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Histone deacetylase 6 (HDAC6) inhibition is an attractive strategy for treating numerous cancers, and HDAC6 catalytic inhibitors are currently in clinical trials. The HDAC6 zinc-finger ubiquitin-binding domain (UBD) binds free C-terminal diglycine motifs of unanchored ubiquitin polymer chains and protein aggregates, playing an important role in autophagy and aggresome assembly. However, targeting this domain with small molecule antagonists remains an underdeveloped avenue of HDAC6-focused drug discovery. We report SGC-UBD253 ( 25 ), a chemical probe potently targeting HDAC6-UBD in vitro with selectivity over nine other UBDs, except for weak USP16 binding. In cells, 25 is an effective antagonist of HDAC6-UBD at 1 μM, with marked proteome-wide selectivity. We identified SGC-UBD253N ( 32 ), a methylated derivative of 25 that is 300-fold less active, serving as a negative control. Together, 25 and 32 could enable further exploration of the biological function of the HDAC6-UBD and investigation of the therapeutic potential of targeting this domain.

The incorporation of the gem-difluoromethylene (CF 2 ) group into organic frameworks is highly sought due to the influence of this unit on the physicochemical and pharmacological properties of molecules. Herein we report an operationally simple, mild, and switchable protocol to access various gem-difluoro compounds that employs chlorodifloroacetic anhydride (CDFAA) as a low-cost and versatile fluoroalkylating reagent. Detailed mechanistic studies revealed that electron-transfer photocatalysis triggers mesolytic cleavage of a C-Cl bond generating a gem-difluoroalkyl radical. In the presence of alkene, this radical species acts as a unique intermediate that, under solvent-controlled reaction conditions, delivers a wide range of gem-difluorinated γ-lactams, γ-lactones, and promotes oxy-perfluoroalkylation. These protocols are flow- and batch-scalable, possess excellent chemo- and regioselectivity, and can be used for the late-stage diversification of complex molecules., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Capitalizing on the late-stage diversification of an essential 1,3-diene intermediate, we describe herein a 9-step enantioselective total synthesis of (+)-hyperforin and (+)-pyrohyperforin, starting from commercially available allylacetone. Our convergent synthesis features a series of critical reactions: 1) an enantioselective deconjugative α-alkylation of α,β-unsaturated acid using chiral lithium amides as noncovalent stereodirecting auxiliaries; 2) a HfCl 4 -mediated carbonyl α-tert-alkylation to forge the intricate bicyclo[3.3.1]nonane framework; 3) an abiotic cascade pyran formation; and 4) a selective 1,4-semihydrogenation of polyenes. During the course of our synthesis, we also identified a 1,2-cyclopropanediol overbred intermediate which was responsible for the 1,3-diene precursor formation through a controlled fragmentation., (© 2022 Wiley-VCH GmbH.)

The dearomatization of 2-naphthols represents a simple method for the construction of complex 3D structures from simple planar starting materials. We describe a cyclopropanation of 2-naphthols that proceeds via cyclopropene ring-opening using rhodium and acid catalysis under mild conditions. The vinyl cyclopropane molecules were formed with high chemoselectivity and scalability, which could be further functionalized at different sites. Both computational and experimental evidence were used to elucidate the reaction mechanism., (© 2021 Wiley-VCH GmbH.)

Herein we report the first enantioselective total synthesis of 3,5-dimethylorsellinic acid-derived meroterpenoids (-)-berkeleyone A and its five congeners ((-)-preaustinoids A, A1, B, B1, and B2) in 12-15 steps, starting from commercially available 2,4,6-trihydroxybenzoic acid hydrate. Based upon the recognition of latent symmetry within D-ring, our convergent synthesis features two critical reactions: 1) a symmetry-breaking, diastereoselective dearomative alkylation to assemble the entire carbon core, and 2) a Sc(OTf) 3 -mediated sequential Krapcho dealkoxycarbonylation/carbonyl α-tert-alkylation to forge the intricate bicyclo[3.3.1]nonane framework. We also conducted our preliminary biomimetic investigations and uncovered a series of rearrangements (α-ketol, α-hydroxyl-β-diketone, etc.) responsible for the biomimetic diversification of (-)-berkeleyone A into its five preaustinoid congeners., (© 2021 Wiley-VCH GmbH.)

