Hydrogen-bond-acceptor ligands enable distal C(sp3)-H arylation of free alcohols.

The functionalization of C-H bonds in organic molecules is one of the most direct approaches for chemical synthesis. Recent advances in catalysis have allowed native chemical groups such as carboxylic acids, ketones and amines to control and direct C(sp3)-H activation1-4. However, alcohols, among the most common functionalities in organic chemistry5, have remained intractable because of their low affinity for late transition-metal catalysts6,7. Here we describe ligands that enable alcohol-directed arylation of δ-C(sp3)-H bonds. We use charge balance and a secondary-coordination-sphere hydrogen-bonding interaction-evidenced by structure-activity relationship studies, computational modelling and crystallographic data-to stabilize L-type hydroxyl coordination to palladium, thereby facilitating the assembly of the key C-H cleavage transition state. In contrast to previous studies in C-H activation, in which secondary interactions were used to control selectivity in the context of established reactivity8-13, this report demonstrates the feasibility of using secondary interactions to enable challenging, previously unknown reactivity by enhancing substrate-catalyst affinity.

Formal γ-C-H Functionalization of Cyclobutyl Ketones: Synthesis of cis-1,3-Difunctionalized Cyclobutanes.

1,3-Difunctionalized cyclobutanes are an emerging scaffold in medicinal chemistry that can confer beneficial pharmacological properties to small-molecule drug candidates. However, the diastereocontrolled synthesis of these compounds typically requires complicated synthetic routes, indicating a need for novel methods. Here, we report a sequential C-H/C-C functionalization strategy for the stereospecific synthesis of cis-γ-functionalized cyclobutyl ketones from readily available cyclobutyl aryl ketones. Specifically, a bicyclo[1.1.1]pentan-2-ol intermediate is generated from the parent cyclobutyl ketone via an optimized Norrish-Yang procedure. This intermediate then undergoes a ligand-enabled, palladium-catalyzed C-C cleavage/functionalization to produce valuable cis-γ-(hetero)arylated, alkenylated, and alkynylated cyclobutyl aryl ketones, the benzoyl moiety of which can subsequently be converted to a wide range of functional groups including amides and esters.

Ligand-Enabled C-H Hydroxylation with Aqueous H2O2 at Room Temperature.

With the large number of Pd(II)-catalyzed C-H activation reactions of native substrates developed in the past decade, the development of catalysts to enable the use of green oxidants under safe and practical conditions has become an increasingly important challenge. Notably, the compatibility of Pd(II) catalysts with sustainable aqueous H2O2 has been a long-standing challenge in catalysis including Wacker-type oxidations. We report herein a bifunctional bidentate carboxyl-pyridone (CarboxPyridone) ligand that enables room-temperature Pd-catalyzed C-H hydroxylation of a broad range of benzoic and phenylacetic acids with an industry-compatible oxidant, aqueous hydrogen peroxide (35% H2O2). The scalability of this methodology is demonstrated by a 1000 mmol scale reaction of ibuprofen (206 g) using only a 1 mol % Pd catalyst loading. The utility of this protocol is further illustrated through derivatization of the products and synthesis of polyfluorinated natural product coumestan and pterocarpene from phenol intermediates prepared using this methodology.

Molecular editing of aza-arene C-H bonds by distance, geometry and chirality.

Direct molecular editing of heteroarene carbon-hydrogen (C-H) bonds through consecutive selective C-H functionalization has the potential to grant rapid access into diverse chemical spaces, which is a valuable but often challenging venture to achieve in medicinal chemistry1. In contrast to electronically biased heterocyclic C-H bonds2-9, remote benzocyclic C-H bonds on bicyclic aza-arenes are especially difficult to differentiate because of the lack of intrinsic steric/electronic biases10-12. Here we report two conceptually distinct directing templates that enable the modular differentiation and functionalization of adjacent remote (C6 versus C7) and positionally similar (C3 versus C7) positions on bicyclic aza-arenes through careful modulation of distance, geometry and previously unconsidered chirality in template design. This strategy enables direct C-H olefination, alkynylation and allylation at adjacent C6 and C7 positions of quinolines in the presence of a competing C3 position that is spatially similar to C7. Notably, such site-selective, iterative and late-stage C-H editing of quinoline-containing pharmacophores can be performed in a modular fashion in different orders to suit bespoke synthetic applications. This Article, in combination with previously reported complementary methods, now fully establishes a unified late-stage 'molecular editing' strategy to directly modify bicyclic aza-arenes at any given site in different orders.

