Search

Quantification of the steric and electronic properties of ligands is an important task for the development of highly effective chemical transformations when using a metal complex as a catalyst. In ...

In this study, we developed a method for etherification via aromatic substitution at the ipso-position of an electron-withdrawing group (EWG) that exists at the meta-position of another EWG. To heighten the reactivity of the substitution reaction, we added a

In this study, a well-defined, novel NHC-Ni complex was developed and used to catalyze the N-arylation of alkyl- and arylamines with arylboronic acids in a rare version of Chan-Lam coupling. Although the same coupling using copper catalysts has been widely studied, the nickel-catalyzed version is rare and normally requires 10–20 mol% catalyst loading. This novel NHC-Ni complex in combination with 4,4′-dimethyl-2,2′-bipyridine, however, proved to be an effective catalyst that lowered the required catalyst loading to only 2.0 mol%.

In this study, mild conditions for aromatic substitutions during the syntheses of aryl ethers were developed. In the reaction conditions, the choices of solvent, base, and the sequence for the addition of the reagents proved important. A wide variety of alcohols were used directly as nucleophiles and smoothly reacted with aryl chlorides that possessed either a nitro or a cyano group at either the ortho- or para-position. Controlled experiments we performed suggested that the reaction underwent a charge-transfer process mediated by a combination of DMF and

A novel type of molecularly imprinted polymer (MIP), N-benzoyl-(S)-valine anilide-imprinted polymer (IP-2), was prepared using hydrogen-bonding interactions as a main force in the pre-polymerization step. The performance of the IP-2 was evaluated via batch procedure and compared with a (S)-valine anilide-imprinted polymer (IP-1) that was prepared using an ionic interaction that is stronger than hydrogen bonding. Although both polymers showed a preferential adsorbability for (S)-amino acid derivatives, different performances were observed in terms of adsorbability and enantioselectivity. In addition, the IP-2 was able to recognize the enantiomer of a valine-derived chiral catalyst. This phenomenon was applied to a chiral amplification reaction, and a highly selective asymmetric Mannich-type amination was achieved using the combination of a racemic catalyst and a MIP.

The combination of a "rigid" chiral bicyclic cis-1,2-diamine skeleton with steric bulkiness and a "flexible" achiral linker was newly designed as a bifunctional organocatalyst framework and it showed excellent catalytic activity of up to 0.05 mol%, accompanied by the reversal of enantioselection depending on the position of the linker, in an amine-thiourea organocatalyzed asymmetric Michael reaction.

In addition to phosphanes, olefins, amines, and amides, over the past two decades N-heterocyclic carbene (NHC) has emerged as a useful alternative ligand. Based on a number of derivatization studies on NHC ligands, imidazol-2-ylidene and imidazolin-2-ylidene became the standard heterocyclic form, and bulky substituents have commonly been introduced on the nitrogen(s) adjacent to carbenic carbons. Our group previously developed NHCs equipped with noncarbenic carbons with a bicyclic architecture that gives them unique steric properties that make them bulky but accessible. In this study, we synthesized a novel type of NHC ligand that possesses a bicyclo[2.2.1]heptane architecture, and we compared five derivatives using copper-catalyzed allylic arylations with aryl Grignard reagents. The regioselectivity of the substitution obviously indicates that a phenyl ring over an active site has a characteristic effect on the resultant copper catalysts when γ-substitution is the major pathway.

In this study, nickel-catalyzed coupling reactions between arylhalides and tert-alkyl Grignard reagents were developed. Our original bicyclic NHC ligands reduced the formation of isomerized products, and we found that NMP as a co-solvent suppressed the reduction process. Under the optimal conditions we developed, the catalyst loading was lowered to 0.5 mol %, and catalyst loading using ortho-substituted aryl bromides was also applicable at the level of 2.0 mol %.