USP5 disassembles unanchored polyubiquitin chains to recycle free monoubiquitin, and is one of the 12 ubiquitin specific proteases featuring a zinc finger ubiquitin-binding domain (ZnF-UBD). This distinct structural module has been associated with substrate positioning or allosteric modulation of catalytic activity, but its cellular function remains unclear. We screened a chemical library focused on the ZnF-UBD of USP5, crystallized hits in complex with the protein, and generated a preliminary structure-activity relationship, which enables the development of more potent and selective compounds. This work serves as a framework for the discovery of a chemical probe to delineate the function of USP5 ZnF-UBD in proteasomal degradation and other ubiquitin signaling pathways in health and disease.

The use of ammonium halide salts as metal hydride precursors in a new Pd-catalyzed cycloisomerization of 1,6-diynes, which affords unexplored silylated 2-azafluorenes, is reported. This cascade process includes the addition of a Pd-hydride species to a π-system, intramolecular carbopalladation, and C(sp 2 )-H bond activation. A variety of functional groups are tolerated, and the synthetic utility of the resulting products has been demonstrated by a series of derivatizations.

A simple trifluoromethoxylation method enables non-directed functionalization of C-H bonds on a range of substrates, providing access to aryl trifluoromethyl ethers. This light-driven process is distinctly different from conventional procedures and occurs through an OCF 3 radical mechanism mediated by a photoredox catalyst, which triggers an N-O bond fragmentation. The pyridinium-based trifluoromethoxylation reagent is bench-stable and provides access to synthetic diversity in lead compounds in an operationally simple manner., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

HDAC6 plays a central role in the recruitment of protein aggregates for lysosomal degradation and is a promising target for combination therapy with proteasome inhibitors in multiple myeloma. Pharmacologically displacing ubiquitin from the zinc-finger ubiquitin-binding domain (ZnF-UBD) of HDAC6 is an underexplored alternative to catalytic inhibition. Here, we present the discovery of an HDAC6 ZnF-UBD-focused chemical series and its progression from virtual screening hits to low micromolar inhibitors. A carboxylate mimicking the C-terminal extremity of ubiquitin, and an extended aromatic system stacking with W1182 and R1155, are necessary for activity. One of the compounds induced a conformational remodeling of the binding site where the primary binding pocket opens up onto a ligand-able secondary pocket that may be exploited to increase potency. The preliminary structure-activity relationship accompanied by nine crystal structures should enable further optimization into a chemical probe to investigate the merit of targeting the ZnF-UBD of HDAC6 in multiple myeloma and other diseases.

An enantioconvergent C(sp 3 )-C(sp 3 ) coupling between racemic allenylic electrophiles and alkylzinc reagents has been developed. An Ir/(phosphoramidite,olefin) catalyst provides access to highly enantioenriched allenylic substitution products (93-99% ee) with complete regiocontrol (>50:1 rr in all cases) over the corresponding 1,3-diene isomers which are obtained predominantly when other metal catalysts are emplyed. The synthetic utility of the products obtained was highlighted in a variety of stereoselective transition metal-catalyzed difunctionalization reactions. Furthermore, a combination of experimental and theoretical studies provide support for a putative reaction mechanism wherein enantiodetermining C-C coupling occurs via nucleophilic attack on a highly planarized aryl butadienylium π-system that is coordinated to the Ir center in an η 2 -fashion.

The mechanism of the palladium-catalyzed spirocyclization of acrylamides has been investigated by density functional theory and experimental studies. The results support a mechanistic pathway that proceeds via oxidative addition, intramolecular carbopalladation, C-H bond activation, and migratory insertion sequence. The M06L/def2-TZVPP//BP86/6-31G(d,p)/LANL2DZ level of theory used and the inclusion of solvent effects provide results in good agreement with the experimental data. The C-H bond activation step proceeds via a concerted outer -sphere metallation deprotonation mechanism that explains the absence of a measurable kinetic isotopic effect. The subsequent intermolecular migratory insertion of arynes is significantly faster than the insertion of internal alkynes. Furthermore, the regioselectivities calculated in the case of unsymmetrical reactants are remarkably close to the experimental values. Evaluation of the potential energy surfaces for specific substrates provides an explanation for the lack of product formation observed experimentally. Finally, the computational and experimental analyses of potential side reactions are also presented and support the initially proposed mechanism.

Inhibitors of HDAC6 have attractive potential in numerous cancers. HDAC6 inhibitors to date target the catalytic domains, but targeting the unique zinc-finger ubiquitin-binding domain (Zf-UBD) of HDAC6 may be an attractive alternative strategy. We developed X-ray crystallography and biophysical assays to identify and characterize small molecules capable of binding to the Zf-UBD and competing with ubiquitin binding. Our results revealed two adjacent ligand-able pockets of HDAC6 Zf-UBD and the first functional ligands for this domain.

