Tin(II) Chloride-Catalyzed Direct Esterification and Amidation of tert-Butyl Esters Using α,α-Dichlorodiphenylmethane Under Mild Conditions.

A practical one-pot synthesis of esters and amides from tert-butyl esters via acid chloride was developed. Reactions of tert-butyl esters with α,α-dichlorodiphenylmethane as the chlorinating agent and SnCl2 as catalyst-generated acid chloride intermediates in situ were subsequently used in reactions with a variety of alcohols and amines to afford the corresponding esters and amides in high yields under mild reaction conditions. This catalytic synthetic procedure offers an effective strategy for the facile esterification and amidation of tert-butyl esters.

Direct transformation of benzyl esters into esters, amides, and anhydrides using catalytic ferric(III) chloride under mild conditions.

A facile one-pot transformation of benzyl esters into esters, amides, and anhydrides is described. α,α-Dichlorodiphenylmethane and FeCl3 were employed as the chlorinating agent and catalyst respectively to convert benzyl esters into acid chloride intermediates, which directly reacted with alcohols, amines, and carboxylic acids. Various esters, amides, and anhydrides were readily obtained with high yields under mild conditions. This method is promising for the practical synthesis of esters, amides, and anhydrides from benzyl esters.

Recent Advances of 68Ga-Labeled PET Radiotracers with Nitroimidazole in the Diagnosis of Hypoxia Tumors.

Positron emission tomography (PET) is a noninvasive molecular imaging method extensively applied in the detection and treatment of various diseases. Hypoxia is a common phenomenon found in most solid tumors. Nitroimidazole is a group of bioreducible pharmacophores that selectively accumulate in hypoxic regions of the body. Over the past few decades, many scientists have reported the use of radiopharmaceuticals containing nitroimidazole for the detection of hypoxic tumors. Gallium-68, a positron-emitting radioisotope, has a favorable half-life time of 68 min and can be conveniently produced by 68Ge/68Ga generators. Recently, there has been significant progress in the preparation of novel 68Ga-labeled complexes bearing nitroimidazole moieties for the diagnosis of hypoxia. This review provides a comprehensive overview of the current status of developing 68Ga-labeled radiopharmaceuticals with nitroimidazole moieties, their pharmacokinetics, and in vitro and in vivo studies, as well as PET imaging studies for hypoxic tumors.

Recent Advances in Synthetic Routes to Azacycles.

A heterocycle is an important structural scaffold of many organic compounds found in pharmaceuticals, materials, agrochemicals, and biological processes. Azacycles are one of the most common motifs of a heterocycle and have a variety of applications, including in pharmaceuticals. Therefore, azacycles have received significant attention from scientists and a variety of methods of synthesizing azacycles have been developed because their efficient synthesis plays a vital role in the production of many useful compounds. In this review, we summarize recent approaches to preparing azacycles via different methods as well as describe plausible reaction mechanisms.

Facile tin(II)-catalyzed synthesis of N-heterocycles from dicarboxylic acids and arylamines.

A novel efficient transformation reaction of dicarboxylic acids into N-aryl-substituted azacycles is described. In this synthetic procedure, both catalytic SnCl2 and phenylsilane were used as crucial reagents for reaction of arylamines with dicarboxylic acids to produce the desired azacycles. Using this SnCl2-catalyzed synthetic method, various N-aryl-substituted azacycles were successfully prepared from arylamines with dicarboxylic acids in high yield. This practical synthetic method using catalytic SnCl2 can provide a useful approach for preparation of the desired azacycle products from many available dicarboxylic acid starting materials.

Design, synthesis and anti-inflammatory activity of imidazol-5-yl pyridine derivatives as p38α/MAPK14 inhibitor.

P38α/MAPK14 is intracellular signalling regulator involved in biosynthesis of inflammatory mediator cytokines (TNF-α, IL-1, IL-6, and IL-1b), which induce the production of inflammatory proteins (iNOS, NF-kB, and COX-2). In this study, drug repurposing strategies were followed to repositioning of a series of B-RAF V600E imidazol-5-yl pyridine inhibitors to inhibit P38α kinase. A group 25 reported P38α kinase inhibitors were used to build a pharmacophore model for mapping the target compounds and proving their affinity for binding in P38α active site. Target compounds were evaluated for their potency against P38α kinase, compounds 11a and 11d were the most potent inhibitors (IC50 = 47 nM and 45 nM, respectively). In addition, compound 11d effectively inhibited the production of proinflammatory cytokinesTNF-α, 1L-6, and 1L-1ß in LPS-induced RAW 264.7 macrophages with IC50 values of 78.03 nM, 17.6 µM and 82.15 nM, respectively. The target compounds were tested for their anti-inflammatory activity by detecting the reduction of Nitric oxide (NO) and prostaglandin (PGE2) production in LPS-stimulated RAW 264.7 macrophages. Compound 11d exhibited satisfied inhibitory activity of the production of PGE2 and NO with IC50 values of 0.29 µM and 0.61 µM, respectively. Molecular dynamics simulations of the most potent inhibitor 11d were carried out to illustrate its conformational stability in the binding site of P38α kinase.