Imidazol-2-ylidene and imidazolin-2-ylidene are frequently employed as the core structures of N-heterocyclic carbene (NHC) ligands, because these have two nitrogen sites adjacent to carbenic carbons. The electronic and steric effects of N-substituents to a bound metal have been aptly studied, and bulky substituents have commonly been introduced on nitrogen(s). However, too much bulkiness can sometimes result in an ineffectiveness of the hindered substrates. In this study, we thoroughly compared our original bicyclic NHC, which has bulky substituents on its noncarbenic carbons, with ubiquitous NHC ligands to probe its steric properties. A well-defined bicyclic NHC-CuCl complex was successfully synthesized and applied to the copper-catalyzed borylations of aryl halides at ambient temperature. A bicyclic NHC-CuCl proved to be a better catalyst than commonly used NHC ligand-Cu complexes, particularly for sterically hindered substrates, which suggested that the bicyclic NHC ligand offered a bulky but accessible environment to the bound copper.

Prescriptions of non-benzodiazepine sedative hypnotics, e.g. zolpidem, for insomnia in elderly subjects 80 years of age or older have markedly increased in the USA. However, a meta-analysis of the risks and benefits of hypnotics in older people reported the benefits associated with hypnotics use are outweighed by the risks. This study aimed to investigate the safety of zolpidem administration in extremely old elderly.The prevalence of adverse reactions to zolpidem was investigated in a subpopulation of participants in the Drug Event Monitoring project of the Japan Pharmaceutical Association. A total of 1011 (316 males and 695 females) zolpidem users, including 261 (25.8%) subjects 80 years of age or older without cognitive or mental complications, were eligible for the analysis.The elderly and female patients were prescribed significantly lower doses of zolpidem than their counterparts. Adverse symptoms after the last prescription were reported by 60 (5.9%) subjects. The most common symptoms were impaired balance and/or falls (1.8%) and morning drowsiness (1.3%). The multiple logistic regression analyses showed that subjects 80 years of age or older were at lower risk of adverse symptoms (odds ratio 0.39, 95% confidence intervals: 0.17-0.88).Our findings in a real-world clinical setting suggest that low-dose zolpidem can be safely prescribed to subjects 80 years of age or older without cognitive or mental complications.

The desymmetrization of a meso molecule was used for the development of a chiral N-heterocyclic carbene (NHC) ligand. This chiral NHC was then successfully applied to a copper-catalyzed asymmetric allylic arylation with Grignard reagents. The level of stereocontrol was improved to 89 % ee via derivatization studies. The synthesized copper catalyst was effective at the level of 0.05 mol % loading for gram-scale reactions.

Meta-analyses of randomized clinical trials have reported that dipeptidyl peptidase IV (DPP-4) inhibitors are well tolerated and that the incidence of hypoglycemia with the use of DPP-4 inhibitors is similar to that observed with placebos. However, in general, provider-oriented methods using medical record reviews offer lower rates of non-serious, symptomatic adverse drug reactions (ADRs) than patient-oriented methods. Moreover, severe hypoglycemia occurred in three clinical trials using sitagliptin, but in two of these trials this phenomenon has been previously described only in the drug application data in the US.The aim of this study was to assess the profile of patient-reported symptomatic ADRs under DPP-4 inhibitor therapy and to detect risk factors for hypoglycemic and non-hypoglycemic adverse symptoms in daily clinical practice.We analyzed a subpopulation of participants in the Drug Event Monitoring (DEM) project of the Japan Pharmaceutical Association. An anonymous survey was conducted in February 2012 to assess the self-perception of adverse symptoms during a median 28 (4-88) days after the last prescription of DPP-4 inhibitors by means of interviews of pharmacists using structured questionnaires.A total of 864 males and 686 females were included. The prescribed DPP-4 inhibitors included sitagliptin (75.4 %), alogliptin (15.5 %), vildagliptin (8.8 %) and linagliptin (0.3 %). Mild hypoglycemic symptoms were reported by 34 individuals (2.2 %) receiving monotherapy of sitagliptin (10/402) or alogliptin (3/65), or combination therapy of sitagliptin (15/767) or alogliptin (6/176) with other hypoglycemic agents. In the multiple regression model, hypoglycemic symptoms were found to be significantly associated with liver disease, female sex and alcohol consumption more than three times per week. Non-hypoglycemic symptoms were reported by 57 individuals (3.7 %), the most common symptoms of which were gastrointestinal symptoms (2.1 %). Combination therapy was only found to be associated with nonhypoglycemic symptoms.The present study suggested that hypoglycemic symptoms under therapy with sitagliptin or alogliptin may be associated with liver disease, female sex and alcohol consumption, all of which are potentially capable of leading to poor gluconeogenesis because they decrease the counter-regulatory hormonal responses to hypoglycemia.

