be utilized to inhibit amyloid aggregation. Using alpha-synuclein and Aβ1–40 as model amyloidogenic proteins, we observed that IQ was able to react with lysine residues and reduce amyloid aggregation. We also observed that IQ reacted with free amines within the amyloid fibrils preventing their dissociation and seeding capacity.

Over the last ten years, targeted covalent inhibition has become a key discipline within medicinal chemistry research, most notably in the development of oncology therapeutics. One area where this approach is underrepresented, however, is in targeting protein-protein interactions. This is primarily because these hydrophobic interfaces lack appropriately located cysteine residues to allow for standard conjugate addition chemistry. Herein, we report our development of the first covalent inhibitors of the antiapoptotic protein B-cell lymphoma extra-large (Bcl-xL), utilizing a sulfonyl fluoride (SF) warhead to selectively covalently modify tyrosine 101 of the BH3 domain-binding groove. These compounds display time-dependent inhibition in a biochemical assay and are cellularly active (U266B1). In addition, compound 7 was further elaborated to generate a chemical-biology probe molecule, which may find utility in understanding the intricacies of Bcl-xL biology.

We seek fluorogenic small molecules that generate a fluorescent conjugate signal if and only if they react with a given protein-of-interest (i.e., small molecules for which noncovalent binding to the protein-of-interest is insufficient to generate fluorescence). Consequently, it is the new chemical entity afforded by the generally irreversible reaction between the small molecule and the protein-of-interest that enables the energy of an electron occupying the lowest unoccupied molecular orbital (LUMO) of the chromophore to be given off as a photon instead of being dissipated by nonradiative mechanisms in complex biological environments. This category of fluorogenic small molecules is created by starting with environmentally sensitive fluorophores that are modified by an essential functional group that efficiently quenches the fluorescence until a chemoselective reaction between that functional group and the protein-of-interest occurs, yielding the fluorescent conjugate. Fluorogenic small molecules are envisioned to be useful for a wide variety of applications, including live cell imaging without the requirement for washing steps and pulse-chase kinetic analyses of protein synthesis, trafficking, degradation, etc. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 484–495, 2014.

A convenient one-pot asymmetric synthesis of 2,3-dihydropyrroles from in situ generated triflated triazoles and olefins is described that further expands the utility of azavinyl carbene chemistry and provides access to an important class of cyclic enamides. Mechanistic investigations support the involvement of triflated cyclopropylaldimine intermediates in the formation of 2,3-dihydropyrrole. To the best of our knowledge, this is the first example of a chiral Brønsted acid catalyzed rearrangement of cyclopropylimines into enantioenriched 2,3-dihydropyrroles.

Molecules that bind selectively to a given protein and then undergo a rapid chemoselective reaction to form a covalent conjugate have utility in drug development. Herein a library of 1,3,4-oxadiazoles substituted at the 2 position with an aryl sulfonyl fluoride and at the 5 position with a substituted aryl known to have high affinity for the inner thyroxine binding subsite of transthyretin (TTR) were conceived of by structure-based design principles and were chemically synthesized. When bound in the thyroxine binding site, most of the aryl sulfonyl fluorides react rapidly and chemoselectively with the pKa-perturbed K15 residue, kinetically stabilizing TTR and thus preventing amyloid fibril formation, known to cause polyneuropathy. Conjugation t50s range from 1 to 4 min, ~ 1400 times faster than the hydrolysis reaction outside the thyroxine binding site. X-ray crystallography confirms the anticipated binding orientation and sheds light on the sulfonyl fluoride activation leading to the sulfonamide linkage to TTR. A few of the aryl sulfonyl fluorides efficiently form conjugates with TTR in plasma. A few of the TTR covalent kinetic stabilizers synthesized exhibit fluorescence upon conjugation and therefore could have imaging applications as a consequence of the environment sensitive fluorescence of the chromophore.

The acetylcholine-binding proteins (AChBPs), which serve as structural surrogates for the extracellular domain of nicotinic acetylcholine receptors (nAChRs), were used as reaction templates for in situ click-chemistry reactions to generate a congeneric series of triazoles from azide and alkyne building blocks. The catalysis of in situ azide-alkyne cycloaddition reactions at a dynamic subunit interface facilitated the synthesis of potentially selective compounds for nAChRs. We investigated compound sets generated in situ with soluble AChBP templates through pharmacological characterization with α7 and α4β2 nAChRs and 5-hydroxytryptamine type 3A receptors. Analysis of activity differences between the triazole 1,5-syn- and 1,4-anti-isomers showed a preference for the 1,4-anti-triazole regioisomers among nAChRs. To improve nAChR subtype selectivity, the highest-potency building block for α7 nAChRs, i.e., 3α-azido-N-methylammonium tropane, was used for additional in situ reactions with a mutated Aplysia californica AChBP that was made to resemble the ligand-binding domain of the α7 nAChR. Fourteen of 50 possible triazole products were identified, and their corresponding tertiary analogs were synthesized. Pharmacological assays revealed that the mutated binding protein template provided enhanced selectivity of ligands through in situ reactions. Discrete trends in pharmacological profiles were evident, with most compounds emerging as α7 nAChR agonists and α4β2 nAChR antagonists. Triazoles bearing quaternary tropanes and aromatic groups were most potent for α7 nAChRs. Pharmacological characterization of the in situ reaction products established that click-chemistry synthesis with surrogate receptor templates offered novel extensions of fragment-based drug design that were applicable to multisubunit ion channels.

