Structures and Reactivities of -Alkenyl-Substituted Anilides: The "Magic" Methyl Effect on Alkene.

Methyl substitution at the double bond of -alkenyl anilides influences both the preferred conformation and the susceptibility to acidic hydrolysis. The R-substituted amide favors the trans conformation, whereas amides substituted at R or R favor the cis conformation. Substitution at the R and R positions increases the ratio of the trans conformer.

Synthesis and Conformational Analysis of -Aromatic Acetamides Bearing Thiophene: Effect of Intramolecular Chalcogen-Chalcogen Interaction on Amide Conformational Stability.

The conformations of aromatic amides bearing an -(2-thienyl) or -(3-thienyl) group were investigated in solution and in the crystal state. NMR spectral data indicate that the conformational preferences of these amides in solution are dependent not only on the relative π-electron densities of the -aromatic moieties, but also on the three-dimensional relationship between carbonyl oxygen and the -aromatic moieties. A comparison of the conformational preferences of -(2-thienyl)amides and -(3-thienyl)amides revealed that the -conformers of -(2-thienyl)acetamides are stabilized by 1,5-type intramolecular S···O═C interactions between amide carbonyl and thiophene sulfur.

Structure and Additive-free Transamidation of Planar -Cyano Amides.

Although transamidation of amides generally requires metals, additives, or harsh conditions, we present here a facile transamidation of -cyano amides with various amines at ambient temperature without any additive. -cyano amides preferred the trans conformation and have a reduced double bond character revealed by crystal analysis. The DFT study indicates that the transamidation reaction proceeds through the direct attack of amine on the amide carbonyl since the LUMO (or LUMO+1) is located at the carbonyl moiety.

Conformational Switch of Benzanilide Derivative Induced by Acid; Effect of Pentafluorobenzoyl Group.

Amide-based molecular switches had its limitation on structural diversities. In this work, we designed and synthesized a series of pentafluorobenzoyl-based benzanilide compounds. The conformational ratio of these compounds in solution was correlated linearly with Hammett's σ value of the substituent on the anilide ring, reflecting the repulsive interaction between the carbonyl group and the electron-rich aryl group.

Clostridium butyricum Modulates the Microbiome to Protect Intestinal Barrier Function in Mice with Antibiotic-Induced Dysbiosis.

Clostridium butyricum MIYAIRI 588 (CBM 588) is a probiotic bacterium that has previously been used to prevent antibiotic-associated diarrhea. However, the underlying mechanism by which CBM 588 protects the gut epithelial barrier remains unclear. Here, we show that CBM 588 increased the abundance of Bifidobacterium, Lactobacillus, and Lactococcus species in the gut microbiome and also enhanced the intestinal barrier function of mice with antibiotic-induced dysbiosis.

N-Ethynylation of Anilides Decreases the Double-Bond Character of Amide Bond while Retaining trans-Conformation and Planarity.

Activated amide bonds have been attracting intense attention; however, most of the studied moieties have twisted amide character. To add a new strategy to activate amide bonds while maintaining its planarity, we envisioned the introduction of an alkynyl group on the amide nitrogen to disrupt amide resonance by nN→C conjugation. In this context, the conformations and properties of N-ethynyl-substituted aromatic amides were investigated by DFT calculations, crystallography, and NMR spectroscopic analysis.

Spontaneous and Direct Transformation of N,O-Diaryl Carbamates into N,N'-Diarylureas.

We have discovered a spontaneous reaction of N,O-diaryl carbamates to afford symmetrical N,N'-diarylureas. Optimization of the conditions indicated that N,N-dimethylformamide (DMF) was the best solvent and triethylamine (EtN) was the best additive for this transformation. The reaction requires the presence of aryl groups on the nitrogen and oxygen atoms of carbamates.

Chemosynthetic homologues of Mycoplasma pneumoniae β-glycolipid antigens for the diagnosis of mycoplasma infectious diseases.

Mycoplasma pneumoniae expresses β-glycolipids (β-GGLs) in cytoplasmic membranes, which possess a unique β(1 → 6)-linked disaccharide epitope, which has high potential in biochemical and medicinal applications. In the present study, a series of β-GGLs homologues with different acyl chains (C12, C14, C16, and C18) were prepared from a common precursor. An ELISA assay using an anti-(β-GGLs) monoclonal antibody indicated that the synthetic homologues with long acyl chains had greater diagnostic potential in the order C18 > C16 > C14 > C12.