A novel type of N-heterocyclic carbene ligand, with a bicyclic motif at the non-carbenic carbons of an imidazolin-2-ylidene core, has been developed. This type of ligand formed an air and moisture stable silver complex even with N,N′-dimethyl NHC. Allylic arylation with a Grignard reagent catalyzed by copper complexes of the NHC ligands proceeded preferentially at the γ-position, indicating the effective steric shielding ability of this framework.

We evaluated the adsorbability and selectivity of (S)-valine anilide imprinted molecularly imprinted polymer (MIP) using a batch procedure that is both independent and precise. This study revealed important information about the relationship between the performance of MIPs and experimental factors such as the components of MIP synthesis and a reaction solvent. Herein, we also describe the problems associated with the preparation of a "non-imprinted polymer," which is often used to evaluate the effect of a template molecule, and we propose a new type of reference polymer, "blank polymer."

Imidazol-2-ylidene and imidazolin-2-ylidene are frequently employed as the core structures of N-heterocyclic carbene (NHC) ligands, because these have two nitrogen sites adjacent to carbenic carbons. The electronic and steric effects of N-substituents to a bound metal have been aptly studied, and bulky substituents have commonly been introduced on nitrogen(s). However, too much bulkiness can sometimes result in an ineffectiveness of the hindered substrates. In this study, we thoroughly compared our original bicyclic NHC, which has bulky substituents on its noncarbenic carbons, with ubiquitous NHC ligands to probe its steric properties. A well-defined bicyclic NHC-CuCl complex was successfully synthesized and applied to the copper-catalyzed borylations of aryl halides at ambient temperature. A bicyclic NHC-CuCl proved to be a better catalyst than commonly used NHC ligand-Cu complexes, particularly for sterically hindered substrates, which suggested that the bicyclic NHC ligand offered a bulky but accessible environment to the bound copper.

Background Skin maceration is recognized as a risk factor for the development of certain skin lesions. In health care settings, incontinence-associated skin maceration is highly prevalent in the elderly. However, the effect of senescence on maceration has not been fully elucidated. Objective To reveal the enhancement of the maceration-induced ultrastructural alteration and barrier function of the epidermis by aging. Methods Skin maceration was reproduced by exposure to agarose gel in human and rat. The ultrastructural alterations in human and rat tissue were observed by transmission electron microscopy. The skin barrier function was evaluated by noninvasive methods in human, and by the transdermal penetration of small- and large-fluorescent molecules in rat. In order to reveal the effect of aging on the skin maceration, we compared these parameters between young and aged rats. Results In macerated skin, we observed expansion of the interstices of the stratum corneum, spinosum, and basale of the epidermis; disruption of the intercellular lipid structure in the stratum corneum; a decreased number of cell processes in the stratum spinosum and basale. The transdermal penetration test in the rat using two types of fluorescein indicated that maceration disrupted skin barrier function. Furthermore, senescence-enhanced ultrastructural and functional alterations were revealed in the rodent studies. Conclusion This study demonstrates that aging enhances skin maceration. Considering that maceration is a risk factor for the skin damage, the development of technology to promote skin barrier recovery after maceration in the elderly is warranted.