Empirical Guidelines for the Development of Remote Directing Templates through Quantitative and Experimental Analyses.

The ability to differentiate and selectively activate remote C-H bonds represents a perennial challenge in the field of C-H activation. Since its first report in 2012, a now-established "directing template" (DT) approach remains demonstrably effective for the functionalization of remote C-H bonds. As selectivity is hypothesized to be principally determined by the optimal positioning of the reactive catalyst to a target C-H bond, a DT's spatial factors are particularly important toward achieving high selectivity, though a systematic study on its requisite factors remain unelucidated. Through an in-depth analysis of 119 structurally unique published remote DTs, this report summarizes the key factors that are central toward achieving high selectivity at defined aryl positions, which are experimentally corroborated through the development of new aliphatic meta and para-selective DTs for electronically unbiased arenes. These empirical rules, which summarize key distance and geometric factors, are expected to be useful tools for the future development of site-selective arene C-H activation as well as other reactions that rely on covalent/noncovalent DT-mediated remote regioselection.

Clinical impact of serum exosomal microRNA in liver fibrosis.

BACKGROUND/AIM: We investigated alterations in the expression of serum exosomal miRNAs with the progression of liver fibrosis and evaluated their clinical applicability as biomarkers. METHODS: This study prospectively enrolled 71 patients who underwent liver biopsy at an academic hospital in Korea. Exosomes were extracted from serum samples, followed by next-generation sequencing (NGS) of miRNAs and targeted real-time quantitative polymerase chain reaction. A model was derived to discriminate advanced fibrosis based on miRNA levels and the performance of this model was evaluated. Validation of the effect of miRNA on liver fibrosis in vitro was followed. RESULTS: NGS data revealed that exosomal miR-660-5p, miR-125a-5p, and miR-122 expression were changed significantly with the progression of liver fibrosis, of which miR-122 exhibited high read counts enough to be used as a biomarker. The level of exosomal miR-122 decreased as the pathologic fibrosis grade progressed and patients with biopsy-proven advanced fibrosis had significantly lower levels of exosomal miR-122 (P < 0.001) than those without advanced fibrosis. Exosomal miR-122 exhibited a fair performance in discriminating advanced fibrosis especially in combination with fibrosis-4 score and transient elastography. In a subgroup of patients with a non-viral etiology of liver disease, the performance of exosomal miR-122 as a biomarker was greatly improved. Inhibition of miR-122 expression increased the proliferation of the human hepatic stellate cell line, LX-2, and upregulated the expression of various fibrosis related proteins. CONCLUSION: Exosomal miR-122 may serve as a useful non-invasive biomarker for liver fibrosis, especially in patients with non-viral etiologies of chronic liver disease.

Distal γ-C(sp3 )-H Olefination of Ketone Derivatives and Free Carboxylic Acids.

Reported herein is the distal γ-C(sp3 )-H olefination of ketone derivatives and free carboxylic acids. Fine tuning of a previously reported imino-acid directing group and using the ligand combination of a mono-N-protected amino acid (MPAA) and an electron-deficient 2-pyridone were critical for the γ-C(sp3 )-H olefination of ketone substrates. In addition, MPAAs enabled the γ-C(sp3 )-H olefination of free carboxylic acids to form diverse six-membered lactones. Besides alkyl carboxylic acids, benzylic C(sp3 )-H bonds also could be functionalized to form 3,4-dihydroisocoumarin structures in a single step from 2-methyl benzoic acid derivatives. The utility of these protocols was demonstrated in large scale reactions and diversification of the γ-C(sp3 )-H olefinated products.

Rational Development of Remote C-H Functionalization of Biphenyl: Experimental and Computational Studies.

A simple and efficient nitrile-directed meta-C-H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U-shaped template to achieve a molecular U-turn and assemble the large-sized cyclophane transition state for the remote C-H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta-C-H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta-selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand-containing Pd-Ag heterodimeric transition state (TS) favors the desired remote meta-selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non-directed meta-C-H activation. Substituted 2-pyridone ligands were found to be key in assisting the cleavage of the meta-C-H bond in the concerted metalation-deprotonation (CMD) process.

Ligand-Enabled γ-C(sp3)-H Activation of Ketones.

