The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Axial chirality in N,N‐dimethylaminopyridines as well as N,N‐dipropylaminopyridines bearing an internal carboxy group were evaluated based on their racemization barriers and circular dichroism spectra. The half‐life of racemization of N,N‐dipropylaminopyridine derivative 2 was estimated to be 19.7 days at 20°C. Its enantiomers isolated as optically active forms showed positive‐negative and negative‐positive...
α1‐Acid glycoprotein (AGP) interacts with lipid membranes as a peripheral membrane protein so as to decrease the drug‐binding capacity accompanying the β→α conformational change that is considered a protein‐mediated uptake mechanism for releasing drugs into membranes or cells. This study characterized the mechanism of interaction between AGP and lipid membranes by measuring the vacuum‐ultraviolet...
The chiroptical response in the form of vibrational circular dichroism (VCD) in the midinfrared region is found to be enhanced when a hydrogen of amino group of l‐tryptophan is substituted with acetyl, acryloyl, or maleyl group. The order of preference for VCD enhancement is found to be acryloyl > acetyl > maleyl group. The resulting experimental VCD spectra are also found to be satisfactorily...
Chiroptical materials have received much attention in diverse fields for applications such as displays, sensors, smart memory devices, and catalysis. Here, we develop a simple fabrication method for polymer films with tunable chiroptical properties using small amounts of self‐assembling fluorescent dye as an additive. Both the circular dichroism and circularly polarized luminescence signals of the...
Two new carotenoids, sapotexanthin 5,6‐epoxide and sapotexanthin 5,8‐epoxide, have been isolated from the ripe fruits of red mamey (Pouteria sapota). Sapotexanthin 5,6‐epoxide was also prepared by partial synthesis via epoxidation of sapotexanthin, and the (5R,6S) and (5S,6R) stereoisomers were identified by high‐performance liquid chromatography–electronic circular dichroism (HPLC‐ECD) analysis....
The solid‐state structure of LL/DD or LD/DL diphenylalanine diluted in KBr pellets is studied by infrared (IR) absorption and vibrational circular dichroism (VCD) spectroscopy. The structure depends on the absolute configuration of the residues. The natural LL diphenylalanine exists as a mixture of neutral and zwitterionic structures, depending on the humidity of the sample, while mostly the zwitterion...
The electronic circular dichroism (ECD) exciton chirality method is very useful for determining the absolute configuration (AC) of chiral compounds. In the ECD spectroscopy, the chromophore‐chromophore interaction, ie, exciton coupling, is very important. For example, Harada and Nakanishi first discovered in 1969 that chiral dibenzoates exhibit exciton split bisignate Cotton effects, from the sign...
The endophytic fungus Coniothyrium sp. was isolated from leaves of Quercus robur. Fermentation of this fungus on solid rice medium yielded two new furoic acid derivatives (1 and 2) and two additional known compounds. The structures of the new compounds were determined by extensive analysis of 1D and 2D nuclear magnetic resonance spectra as well as high‐resolution mass spectrometry data. Compound 1...
Aimé Cotton is known for his invention of circular dichroism spectroscopy. In 1913, he married Eugénie Feytis, a scientist who studied physics with Marie Curie. Following the Second World War, Eugénie Cotton was determined to advance the rights and standing of women, sure in the belief that doing so was necessary not only because it was just but also because a world with women in the forefront would...
An enantiomerically pure (R)‐2‐methylpyrrolidine‐based anilino squaraine crystallizes in two chiral polymorphs adopting a monoclinic C2 and an orthorhombic P212121 structure, respectively. By various thin‐film preparation techniques, a control of the polymorph formation is targeted. The local texture of the resulting textured thin films is connected to the corresponding optical properties. Special...
The circular dichroism spectra of a single chain of polyfluorene was predicted for a p‐twisted helix conformation and local planarized polymer sections in the presence and in the absence of thermal vibrations. Under thermal vibrations at 300 K, the planarized section of polyfluorene affords a red‐shifted positive dichroic band between 446 and 456 nm, preserving a degree of chirality. The S1 ← S0 excitation...
The eye lens is a biconvex structure composed of lens fibres, cells that lack of blood and nerve supply and of any organelle, allowing for a high concentration of water soluble proteins that determine the lens transparency and refractive index. The lens water soluble protein pool in mammals is composed of α‐, β‐, and γ‐crystallins, the latter being involved in calcium homeostasis and having structural...
Vibrational optical activity (VOA) consisting of infrared vibrational circular dichroism (VCD) and vibrational Raman optical activity (ROA) was predicted, discovered, and confirmed between 1971 and 1975. My path to VOA was mentored by three pioneers of chirality and vibrational spectroscopy: Professors Albert Moscowitz, Warner L. Peticolas, and Philip J. Stephens, and while they are no longer alive...
This manuscript describes predicted NMR shifts for the limonoid natural product xylogranatin F. The 1H and 13C NMR shifts of four diastereomers were evaluated by GIAO and hybrid DFT/parametric DU8+ methods. The results of the 1H and 13C NMR calculations for both the GIAO method and the DU8+ calculations suggest the revised structure that was recently reassigned by chemical synthesis. Furthermore,...
The modern β‐adrenergic agonists (β‐blockers) possess one or more than one chiral center in their structure. Two enantiomers exhibit distinct pharmacodynamic and pharmacokinetic behaviors. Current progress in drug designing has resulted in the ability to understand the role of chirality in modern therapeutics. Furthermore, with a greater understanding of the molecular structure of precise drug targets,...
Catechinopyranocyanidins A and B (cpcA and cpcB) are two purple pigments present in the seed‐coat of red adzuki bean, Vigna angularis, of which cpcA is the major pigment, containing two chiral carbons in the catechin part. Their absolute configurations were determined by comparison of their experimental and quantum chemical calculated electronic circular dichroisms (ECDs). These purple pigments are...
Two novel helical poly(phenylacetylene) derivatives containing chiral phenylethyl carbamate residues in the end of each side chain (PPA‐S and PPA‐R) were synthesized by polymerization of the corresponding phenylacetylene monomers using Rh(nbd)BPh4 as a catalyst in DMF. The enantioseparation properties of the polymers were evaluated as coated‐type chiral stationary phases (CSPs) for high‐performance...
R‐/S‐2‐(2‐hydroxypropanamido)‐5‐trifluoromethyl benzoic acid (R‐/S‐HFBA) is a novel COX inhibitor with remarkable anti‐inflammatory and antiplatelet aggregation activities, but no gastrointestinal toxicity. In our previous study, the different pharmacokinetic profiles of the two enantiomers in rats were observed after administration of R‐HFBA and S‐HFBA. Stereoselective protein binding of the two...
In this brief review on Koji Nakanishi's remarkable career in natural products chemistry, we have highlighted a number of his accomplishments that illustrate the broad diversity of his interests. These include the isolation, structure determination, and biological mechanism of action of many natural products including the triterpenoid pristimerin; the diterpenoid ginkgolides; insect and crustacean...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.