Synthesis and evaluation of multivalent nitroimidazole-based near-infrared fluorescent agents for neuroblastoma and colon cancer imaging.

Hypoxia is one of key characteristics of microenvironments of solid tumors, and evaluation of hypoxia status in solid tumors is important to determine cancer stage and appropriate treatment. In the present study, novel, multivalent, near-infrared (NIR) fluorescent imaging agents were developed to measure tumor hypoxia. These agents were synthesized using an amino acid as a backbone to connect mono-, bis-, or tris-2-nitroimidazole as a hypoxia-sensitive moiety to enhance uptake by the tumor and to attach sulfo-Cyanine 5.5 as an NIR fluorophore to visualize tumor accumulation. Studies of physical characteristics demonstrated that the novel NIR imaging agents showed suitable optical properties for in vitro and in vivo imaging and were stable in serum. In vitro cellular uptake studies in SK-N-BE(2) and SW620 cell lines demonstrated that NIR imaging agents bearing 2-nitroimidazole structures showed significantly higher tumor uptake in hypoxic cells than in normoxic cells. Moreover, in vivo optical imaging studies using SK-N-BE(2) and SW620 xenografted mice demonstrated that novel, multivalent, 2-nitroimadazole NIR imaging agents with two or three 2-nitroimidazole moieties showed higher uptake in tumor than the control agents with only one 2-nitroimidazole. These observations suggest that novel, multivalent, NIR agents could serve as potential optical imaging agents for evaluating tumor hypoxia.

Visible-Light-Induced Catalytic Selective Halogenation with Photocatalyst.

Halide moieties are essential structures of compounds in organic chemistry due to their popularity and wide applications in many fields such as natural compounds, agrochemicals, and pharmaceuticals. Thus, many methods have been developed to introduce halides into various organic molecules. Recently, visible-light-driven reactions have emerged as useful methods of organic synthesis. Particularly, halogenation strategies using visible light have significantly improved the reaction efficiency and reduced toxicity, as well as promoted reactions under mild conditions. In this review, we have summarized recent studies in visible-light-mediated halogenation (chlorination, bromination, and iodination) with photocatalysts.

Evaluation of the Inhibitory Effects of Pyridylpyrazole Derivatives on LPS-Induced PGE2 Productions and Nitric Oxide in Murine RAW 264.7 Macrophages.

A series of thirteen triarylpyrazole analogs were investigated as inhibitors of lipopolysaccharide (LPS)-induced prostaglandin E2 (PGE2) and nitric oxide (NO) production in RAW 264.7 macrophages. The target compounds 1a-m have first been assessed for cytotoxicity against RAW 264.7 macrophages to determine their non-cytotoxic concentration(s) for anti-inflammatory testing to make sure that the inhibition of PGE2 and NO production would not be caused by cytotoxicity. It was found that compounds 1f and 1m were the most potent PGE2 inhibitors with IC50 values of 7.1 and 1.1 µM, respectively. In addition, these compounds also showed inhibitory effects of 11.6% and 37.19% on LPS-induced NO production, respectively. The western blots analysis of COX-2 and iNOS showed that the PGE2 and NO inhibitory effect of compound 1m are attributed to inhibition of COX-2 and iNOS protein expression through inactivation of p38.

Inhibitory effects of triarylpyrazole derivatives on LPS-induced nitric oxide and PGE2 productions in murine RAW 264.7 macrophages.

In this article, a series of 22 triarylpyrazole derivatives were evaluated for in vitro antiinflammatory activity as inhibitors of nitric oxide (NO) and prostaglandin E2 (PGE2) release induced by lipopolysaccharide (LPS) in murine RAW 264.7 macrophages. The synthesized compounds 1a-h, 2a-f and 3a-h were first examined for their cytotoxicity for determination of the non-toxic concentration for antiinflammatory screening, so that the inhibitory effects against NO and PGE2 production were not caused by non-specific cytotoxicity. Compounds 1h and 2f were the most active PGE2 inhibitors with IC50 values of 2.94 µM and 4.21 µM, respectively. Western blotting and cell-free COX-2 screening revealed that their effects were due to inhibition of COX-2 protein expression. Moreover, compound 1h exerted strong inhibitory effect on the expression of COX-2 mRNA in LPS-induced murine RAW 264.7 macrophages.