Remarkable functions of -3 hydroxy and phosphocholine groups in 1,2-diacyl--glycerolipids to induce clockwise (+)-helicity around the 1,2-diacyl moiety: Evidence from conformation analysis by H NMR spectroscopy.

Cell-membrane glycerolipids exhibit a common structural backbone of asymmetric 1,2-diacyl--glycerol bearing polar head groups in the -3 position. In this study, the possible effects of -3 head groups on the helical conformational property around the 1,2-diacyl moiety in the solution state were examined. H NMR Karplus relation studies were carried out using a series of 1,2-dipalmitoyl--glycerols bearing different -3 substituents (namely palmitoyl, benzyl, hydrogen, and phosphates).

Effect of Different Sampling Schedules on Results of Bioavailability and Bioequivalence Studies: Evaluation by Means of Monte Carlo Simulations.

Bioavailability and bioequivalence study is one of the most frequently performed investigations in clinical trials. Bioequivalence testing is based on the assumption that 2 drug products will be therapeutically equivalent when they are equivalent in the rate and extent to which the active drug ingredient or therapeutic moiety is absorbed and becomes available at the site of drug action. In recent years there has been a significant growth in published papers that use studies based on mathematical simulations to analyze pharmacokinetic and pharmacodynamic properties of drugs, including bioavailability and bioequivalence aspects.

A recyclable heavy fluorous tag carrying an allyl alcohol pendant group: design and evaluation toward applications in synthetic carbohydrate chemistry.

Toward applications in synthetic carbohydrate chemistry, we converted our previous acid-resistant heavy fluorous tag [(Rf)3C-CH2-OH, 1] to allyl alcohol derivatives [(Rf)3C-CH2-O-(CH2)n-CH=CH-CH2-OH, 3 (n=1) or 4 (n=3)] by means of olefin cross metathesis. They were then subjected to β-glycosylation reactions by using a series of glycosyl donors, including glycosyl bromide and trichloroacetimidates. The terminal OH group in 3 and 4 was found to be β-glycosylated in moderate yield when 2,3,4,6-tetra-O-benzoyl-D-galactosyl trichloroacetimidate was used as the glycosyl donor.

An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens.

Mycoplasma fermentans possesses unique α-glycolipid antigens (GGPL-I and GGPL-III) at the cytoplasm membrane, which carry a phosphocholine group at the sugar primary (6-OH) position. This paper describes a practical synthetic pathway to a GGPL-I homologue (C(16:0)) and its diastereomer, in which our one-pot α-glycosylation method was effectively applied. The synthetic GGPL-I isomers were characterized with (1)H NMR spectroscopy to determine the equilibrium among the three conformers (gg, gt, tg) at the acyclic glycerol moiety.

HPLC-UV determination of metformin in human plasma for application in pharmacokinetics and bioequivalence studies.

In this study, a simple, rapid and sensitive HPLC method with UV detection is described for determination of metformin in plasma samples from bioequivalence assays. Sample preparation was accomplished through protein precipitation with acetonitrile and chromatographic separation was performed on a reversed-phase phenyl column at 40 degrees C. Mobile phase consisted of a mixture of phosphate buffer and acetonitrile at flow rate of 1.

Depression of the apparent chiral recognition ability obtained in the host-guest complexation systems by electrospray and nano-electrospray ionization mass spectrometry.

Chiral recognition in the host-guest complexation systems of chiral crown ether hosts and amino ester guests was thoroughly examined using the electrospray ionization (ESI) mass spectrometry/enantiomer labeled (EL)-guest method. In this method, the mass spectra of a mixture of three components in a solution, a chiral host (H), an equal amount of an (S)-enantiomer guest labeled with deuterium atoms (G(S-dn)(+)) and an unlabeled (R)-enantiomer guest (G(R)+), were measured and the relative peak intensity value [I(H + G(R))(+) / I(H + G(S-dn))(+) = IRIS] of the host-guest complex ions, observed with an excess guest concentration, was taken to provide the chiral recognition ability of the host. In our earlier report (1996), we demonstrated that the apparent chiral recognition abilities using a mass spectrometer with a homemade ESI interface were depressed by about one tenth compared with the corresponding abilities obtained by fast-atom bombardment (FAB) MS.