Although some evidence suggests that women may be at greater risk for hypoglycemia, no conclusion has been reached, and female sex has not been taken into account in antidiabetic drug-induced hypoglycemia. This study aimed to determine whether females are at a higher risk of sulfonylurea (SU)-associated hypoglycemia in daily clinical practice. The incidence of adverse reactions of SU was investigated in 2119 Japanese patients who participated in the Drug Event Monitoring project of the Japan Pharmaceutical Association, which was conducted in Kumamoto prefecture. A multiple logistic regression analysis was used to determine the association between the incidence of hypoglycemic symptoms and female sex, with adjusted odds ratios (ORs) and 95 % confidence intervals (95 % CIs). Female sex was found to be significantly associated with hypoglycemic symptoms (female vs. male; OR 2.04; 95 % CI 1.22–3.41; p = 0.007). The concomitant use of other antihyperglycemic agents (≥2 vs. 0 concomitant drug; OR 2.80; 95 % CI 1.17–6.67; p = 0.021), a shorter duration of diabetes medication (

The desymmetrization of a meso molecule was used for the development of a chiral N-heterocyclic carbene (NHC) ligand. This chiral NHC was then successfully applied to a copper-catalyzed asymmetric allylic arylation with Grignard reagents. The level of stereocontrol was improved to 89 % ee via derivatization studies. The synthesized copper catalyst was effective at the level of 0.05 mol % loading for gram-scale reactions.

An aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphtholate is described. The aldol reaction of trimethoxysilyl enol ether derived from cyclohexanone under anhydrous conditions predominantly afforded the anti-aldol adduct with moderate enantioselectivity, whereas the reaction under aqueous conditions predominantly resulted in the syn-adduct and the enantioselectivity of the syn-adduct was considerably improved. The best enantioselectivity was obtained in the reaction of trimethoxysilyl enol ether derived from 1-indanone with cyclohexanecarboxaldehyde (97% ee (syn)). This is the first example of an aldol reaction of trimethoxysilyl enol ether catalyzed by a chiral base.

The intramolecular Ru(II)-catalyzed radical addition of trichloroacetyl and 2,2-dichloro-4-hexenoyl pendant groups to a 1,3-dihydro-2-imidazolone moiety provides a perfectly stereocontrolled approach to the preparation of 1,2-diamines which contain contiguous multi-stereocenters. Typical examples for this approach are given by the chiral synthesis of vicinal-diaminocarboxylic acids, which are amino analogs of statine and MeBmt.

The preparation of a new class of "roofed" β-iminodisulfides from sterically congested, conformationally rigid chiral 2-thiazolidinones is described. A functional survey of palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate proved that symmetrical "roofed" β-iminodisulfides are efficient chiral ligands, showing enantioselectivity opposite that associated with chiral "roofed" β-iminothioether ligands.

Diastereoselectivity which is induced by the use of 2-imidazolidinone auxiliaries is greatly dependent on the N-substituents of the heterocycles, among which the bulky arenesulfonyl group is the moiety of choice. Reactions of this type afford an excellent level of diastereoselection in the methylation of N%-butyryl-2-imidazolidinones via the metal enolates. © 2000 Published by Elsevier Science Ltd.

The use of sterically congested C 2 -symmetrical bis(oxazoline) ligands with methylene and ethylene spacers between the oxazoline rings results in the reversal of the enantioselection for aldol reactions catalyzed by bis(oxazoline)–Cu(II) complexes.

An enantioselective borane-mediated deacylation of C 2 - symmetrical 1,3-diacetyl-2-imidazolidinethiones, catalyzed by oxazaborolidines derived in situ from an aminoalcohol 2 and borane, provides a promising process for highly effective kinetic resolution.

The intramolecular Ru(II)-catalyzed radical addition of the 2,2-dichloroacyl pendant group to the 2-oxazolone moiety followed by reductive dechlorination with (TMS)3SiH provides an effective tool for the formation of the chiral 2-amino alcohol synthon in a completely regio- and stereocontrolled manner. The prepared synthon is useful in the preparation of isomers of unusual amino hydroxy acids including the key component of bleomycins.