Practical direct synthesis of N-aryl-substituted azacycles from N-alkyl protected arylamines using TiCl4 and DBU.

A novel transformation of N-alkyl protected arylamines and cyclic ethers into N-aryl substituted azacycles is described. Alkyl groups have been used for the protection of amines in organic syntheses. In this synthesis, N-alkyl protected arylamines were reacted with cyclic ethers in the presence of TiCl4 and DBU, crucial reagents affording five- and six-membered azacycles. In particular, utilization of the novel TiCl4/DBU-mediated reaction allows various N-alkyl protected arylamines such as N-methyl-, N-ethyl-, N-isopropyl, and N-tert-butyl arylamines to be readily converted into N-aryl substituted azacycles in high yields. This practical approach using various N-alkyl arylamines leads to the efficient preparation of azacycles.

Synthesis and Evaluation of Multifunctional Fluorescent Inhibitors with Synergistic Interaction of Prostate-Specific Membrane Antigen and Hypoxia for Prostate Cancer.

Prostate cancer is one of the most common cancers in the world. It is widely known that prostate-specific membrane antigen (PSMA) is highly expressed in prostate cancer, and hypoxia is a common characteristic of many solid tumors, including prostate cancer. In this study, we designed multifunctional fluorescent inhibitors to target PSMA and tumor hypoxia in order to increase the tumor uptake of inhibitors. Novel PSMA inhibitors were prepared using lysine as the backbone to connect three different functional groups: the glutamate-urea-lysine (GUL) structure for inhibiting PSMA, 2-nitroimidazole for the hypoxia-sensitive moiety, and a near-infrared fluorophore (sulfo-Cyanine 5.5). According to the in vitro PSMA binding assay, novel fluorescent inhibitors were demonstrated to have nanomolar binding affinities. Multifunctional inhibitor 2 with one 2-nitroimidazole had a similar inhibitory activity to inhibitor 1 that did not contain the hypoxia targeting moiety, but multifunctional inhibitor 3 with two 2-nitroimidazoles showed lower inhibitory activity than inhibitor 1 due to the bulky structure of the hypoxia-sensitive group. However, in vivo optical imaging and ex vivo biodistribution studies indicated that both multifunctional inhibitors 2 and 3 had higher accumulation in tumors than inhibitor 1 due to a synergistic combination of PSMA and hypoxia targeting moieties. These observations suggest that this novel multifunctional strategy might be a promising approach to improve the diagnosis and therapy of prostate cancer.

Metal-Free Synthesis of N-Aryl-Substituted Azacycles from Cyclic Ethers Using POCl3.

A facile method for the synthesis of N-aryl-substituted azacycles from arylamines and cyclic ethers has been developed. In this study, arylamines were treated with cyclic ethers in the presence of POCl3 and DBU to provide five- and six-membered azacycles. Using this method, various azacycloalkanes, isoindolines, and tetrahydroisoquinolines were prepared in high yields. This synthetic method offers an efficient approach to the production of azacycles from cyclic ethers.

Practical preparation of diphenylmethyl ethers from 2-diphenylmethoxypyridine using catalytic iron(iii) chloride.

A novel facile synthetic method for producing diphenylmethyl (DPM) ethers from 2-diphenylmethoxypyridine was developed. A variety of DPM ethers was successfully achieved with high yield via treatment of alcohols with 2-diphenylmethoxypyridine in the presence of catalytic FeCl3. The procedure is a practical and efficient synthetic procedure to protect various alcohols, and it can be applied to prepare bioactive compounds.

Synthesis and evaluation of novel potent TSPO PET ligands with 2-phenylpyrazolo[1,5-a]pyrimidin-3-yl acetamide.

Translocator protein (TSPO) expression is closely related with neuroinflammation and neuronal damage which might cause several central nervous system diseases. Herein, a series of TSPO ligands (11a-c and 13a-d) with a 2-phenylpyrazolo[1,5-a]pyrimidin-3-yl acetamide structure were prepared and evaluated via an in vitro binding assay. Most of the novel ligands exhibited a nano-molar affinity for TSPO, which was better than that of DPA-714. Particularly, 11a exhibited a subnano-molar TSPO binding affinity with suitable lipophilicity for in vivo brain studies. After radiolabeling with fluorine-18, [18F]11a was used for a dynamic positron emission tomography (PET) study in a rat LPS-induced neuroinflammation model; the inflammatory lesion was clearly visualized with a superior target-to-background ratio compared to [18F]DPA-714. An immunohistochemical examination of the dissected brains confirmed that the uptake location of [18F]11a in the PET study was consistent with a positively activated microglia region. This study proved that [18F]11a could be employed as a potential PET tracer for detecting neuroinflammation and could give possibility for diagnosis of other diseases, such as cancers related with TSPO expression.