We report the first example of Pd(II)-catalyzed γ-C(sp3)-H activation of ketones directed by a practical 2,2-dimethyl aminooxyacetic acid auxiliary. 2-Pyridone ligands are identified to enable C(sp3)-H activation for the first time. A rare six-membered palladacycle intermediate is isolated and characterized to elucidate the reaction mechanism. Both (hetero)arylation and vinylation of γ-C(sp3)-H bonds are demonstrated. Sequential ß- and γ-C(sp3)-H (hetero)arylation of muscone showcases the utility of this method for late-stage diversification. A convenient Mn(II)-catalyzed auxiliary removal is also developed to further underscore the practicality of this transformation.

Versatile Alkylation of (Hetero)Aryl Iodides with Ketones via ß-C(sp3)-H Activation.

We report Pd(II)-catalyzed ß-C(sp3)-H (hetero)arylation of a variety of ketones using a commercially available 2,2-dimethyl aminooxyacetic acid auxiliary. Facile installation and removal of the auxiliary as well as its superior scope for both ketones and (hetero)aryl iodides overcome the significant limitations of the previously reported ß-C(sp3)-H arylation of ketones. The ready availability of ketones renders this reaction a broadly useful method for alkyl-(hetero)aryl coupling involving both primary and secondary alkyls.

Ginsenoside Rg3 restores hepatitis C virus-induced aberrant mitochondrial dynamics and inhibits virus propagation.

Hepatitis C virus (HCV) alters mitochondrial dynamics associated with persistent viral infection and suppression of innate immunity. Mitochondrial dysfunction is also a pathologic feature of direct-acting antiviral (DAA) treatment. Despite the high efficacy of DAAs, their use in treating patients with chronic hepatitis C in interferon-sparing regimens occasionally produces undesirable side effects such as fatigue, migraine, and other conditions, which may be linked to mitochondrial dysfunction. Here, we show that clinically prescribed DAAs, including sofosbuvir, affect mitochondrial dynamics. To counter these adverse effects, we examined HCV-induced and DAA-induced aberrant mitochondrial dynamics modulated by ginsenoside, which is known to support healthy mitochondrial physiology and the innate immune system. We screened several ginsenoside compounds showing antiviral activity using a robust HCV cell culture system. We investigated the role of ginsenosides in antiviral efficacy, alteration of mitochondrial transmembrane potential, abnormal mitochondrial fission, its upstream signaling, and mitophagic process caused by HCV infection or DAA treatment. Only one of the compounds, ginsenoside Rg3 (G-Rg3), exhibited notable and promising anti-HCV potential. Treatment of HCV-infected cells with G-Rg3 increased HCV core protein-mediated reduction in the expression level of cytosolic p21, required for increasing cyclin-dependent kinase 1 activity, which catalyzes Ser616 phosphorylation of dynamin-related protein 1. The HCV-induced mitophagy, which follows mitochondrial fission, was also rescued by G-Rg3 treatment. CONCLUSION: G-Rg3 inhibits HCV propagation. Its antiviral mechanism involves restoring the HCV-induced dynamin-related protein 1-mediated aberrant mitochondrial fission process, thereby resulting in suppression of persistent HCV infection. (Hepatology 2017;66:758-771).

Optimal level of the reference transducer for central venous pressure and pulmonary artery occlusion pressure monitoring in supine, prone, and sitting position.

To guarantee accurate measurement of central venous pressure (CVP) or pulmonary artery occlusion pressure (PAOP), proper positioning of a reference transducer is a prerequisite. We investigated ideal transducer levels in supine, prone, and sitting position in adults. Chest computed tomography images of 113 patients, taken in supine or prone position were reviewed. For supine position, distances between the back and the uppermost blood level of both atria and their ratios to the largest anteroposterior (AP) diameter of thorax were calculated. For prone position, same distances and ratios were calculated from the anterior chest. For sitting position, distances between the mid-sternoclavicular joint and the most cephalad blood level of both atria and their ratios to the sternal length were calculated. The ratio of the uppermost blood level of right atrium (RA) and left atrium (LA) to the largest AP diameter of thorax was 0.81 ± 0.04 and 0.59 ± 0.03 from the back in supine position. That calculated from the anterior chest in prone position was 0.54 ± 0.03 and 0.46 ± 0.03. The ratio of the most cephalad blood level of RA and LA to the sternal length was 0.70 ± 0.10 and 0.68 ± 0.09 from the mid-sternoclavicular joint in sitting position, which corresponded to the upper border of 4th rib. Optimal CVP transducer levels are at four-fifths of the AP diameter of thorax in supine position, at a half of that in prone position, and at upper border of the 4th sternochondral joint in sitting position. PAOP transducer levels are similar in prone and sitting position, except for supine position which is at three-fifths of the AP diameter of thorax.

