Bis(5‐hydroxy‐2‐hydroxy­methyl‐4‐pyrone‐κ2O4,O5)bis(2‐hydroxy­methyl‐5‐oxido‐4‐pyrone‐κ2O4,O5)­calcium(II) tetrahydrate

In the title compound, [Ca(C₆H₅O₄)₂(C₆H₆O₄)₂]·4H₂O, which is a kojic acid–Ca²⁺ complex, the Ca atom is on a twofold axis and is octacoordinated by O atoms from four pyrone ligand mol­ecules. The hydroxyl and ketone O atoms of each ligand form a five‐membered chelate ring with the Ca atom. The crystal structure is stabilized by partial stacking and O—H?O hydrogen bonds.     

Smectic layer structure of ferroelectric liquid crystal formed between fine polymer fibres

This paper describes the alignment of ferroelectric liquid crystal (FLC) structures formed between aligned polymer fibres, where the FLC smectic layers are determined by polarising microscopy and X-ray diffraction. The FLC/polymer composite films were formed from a nematic phase FLC/monomer solution using a photopolymerisation-induced phase separation method. It was found that bending of the FLC smectic layers was induced in both the film plane and the cross-sectional plane at the phase transition from smectic A to chiral smectic C of the FLC material. The light transmittance properties of the composite film between crossed polarizers was analysed by light propagation simulation in several optical anisotropic media, based on the evaluated smectic layer model.     

Total synthesis of buergerinin F via effective construction of the asymmetric quaternary carbons using an enantioselective aldol reaction

An efficient method for the synthesis of (+)-buergerinin F is established via the enantioselective aldol reaction of a tetra-substituted ketene silyl acetal with crotonaldehyde, followed by intramolecular Wacker-type ketalization.     

The effective use of substituted benzoic anhydrides for the synthesis of carboxamides

Various carboxamides are synthesized from the corresponding carboxylic acids and amines with high product-selectivities using 2-methyl-6-nitrobenzoic or 2,4,6-trichlorobenzoic anhydride in the presence of 4-(dimethylamino)pyridine.     

Synthesis and pharmacology of 3,4-dihydro-3-oxo-1,4-benzoxazine-8-carboxamide derivatives, a new class of potent serotonin-3 (5-HT3) receptor antagonists.

A series of 3,4-dihydro-3-oxo-1,4-benzoxazine-8-carboxamide derivatives was synthesized and evaluated for serotonin-3 (5-HT3) receptor antagonistic activity assessed by their ability to antagonize the von Bezold-Jarish (BJ) effect in rats. Derivatives bearing 1-azabicyclo[2.2.2]oct-3-yl moiety as a basic function attached to the carboxamide at position 8 showed more potent antagonistic activity than those bearing the other three basic moieties. Structure-activity relationships of this series showed that methyl and chloro groups were more effective as substituents at positions 4 and 6, respectively. The representative compound 15 (Y-25130) in this series showed potent antagonistic activity on the BJ effect (ED50 = 1.3 micrograms/kg i.v.), high affinity for 5-HT3 receptor (Ki = 2.9 nM) and complete protection against cisplatin-induced emesis in dogs at a dose of 0.1 mg/kg i.v.     

Metal-assisted stabilization and probing of collagenous triple helices

Collagen model peptides that contain 2,2'-bipyridyl (bpy) ligands were designed and synthesized. The thermal stability of the collagenous triple helix was increased by forming an Fe(II)(bpy-peptide)(3) complex. The chirality of the metal center was shifted to form right-handed Delta-isomers induced by the supercoiling of the peptide moiety. Moreover, the refolding rate of the triple helix was increased in the presence of Fe(II). This metal-coordinating system possesses potential to be used to stabilize the triple-helical conformation as well as to probe the folding status of collagen model peptides.     

The effect of phenoxy oxygen atoms on extremely high extraction ability and less separation efficiency of trivalent rare earth elements with tetraphosphonic acid derivative of calix[4]arene

A cone confomational p-t-octylcalix[4]arene with four methylenephosphonic acids at the lower rim as well as its monomeric analog have been synthesized as a new extraction reagent to investigate the extraction behavior of the nine trivalent rare earth elements: Y, La, Pr, Nd, Sm, Eu, Gd, Ho and Er. The new calix[4]arene exhibited significantly higher extraction capacity than not only the monomeric derivative and the commercial extraction reagent, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate, but also the cone conformational calix[4]arene extractants employed in our previous work, composed of a tetrapropylenephosphonic acid with a longer spacer, a tetraphosphonic acid at the upper rim, and tetraacetic acid at the lower rim. A dependence on the pH was observed for the new extractant in the highly acidic region, and the extraction took place via a simple ion-exchange mechanism. Using slope analysis, the stoichiometries of tetrameric and monomeric extractants to rare earth metal ions were determined to be 2:1 and 3:1, respectively. Using the proposed extraction equations, extraction equilibrium constants and separation factors were estimated. The extremely high extraction ability and moderate separation efficiency were attributed to the chelating effect of the phosphonic acid and the phenoxy oxygen atom. The effect of the phenoxy oxygen atom on extraction ability and separation efficiency of calix[4]arene derivatives was found to be significant.     

Application of plug–plug technique to ACE experiments for discovery of peptides binding to a larger target protein: A model study of calmodulin‐binding fragments selected from a digested mixture of reduced BSA

To discover peptide ligands that bind to a target protein with a higher molecular mass, a concise screening methodology has been established, by applying a “plug–plug” technique to ACE experiments. Exploratory experiments using three mixed peptides, mastoparan‐X, β‐endorphin, and oxytocin, as candidates for calmodulin‐binding ligands, revealed that the technique not only reduces the consumption of the protein sample, but also increases the flexibility of the experimental conditions, by allowing the use of MS detection in the ACE experiments. With the plug–plug technique, the ACE–MS screening methodology successfully selected calmodulin‐binding peptides from a random library with diverse constituents, such as protease digests of BSA. Three peptides with K_d values between 8–147 μM for calmodulin were obtained from a Glu‐C endoprotease digest of reduced BSA, although the digest showed more than 70 peaks in its ACE–MS electropherogram. The method established here will be quite useful for the screening of peptide ligands, which have only low affinities due to their flexible chain structures but could potentially provide primary information for designing inhibitors against the target protein.