Nicotinic acetylcholine receptors (nAChRs), which are responsible for mediating key physiological functions, are ubiquitous in the central and peripheral nervous systems. As members of the Cys loop ligand-gated ion channel family, neuronal nAChRs are pentameric, composed of various permutations of α (α2 to α10) and β (β2 to β4) subunits forming functional heteromeric or homomeric receptors. Diversity in nAChR subunit composition complicates the development of selective ligands for specific subtypes, since the five binding sites reside at the subunit interfaces. The acetylcholine binding protein (AChBP), a soluble extracellular domain homologue secreted by mollusks, serves as a general structural surrogate for the nAChRs. In this work, homomeric AChBPs from Lymnaea and Aplysia snails were used as in situ templates for the generation of novel and potent ligands that selectively bind to these proteins. The cycloaddition reaction between building-block azides and alkynes to form stable 1,2,3-triazoles was used to generate the leads. The extent of triazole formation on the AChBP template correlated with the affinity of the triazole product for the nicotinic ligand binding site. Instead of the in situ protein-templated azide-alkyne cycloaddition reaction occurring at a localized, sequestered enzyme active center as previously shown, we demonstrate that the in situ reaction can take place at the subunit interfaces of an oligomeric protein and can thus be used as a tool for identifying novel candidate nAChR ligands. The crystal structure of one of the in situ-formed triazole-AChBP complexes shows binding poses and molecular determinants of interactions predicted from structures of known agonists and antagonists. Hence, the click chemistry approach with an in situ template of a receptor provides a novel synthetic avenue for generating candidate agonists and antagonists for ligand-gated ion channels.

A new tandem catalysis strategy that transforms alkyne derivatives to (E)-enol-equivalents followed by stereoselective anti-selective aldol coupling or syn-selective [3,3]-rearrangement transformations is reported. The mechanism is thought to proceed through an interchanging series of Lewis acid and Bronsted acid catalyzed reactions via the intermediacy of a ketiminum ion species.

Targeted covalent inhibition of disease-associated proteins has become a powerful methodology in the field of drug discovery, leading to the approval of new therapeutics. Nevertheless, current approaches are often limited owing to their reliance on a cysteine residue to generate the covalent linkage. Here we used aryl boronic acid carbonyl warheads to covalently target a noncatalytic lysine side chain, and generated to our knowledge the first reversible covalent inhibitors for Mcl-1, a protein-protein interaction (PPI) target that has proven difficult to inhibit via traditional medicinal chemistry strategies. These covalent binders exhibited improved potency in comparison to noncovalent congeners, as demonstrated in biochemical and cell-based assays. We identified Lys234 as the residue involved in covalent modification, via point mutation. The covalent binders discovered in this study will serve as useful starting points for the development of Mcl-1 therapeutics and probes to interrogate Mcl-1-dependent biological phenomena.