Herein we describe a rhodium-catalyzed enantioselective isomerization of meso-oxabicyclic alkenes to 1,2-naphthalene oxides. These potentially useful building blocks can be accessed in moderate to excellent yields with impressive enantioselectivities. Additionally, experimental findings supported by preliminary computations suggest that ring-opening reactions of bridgehead disubstituted oxabicyclic alkenes proceed through the intermediacy of these epoxides and may point to a kinetically and thermodynamically favored reductive elimination as the origin for the observed enantioselectivities., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Difficulties associated with handling H 2 and CO in metal-catalyzed processes have led to the development of chemical surrogates to these species. Despite many successful examples using this strategy, the application of convenient hydrogen halide (HX) surrogates in catalysis has lagged behind considerably. We now report the use of ammonium halides as HX surrogates to accomplish a Pd-catalyzed hydrohalogenation of enynes. These safe and practical salts avoid many drawbacks associated with traditional HX sources including toxicity and corrosiveness. Experimental and computational studies support a reaction mechanism involving a crucial E-to-Z vinyl-Pd isomerization and a carbon-halogen bond-forming reductive elimination. Furthermore, rare examples of C(sp 3 )-Br and -Cl reductive elimination from Pd(II) as well as transfer hydroiodination using 1-iodobutane as an alternate HI surrogate are also presented.

A palladium-catalyzed benzylation of α-branched aldehydes has been developed using benzyl methyl carbonates. The method gives access to congested quaternary centers in the vicinity of one of the most sensitive carbonyl functionalities and displays unprecedented generality with respect to both coupling partners. Evidence for the direct involvement of a Pd-η(3)-benzyl intermediate is provided. Extension of this strategy to the γ-benzylation of α,β-unsaturated aldehydes is further demonstrated.

Recent advances in the palladium-catalyzed remote functionalization of carbonyl derivatives are highlighted in this review. The structure of the article is based on the three strategies that have emerged in recent years as the most viable tactics to construct C(sp(3))-C, C(sp(3))-N or C(sp(3))-O bonds at a distance of at least three carbon atoms from the carbonyl functionality. The specific aspects of each of these approaches are discussed in detail (reaction conditions, substrate scope and limitations). As the reading progresses, their complementarity should also appear clearly.

We report the case of a 61-year-old man referred to our department for exertional angina with a history of tri-vessel aneurysmal coronary artery disease. Exercise stress echocardiography was positive for inferior wall hypokinesia. Coronary computed tomography (CT) provided a more accurate characterization of the coronary aneurysms. It detected a laminated thrombus of the proximal left anterior descending and a clover-like aneurysmal dissection of the proximal right coronary artery, which questioned the feasibility of coronary angioplasty. So, the patient was treated with medical therapy only. This case confirmed the importance of coronary CT as diagnostic tool for procedural risk assessment and definition of the most appropriate treatment in patients with coronary aneurysms.

Tetralogy of Fallot is the most common cyanotic congenital heart defect and accounts for about 5% of all congenital cardiopathies. The definitive treatment modality for tetralogy of Fallot is reparative surgery, which is recommended to be performed by the time of diagnosis. Without surgical repair, most patients would die during their childhood. In the past, survival data indicated that 66% of persons with tetralogy of Fallot not surgically treated lived until the age of 1, 49% lived until the age of 3, and 24% lived until the age of 10. We now present a rare case of a man with unrepaired tetralogy of Fallot who survived until the age of 85. He presented to our emergency room for dyspnea and palpitations due to a new-onset high-frequency atrial fibrillation and acute heart failure; transthoracic echocardiography showed the presence of tetralogy of Fallot. By consulting the scientific literature, we can say that this is the second patient who survived more than 80 years without surgical intervention., (© 2012 Wiley Periodicals, Inc.)

We report a case of a 66-year-old Caucasian male who presented to our department with unstable angina in July 2011. He had a medical history of trivessel coronary artery disease and underwent several percutaneous coronary interventions (2003, 2004, and 2006). The latest coronary angiography, performed in January 2011, showed mild intimal hyperplasia within the proximal left anterior descending segment, treated with a sirolimus-eluting stent in 2003. On admission, electrocardiogram was positive for a recent acute coronary syndrome, so the patient underwent coronary angiography, which showed proximal left anterior descending stent thrombosis, occurred eight years after drug-eluting stent implantation. Intravascular ultrasound revealed a soft plaque rupture within the stented segment, which was the cause of stent thrombosis. So the lack of endothelialization over stent struts is not the only mechanism determining acute coronary syndromes late after stent implantation. In-stent neoatherosclerosis, frequently disregarded, is another possible actor especially of very late thrombotic events. However, the pathogenesis of this phenomenon has not been clearly established.