Comparison of Supraclavicular and Infraclavicular Brachial Plexus Block: A Systemic Review of Randomized Controlled Trials.

BACKGROUND: Supraclavicular (SC) and infraclavicular (IC) brachial plexus block (BPB) are commonly used for upper extremity surgery. Recent clinical studies have compared the effect of SC- and IC-BPB, but there have been controversies over spread of sensory blockade in each of the 4 peripheral nerve branches of brachial plexus. METHODS: This study included a systemic review, using the Medline and EMBASE database from their inceptions through March 2016. Randomized controlled trials (RCTs) comparing SC- and IC-BPB were included. The prespecified primary outcome was the incidences of incomplete sensory blockade in each of the 4 terminal nerve branches of brachial plexus. Secondary outcome included the incidence of successful blockade, performance time, onset of sensory block, duration of analgesia, and complication rates. RESULTS: Ten RCTs involving 676 patients were included. Pooled analyses showed the incidence of incomplete block at 30 minutes in radial nerve territory was significantly higher in IC-BPB, favoring SC-BPB (risk ratio 0.39; 95% confidence interval [0.17-0.88], P = .02, I = 0%). However, subgroup analysis according to the number of injections of IC-BPB showed that double or triple injections IC-BPB yielded no difference in the incomplete radial block. Furthermore, the incidence of incomplete ulnar block at 30 minutes was significantly lower in IC-BPB when using double or triple injection IC-BPB. There was no difference in the secondary outcomes between SC- and IC-BPB groups, with the exception of complication rates. The incidence of paresthesia/pain on local anesthetic injection, phrenic nerve palsy, and Horner syndrome was significantly higher in the SC group, favoring IC-BPB. CONCLUSIONS: This meta-analysis demonstrated that IC-BPB showed a significantly high incidence of incomplete radial nerve sensory block at 30 minutes, which may be avoided by double or triple injection. Furthermore, IC-BPB with multiple injection technique showed significantly lower incidence of incomplete ulnar block than SC-BPB. There were no differences in the incidence of successful blockade, block onset, and duration of analgesia between SC- and IC-BPB. Procedure-related paresthesia/pain and adjacent nerve-related complications were more frequent in SC-BPB. However, because of the small sample size, publication bias remains a concern when interpreting our results. Further studies with sufficient sample size and reporting large number of outcomes are required.

The lack of relationship between intracranial pressure and cerebral ventricle indices based on brain computed tomography in patients undergoing ventriculoperitoneal shunt.

BACKGROUND: In this study we investigated whether cerebral ventricle indices based on brain computed tomography (CT) scans are reliable for predicting intracranial pressure (ICP) in hydrocephalic patients. METHODS: Electronic medical records of 221 patients undergoing ventriculoperitoneal shunt due to hydrocephalus were retrospectively reviewed. Cerebral ventricle indices including Evans' index, third ventricle index, cella media index, and ventricular score were calculated from transverse diameters measured at various levels on preoperative brain CT scans. ICP was considered as CSF opening pressure. Patients were categorized into three groups: communicating hydrocephalus, non-communicating hydrocephalus, and normal pressure hydrocephalus (NPH). The non-communicating hydrocephalus group was further divided according to the obstruction site; aqueduct, fourth ventricle outlet, third ventricle, and the foramen of Monro. The primary endpoint was the extent of the correlation between cerebral ventricle indices and ICP in each hydrocephalus group. RESULTS: No cerebral ventricle index correlated with ICP in patients with communicating hydrocephalus (n = 113) and NPH (n = 62). In the non-communicating hydrocephalus group (n = 46), only the third ventricle index revealed moderate negative correlation with ICP (r = -0.395, p < 0.01). In subgroup analyses, the third ventricle index showed a strong negative relationship with ICP only in patients with the third ventricle obstruction (r = -0.779, p < 0.05). CONCLUSIONS: In this study we showed that although an inverse correlation existed between ICP and the third ventricle index only in patients with non-communicating hydrocephalus due to obstruction of the third ventricle, cerebral ventricle indices based on brain CT scan were non-reliable predictors of ICP in hydrocephalic patients.