A reductive monodeacylation, catalyzed by oxazaborolidines derived from conformationally rigid chiral aminoalcohols providels a practical for the effective enantiodivergence of meso -1,3-diacetyl-2-imidazolidinones. This catalytic deacylation is successfully applied to the kinetic resolution of racemic 1-acetyl-2-oxazolidinones.

The enantioselective monodeacylation of meso -1,3-diacetyl-2-imidazolidinones, by treatmenmt with the lithium salts of sterically constrained N , N -dimethylaminoalcohol gives 1-acetyl-2-imidazolidinones in 89% ee. The latter compounds serve as good precursors for efficient chiral auxiliaries.

Synthetic potential of the simple heterocycle, 2-oxazolone, as a building block for 2-amino alcohols has been reviewed. Stereodefined introduction of easily replaceable groups to the olefinic moiety of the 2-oxazolone ring, followed by stereospecific and stepwise substitution, works well as a versatile strategy for the chiral synthesis of a wide variety of 2-amino alcohols of biological interest. Sterically constrained chiral 2-oxazolidinones and the derived 2-amino alcohols which are derived from cycloaddition of the 2-oxazolone to cyclic dienes such as anthracenes and cyclopentadiene have general use as excellent auxiliaries and ligands in asymmetric synthesis.

A new class of conformationally rigid 2-oxazolidinones with effectively bulky substituents, derived from the [4+2] cycloadduct of cyclopentadiene and 2-oxazolone, serve as extremely powerful chiral auxiliaries for asymmetric alkylations, Diels-Alder reactions and conjugate addition reactions.

The effectiveness of chiral phosphine oxide BINAPO as a catalyst for the enantioselective addition of allyltrichlorosilanes to aldehydes was demonstrated, wherein the combination of diisopropylethylamine and tetrabutylammonium iodide as additives is crucial for accelerating the catalytic cycle.

Topical adverse events caused by inhaled corticosteroids (ICS) are suspected to be more common in females. Although gargling or mouth washing after inhalation is recommended as the gold standard for preventing adverse events due to ICS, the preventive effects of this method have not been confirmed in real-world studies. This study aimed to examine the association between gargling or mouth washing and the incidence of topical adverse symptoms in males and females in daily practice.We analyzed a subpopulation of participants in the Drug Event Monitoring (DEM) project of the Japan Pharmaceutical Association. An anonymous survey was performed in February 2010, to assess the self-perception of topical adverse symptoms during ICS use by conducting interviews of pharmacists using structured questionnaires.A total of 412 males and 480 females were included. The patients used a dry-powder inhaler (DPI) (71.2%), pressurized meter-dose inhaler (pMDI) with (7.5%) or without (16.6%) a spacer or inhalation solution (4.7%) as the delivery device. Topical adverse symptoms occurring after previous prescriptions were reported by 41 (4.6%) subjects. The common symptoms were hoarseness, stomatitis and dry mouth (1.3%, 1.1% and 1.1%, respectively). In the multiple regression model, the presence of symptoms was found to be significantly associated with the absence of gargling or mouth washing after inhalation [adjusted odds ratio (OR): 3.75, 95% confidence interval (95%CI): 1.33-10.59, p = 0.012]. When stratified by gender, the absence of gargling or mouth washing was identified to be a risk factor in females only (OR: 4.32, 95%CI: 1.11-16.87, p = 0.035) and not in males (OR: 3.26, 95%CI: 0.65-16.33, p = 0.151). Furthermore, the association between the absence of gargling or mouth washing and the incidence of topical adverse symptoms was significant in the patients using DPI (OR: 4.85, 95%CI: 1.66-14.14, p = 0.004), but not in those using the other devices.In this study, the absence of gargling or mouth washing after ICS use was associated with topical adverse symptoms, especially in females. To achieve good adherence to treatment and improve the quality of life, female patients with asthma should strictly practice the gargling or mouth washing method.

Newly synthesized silver—carbene complexes are applied in the copper-catalyzed allylic arylation of cinnamyl bromide with Grignard reagent (II) to form predominantly the gamma-product (IV).