Janus kinases are a family of four enzymes; JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2) that are critical in cytokine signalling, with constitutive activation of JAK/STAT pathways associated with a wide variety of malignancies. Elevated JAK/STAT signalling leading to increased activation of STAT3 is reported in a wide variety of cancers, including breast, liver, prostate, colorectal, head and neck, oesophageal, pancreatic, bladder, and non-small cell lung, and is implicated in the pathogenesis of diffuse large B-cell lymphoma and nasopharyngeal carcinomas. Overall, up to 70% of human tumours are linked to persistent elevated STAT3 activity which can be associated with poorer prognosis in many of these settings. In addition, elevated pSTAT3 is observed in response to chemotherapy treatment, and also in response to treatment with inhibitors of oncogenic signalling pathways such as EGFR, MAPK and AKT, and is associated with resistance or poorer response to agents targeting these pathways. In many of these cases, JAK1 is believed to be a primary driver of STAT3 phosphorylation and signalling, suggesting inhibition of JAKs as a therapeutic approach to treat these potential resistance mechanisms. The mixed JAK1/2 kinase inhibitor ruxolitinib is approved for the treatment of myeloproliferative neoplasms including intermediate or high risk myelofibrosis and polycythemia vera and has been tested in a variety of tumor settings. Since JAK2 is essential for the signal transduction downstream of erythropoietin, thrombopoietin and related receptors that control erythrocyte and megakaryocyte expansion, dosing of inhibitors that target JAK2 can be limited by toxicities such as thrombocytopenia and anaemia. Starting from a non-kinome selective screening hit, structure-based design was used to optimise a series of aminopyrimidines that led to JAK1-selective candidate drug AZD4205. This compound demonstrates ATP competitive binding with IC50’s in a high ATP concentration enzyme assay against JAK1 of 73 nM (Ki = 2.8 nM), with high selectivity against JAK2 and JAK3 with IC50’s of 13,233 nM and >30,000 nM respectively. In addition it showed potent inhibition of p-STAT3 in a cell based assay of JAK1 activity with an IC50 of 128 nM and excellent selectivity across the kinome. In summary, AZD4205 is a highly potent JAK1-selective kinase inhibitor with excellent preclinical pharmacokinetics with potential for further clinical development. The optimization from screening hit to first disclosure of this candidate drug will be presented. Citation Format: Jason G. Kettle, Qibin Su, Neil Grimster, Sameer Kawatkar, Scott Throner, Richard Woessner, Huawei Chen, Geraldine Bebernitz, Kristen Bell, Erica Anderson, Linette Ruston, Jon Winter-Holt, Paul Lyne, Melissa Vasbinder, Claudio Chuaqui. Discovery of the JAK1 selective kinase inhibitor AZD4205 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 979. doi:10.1158/1538-7445.AM2017-979

A convenient one-pot asymmetric synthesis of 2,3-dihydropyrroles from in situ generated triflated triazoles and olefins is described that further expands the utility of azavinyl carbene chemistry and provides access to an important class of cyclic enamides. Mechanistic investigations support the involvement of triflated cyclopropylaldimine intermediates in the formation of 2,3-dihydropyrrole. To the best of our knowledge, this is the first example of a chiral Bronsted acid catalyzed rearrangement of cyclopropylimines into enantioenriched 2,3-dihydropyrroles.

We seek fluorogenic small molecules that generate a fluorescent conjugate signal if and only if they react with a given protein-of-interest (i.e., small molecules for which non-covalent binding to the protein-of-interest is insufficient to generate fluorescence). Consequently, it is the new chemical entity afforded by the generally irreversible reaction between the small molecule and the protein-of-interest that enables the energy of an electron occupying the lowest unoccupied molecular orbital (LUMO) of the chromophore to be given off as a photon instead of being dissipated by non-radiative mechanisms in complex biological environments. This category of fluorogenic small molecules is created by starting with environmentally sensitive fluorophores that are modified by an essential functional group that efficiently quenches the fluorescence until a chemoselective reaction between that functional group and the protein-of-interest occurs, yielding the fluorescent conjugate. Fluorogenic small molecules are envisioned to be useful for a wide variety of applications, including live cell imaging without the requirement for washing steps and pulse-chase kinetic analyses of protein synthesis, trafficking, degradation, etc.

Protein misfolding and/or aggregation has been implicated as the cause of several human diseases, such as Alzheimer's and Parkinson's diseases and familial amyloid polyneuropathy. These maladies are referred to as amyloid diseases, named after the cross-β-sheet amyloid fibril aggregates or deposits common to these disorders. Epigallocatechin-3-gallate (EGCG), the principal polyphenol present in green tea, has been shown to be effective at preventing aggregation and is able to remodel amyloid fibrils comprising different amyloidogenic proteins, although the mechanistic underpinnings are unclear. Herein, we work toward an understanding of the molecular mechanism(s) by which EGCG remodels mature amyloid fibrils made up of Aβ(1-40), IAPP(8-24), or Sup35NM(7-16). We show that EGCG amyloid remodeling activity in vitro is dependent on auto-oxidation of the EGCG. Oxidized and unoxidized EGCG binds to amyloid fibrils, preventing the binding of thioflavin T. This engagement of the hydrophobic binding sites in Aβ(1-40), IAPP(8-24), or Sup35NM(Ac7-16) Y→F amyloid fibrils seems to be sufficient to explain the majority of the amyloid remodeling observed by EGCG treatment, although how EGCG oxidation drives remodeling remains unclear. Oxidized EGCG molecules react with free amines within the amyloid fibril through the formation of Schiff bases, cross-linking the fibrils, which may prevent dissociation and toxicity, but these aberrant post-translational modifications do not appear to be the major driving force for amyloid remodeling by EGCG treatment. These insights into the molecular mechanism of action of EGCG provide boundary conditions for exploring amyloid remodeling in more detail.