Development of a modified straw method for vitrification of in vitro-produced bovine blastocysts and various genes expression in between the methods.

This study evaluated a modified plastic straw loading method for vitrification of in vitro-produced bovine blastocysts. A modified straw was used with a depressed area on its inner surface to which embryos attach. In vitro-produced blastocysts were randomly assigned into three groups: (i) blastocysts attached to the inner surface of a plastic straw (aV), (ii) blastocysts attached to the inner surface of a modified plastic straw (maV), and (iii) non-vitrified blastocysts (control). The recovery rates were not significantly different between aV and maV groups (95.8% vs. 94.3%). The post-thaw survival rate did not significantly differ between aV and maV groups (86.4% vs. 88.2%). The total cell numbers of blastocyst was higher in control than in aV and maV groups (142 ± 21.8 vs. 117 ± 29.7 and 120 ± 25.2; P < 0.05), but not significantly differ between aV and maV groups. The mRNA levels of pro-apoptosis related genes Bax and Caspase-3 were higher in aV and maV than in control (P < 0.05). By contrast, the mRNA levels of anti-apoptotic genes Bcl-2 and Mcl-1 and of antioxidant-related genes MnSOD and Prdx5 were lower in aV and maV than in control (P < 0.05). Confocal microscopy analysis of Golgi apparatus and mitochondria showed that the fluorescence intensity of Golgi apparatus and mitochondria was higher in control than in aV and maV groups. In conclusion, both aV and maV methods can be used to successfully vitrify IVP blastocysts, with maV method to be preferable because of its easiness in embryo loading.

Postthaw survival of in vitro-produced bovine blastocysts loaded onto the inner surface of a plastic vitrification straw.

In this study, we investigated whether vitrification of an embryo by attachment to the inner surface of a plastic straw, which requires a small volume of vitrification solution, improves the survival of thawed embryos. In vitro-produced Korean native cattle blastocysts were randomly assigned into four groups: (1) blastocysts attached to the inner surface of a plastic straw (aV); (2) blastocysts loaded into the column of a plastic straw (cV); (3) blastocysts directly dropped into liquid nitrogen (dV); and (4) nonvitrified blastocysts (control). The postthaw recovery rate did not significantly differ among the aV, dV, and cV groups (98.3% vs. 81.5% vs. 91.4%). The postthaw survival rate was greater in the control, aV, and dV groups than in the cV group (100%, 87.7%, and 81.8% vs. 26.4%, P < 0.05), but did not significantly differ among the control, aV, and dV groups. The total number of cells per blastocyst did not significantly differ among the groups (134.4 ± 38.9 in control vs. 114 ± 48.1 in aV, 105.6 ± 33.9 in dV, and 102 ± 35.1 in cV group). However, the number of apoptotic cells per blastocyst was higher in the dV and cV groups than in the control group (10.9 ± 9.6 and 14.5 ± 9.5 vs. 0.4 ± 1.4; P < 0.05), but did not significantly differ between the control and aV groups (0.4 ± 1.4 vs. 6.6 ± 9.5). In addition, the blastocoel of each blastocyst was left intact or was mechanically punctured to reduce its volume, and the blastocysts were then vitrified using the aV method. At 12 hours after thawing, the re-expansion rate did not significantly differ among the control, punctured aV, and nonpunctured aV groups (93.3% vs. 85.2% vs. 82.8%). However, at 24 hours after thawing, the hatching rate was greater in the control and punctured aV groups than in the nonpunctured aV group (75% and 62.9% vs. 37.1%; P < 0.05). The total number of cells per blastocyst was greater in the control group than in the nonpunctured aV group (143 ± 37.2 vs. 94.5 ± 18.6; P < 0.05), but did not significantly differ between the control and punctured aV groups (143 ± 37.2 vs. 119.4 ± 19.7). The number of apoptotic cells per blastocyst was greater in the nonpunctured aV group than in the control and punctured aV groups (11.3 ± 6.1 vs. 5.9 ± 5.8 and 6.3 ± 4.4; P < 0.05). Taken together, the data show that the aV method improved the survival and quality of vitrified-thawed blastocysts. Furthermore, puncture of the blastocoel increased the hatching rate and reduced the number of apoptotic cells in vitrified-thawed blastocysts generated using the aV method.