Diastereoselective ring-openings of meso -dicarboxylic anhydrides with the Li- and Zn-complexes generated in situ from sterically congested chiral N -sulfonylaminoalcohols proceed with a reversal of high stereoselection.

The differentiation between enantiotopic carbonyl groups of cyclic meso -dicarboxylic anhydrides has been attained with excellent diastereofacial selectivity with an isomer ratio above 99 : 1 by treatment with the lithium salts of sterically hindered chiral N -arylsulfonyl-2-aminoalcohols in the presence of hexamethylphosphoric triamide.

Both enantiomers of cis-4, 5-disubstituted 2-oxazolidinones, DHAOx, DMAOx, CPAOx and HMC0x, which are sterically congested and conformationally fixed by bicyclo [2.2.1] and [2.2.2] ring systems are newly prepared by the Diels-Alder reactions of 2-oxazolone with the cyclic dienes such as anthracenes and cyclopentadienes followed by optical resolution with MAC acid. These compounds, particularly DMAOx and HMCOx, serve well as the most powerful 2-oxazolidinones chiral auxiliaries reported so far for the asymmetric reactions such as alkylations, the Diels-Alder reactions, the Michael-type additions and aldol reactions.Sterically congested 2-aminoalcohol derivatives derived from the ring-opening of DHAOx and DMAOx are shown to be highly useful auxiliaries for enantioselective additions of diethylzinc to aldehydes and enantiodivergence of meso-dicarboxylic anhydrides.

Sterically congested [4+2]cycloadduct-based 2-oxazolidinones, (1 R , 2 R , 6 S , 7 S )-1, 7, 8, 9, 10, 10-hexamethyl- and (1 S , 2 R , 6 S , 7 S , 10 R )-1, 7, 8, 9, 10, 10-pentamethyl-3-oxa-5-azatricyclo[5.2.1.0 2,6 ]dec-8-en-4-ones and their enantiomers, derived from hexamethyl- and pentamethylcyclopentadienes and 2-oxazolone, serve as extremely powerful chiral auxiliaries in the asymmetric alkylations and Diels-Alder reaction.

A simple and inexpensive system comprised of H2O2-pyridine-FeCl3·6H2O for the catalysis of olefin epoxidation was established. Intriguingly, the reactivity of this system greatly depends on the amounts of pyridine. Various substrates, including aromatic and aliphatic olefins, were epoxidized by this simple system in moderate to excellent yields.

A simple and inexpensive system comprised of H(2)O(2)-pyridine-FeCl(3)·6H(2)O for the catalysis of olefin epoxidation was established. Intriguingly, the reactivity of this system greatly depends on the amounts of pyridine. Various substrates, including aromatic and aliphatic olefins, were epoxidized by this simple system in moderate to excellent yields.

The preparation of a new class of "roofed" β-iminodisulfides from sterically congested, conformationally rigid chiral 2-thiazolidinones is described. A functional survey of palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate proved that symmetrical "roofed" β-iminodisulfides are efficient chiral ligands, showing enantioselectivity opposite that associated with chiral "roofed" β-iminothioether ligands.

A promising method for the versatile synthesis of chiral 2-amino alcohols is provided by the enantioselective functionalization of the olefinic moiety of the simple heterocycle, 2-oxazolone, involving a stereodefined introduction of easily replaceable groups followed by stepwise substitution. Versatility of this method is shown in chiral synthesis of unusual hydroxy amino acids such as statine and hydroxyglutamic acid, which are the key components of bioactive peptides.

(4 S ,5 S )- and (4 R ,5 R )-1-Acyl-4,5-dimethoxy-2-imidazolidinone derivatives, which are readily accessible from simple 1,3-dihydro-2-imidazolone heterocycles, represent good candidates for a new class of chiral synthons for use in the preparation of optically active threo -diamines such as 2 S ,3 R - and 3 S ,4 S -diamino carboxylic acids.