Pharmacologic chaperoning is a therapeutic strategy being developed to improve the cellular folding and trafficking defects associated with Gaucher disease, a lysosomal storage disorder caused by point mutations in the gene encoding acid-β-glucosidase (GCase). In this approach, small molecules bind to and stabilize mutant folded or nearly folded GCase in the endoplasmic reticulum (ER), increasing the concentration of folded, functional GCase trafficked to the lysosome where the mutant enzyme can hydrolyze the accumulated substrate. To date, the pharmacologic chaperone (PC) candidates that have been investigated largely have been active site-directed inhibitors of GCase, usually containing five- or six-membered rings, such as modified azasugars. Here we show that a seven-membered, nitrogen-containing heterocycle (3,4,5,6-tetrahydroxyazepane) scaffold is also promising for generating PCs for GCase. Crystal structures reveal that the core azepane stabilizes GCase in a variation of its proposed active conformation, whereas binding of an analogue with an N-linked hydroxyethyl tail stabilizes GCase in a conformation in which the active site is covered, also utilizing a loop conformation not seen previously. Although both compounds preferentially stabilize GCase to thermal denaturation at pH 7.4, reflective of the pH in the ER, only the core azepane, which is a mid-micromolar competitive inhibitor, elicits a modest increase in enzyme activity for the neuronopathic G202R and the non-neuronopathic N370S mutant GCase in an intact cell assay. Our results emphasize the importance of the conformational variability of the GCase active site in the design of competitive inhibitors as PCs for Gaucher disease.

A new tandem catalysis strategy is developed, that transforms alkyne derivatives into (E)-enol equivalents.

Highly reactive rhodium(II) N-trifluoromethylsulfonyl azavinyl carbenes are formed in situ from NH-1,2,3-triazoles, triflic anhydride, and rhodium carboxylates. They rapidly and selectively react with olefins, providing cyclopropane carboxaldehydes and 2,3-dihydropyrroles in generally excellent yields and high enantio- and diastereoselectivity.

We have developed a new site-selective Cu(II)-catalyzed C−H bond functionalization process that can selectively arylate indoles at either the C3 or C2 position under mild conditions. The scope of the arylation process is broad and tolerates broad functionality on both the indole and aryl unit, which makes it amenable to further elaboration. The mechanism of the arylation reaction is proposed to proceed via a Cu(III)−aryl species that undergoes initial electrophilic addition at the C3 position of the indole motif. We speculate that site of indole arylation arises through a migration of the Cu(III)−aryl group from C3 to C2, and this can be controlled by the nature of the group on the nitrogen atom; free (NH)- and N-alkylindoles deliver the C3-arylated product, whereas N-acetylindoles afford the C2 isomer, both with excellent yield and selectivity.

Myeloid cell leukemia 1 (Mcl-1), a potent anti-apoptotic protein of the BCL2 family, has been studied as a key resistance factor in human cancers. Restoring apoptotic signals by inactivating Mcl-1 protein interactions with small molecule inhibitors has been intensively pursued as targets for cancer therapeutics. We herein describe our effort towards the structure-based design, synthesis and evaluation of first potent, covalent binders of Mcl-1. The resulting inhibitors specifically modified a non-catalytic lysine residue with high level of Mcl-1 potency in biochemical and cell based assays. Our covalent inhibitors could provide potent probes to interrogate Mcl-1 dependent cancer biology. Citation Format: Qibin Su, Gizem Akçay, Neil Grimster, Matthew Belmonte, Philip Rawlins, Michelle Lamb, Alexander Hird, Brian Aquila. Inhibition of Mcl-1 through covalent modification of a non-catalytic lysine side chain. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C40.

A palladium catalyzed C−H bond functionalization system that operates under ambient and aerobic conditions can be used to alkenylate pyrroles with control of regioselectivty. A steric and electronic control strategy can be used to influence positional control in the C−H bond functionalization process that results in either the C2 or C3 alkenylated products. Air, molecular oxygen, or tBuOOBz can be used as reoxidant in this mild process, and the reaction works on a range of substrates. Finally a catalytic aerobic annulation strategy is described that can be controlled to produce cyclization at either the C2 or C3 positions, thus forming diverse pyrrole products.

Highly reactive rhodium(II) N-trifluoromethylsulfonyl azavinyl carbenes are formed in situ from NH-1,2,3-triazoles, triflic anhydride, and rhodium carboxylates. They rapidly and selectively react with olefins, providing cyclopropane carboxaldehydes and 2,3-dihydropyrroles in generally excellent yields and high enantio- and diastereoselectivity.