Synthesis of novel multivalent fluorescent inhibitors with high affinity to prostate cancer and their biological evaluation.

Prostate-specific membrane antigen (PSMA) is an important biological target for therapy and diagnosis of prostate cancer. In this study, novel multivalent PSMA inhibitors with glutamate-urea-lysine structures were designed to improve inhibition characteristics. Precursors of the novel inhibitors were prepared from glutamic acid with di-tert-butyl ester. A near-infrared molecular dye, sulfo-Cy5.5, was introduced into the precursors to generate the final PSMA fluorescent inhibitors, compounds 12-14, to visualize prostate cancer. Biological behaviors of the inhibitors were evaluated using in vitro inhibition assays, in vivo fluorescent imaging, and ex vivo biodistribution assays. Ki values from inhibition studies indicated that dimeric inhibitor 13 with a glutamine linker showed approximately 3-fold more inhibitory activity than monomeric inhibitor 12. According to other biological studies using a mouse model of prostate cancer, dimeric inhibitor compounds 13 and 14 had higher tumor accumulation than the monomer. However, glutamine-based dimeric inhibitor 13 showed lower liver uptake than dimeric inhibitor 14, which had a benzene structure. Thus, these studies suggest that glutamine-based dimeric inhibitor 13 can be a promising optical inhibitor of prostate cancer.

Facile one-pot synthesis of unsymmetrical ureas, carbamates, and thiocarbamates from Cbz-protected amines.

A novel one-pot synthesis of unsymmetrical ureas, carbamates and thiocarbamates from Cbz-protected amines has been developed. In the presence of 2-chloropyridine and trifluoromethanesulfonyl anhydride, isocyanates are generated in situ, which facilitate rapid reaction with amines, alcohols, and thiols to afford the corresponding ureas, carbamates and thiocarbamates in high yields.

Lack of functional KL-VS polymorphism of the KLOTHO gene in the Korean population.

The functional variant of the Klotho "KL-VS" stretch, which includes six polymorphisms in linkage disequilibrium, is reportedly associated with healthy aging and longevity in European and American populations. Among Asian populations, this variant has been observed in the Indian population but not in the Iranian population. An association between KL-VS polymorphism and aging has not been reported in Koreans. To investigate whether the KL-VS polymorphism could be associated with healthy aging and longevity in a Korean population, we analyzed genotype and allele frequencies of the KL-VS variant in a large Korean population sample. The KL-VS variant was not found in 874 Korean individuals. Thus, it is not possible to test its association to aging in the East Asian populations.

Photoassisted one-step aerosol fabrication of zwitterionic chitosan nanoparticles.

Zwitterionic chitosan nanoparticles (ZCNPs) were conveniently obtained by a one-step aerosol method, and their potential for the production of biocompatible materials was investigated. A low-molecular-weight chitosan was conjugated with succinic anhydride to produce zwitterionic chitosan (ZC). Collison-atomized ZC droplets were simultaneously UV-irradiated and dried in a tube furnace in a one-step aerosol process to produce particles. The observed cytotoxicities of ZCNPs (85 ± 3.9% cell viability) were similar to unmodified chitosan nanoparticles (CNPs, 88 ± 6.6%) and UV-irradiated ZCNPs (83 ± 3.3%). The aerosol process described in this work allowed facile production and modification of CNPs, which could then be employed for biomedical purposes.

Recent Progress in Synthesis of 99mTc-labeled Complexes with Nitroimidazoles as SPECT Probes for Targeting Tumor Hypoxia.

The majority of solid tumors have hypoxia, or low oxygen levels, which is one of the hallmarks of cancer. Hypoxia was found to relate to cancer metastases and resistance to therapies, therefore, detection of hypoxia plays an important role in the process of cancer prognosis and treatment. Single-photon emission computed tomography (SPECT) is a non-invasive imaging technique using gamma-emitting radiopharmaceuticals to visualize biological activities within the body. SPECT is also applied for the detection of tumor hypoxia with the development of hypoxia-targeting radiopharmaceuticals. Radiopharmaceuticals containing nitroimidazole moieties have received increasing attention due to their bio-reducible characteristics which make the radiopharmaceuticals accumulate in the hypoxia regions. This review summarizes the recent development of 99mTc-labeled radiopharmaceuticals bearing nitroimidazoles for SPECT imaging of tumor hypoxia including the synthetic methods and results of animal studies.