Carbonyl methylenation of easily enolizable ketones

An organometallic reagent prepared from CH₂I₂, Zn, and TiCl₄ is effective for methylenation of the title ketones.     

Determination of Low-Level Ethylenediaminetetraacetic Acid in Water Samples by Ion Chromatography with Ultraviolet Detection

A convenient and sensitive ion chromatographic (IC) method for the analysis of ethylenediaminetetraacetic acid (EDTA) in water samples was proposed. Using a fast reversible reaction of free EDTA and metal–EDTA complexes into Fe(III)–EDTA complex in the presence of Fe(III) ions, sample solutions were applied to an ion-exchange column using a mobile phase (pH 2.3), which was composed of 100 μM Fe(III) chloride and 5 mM methanesulfonic acid. The addition of Fe(III) solution (100 μL) containing 10 mM Fe(III) chloride and 0.5 M methanesulfonic acid to the sample solution (10 mL) permitted the injection of a large volume (400 μL) of sample, which allowed for greater sensitivity. The proposed IC method gave a highly linear (r ² > 0.999) calibration curve ranging 0.005–1.0 μM EDTA and had a limit of detection of 1.5 nM. High repeatability (RSD < 2.1%) and recoveries (88–108%) were also obtained. With this method, total EDTA level in raw and drinking waters were analyzed successfully.     

Improved separation of alpha chains of collagen type I, type III, and type V by noninterrupted electrophoresis using thioglycolic acid as a negatively charged reducer

Improved separation of alpha chains of collagen type I (alpha 1 [I]2 alpha 2[I]), type III(alpha 1[III]3), and type V (alpha 1[V]alpha 3[V])was achieved by noninterrupted sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a negatively charged reducer, thioglycolic acid. The thioglycolic acid, added to the running buffer of the cathodic reservoir, in the middle of electrophoresis quickly migrated in the gel anode, reducing interchain disulfide linkages in collagen type III and dissociating it into its alpha chain monomer, alpha 1[III], without an interruption of electrophoresis. The alpha chain, alpha 1[III], migrated more slowly than the alpha 1 [I] and alpha 2[I] chains of collagen type I, resulting in an excellent separation of alpha 1[III] from alpha 1[I]. The mobility of alpha 1[III] could be controlled by varying the time of thioglycolic acid addition to the running buffer. This enabled us not only to separate alpha 1[III] from alpha 1[I] and alpha 1[V], but also to precisely quantitate these alpha chains, even at low protein loading of mixed samples.     

Convergent syntheses of polycyclic ethers. Illustrations of the utility of acetal-linked intermediates

One of the most characteristic and spectacular class of compounds isolated from marine sources is the polycyclic ethers. Following the initial report of the structural determination of brevetoxin B, a variety of novel polycyclic ethers have begun to surface. These natural products include ciguatoxins, gambierol, gambieric acids, yessotoxins and gymnocins, each of which exhibit distinct biological properties such as cytotoxicity and neurotoxicity, as well as antiviral and antifungal activities. Because of these intriguing biological activities and their complex molecular architecture, the total synthesis of these compounds has been pursued by many laboratories over two decades. In particular, the development of novel convergent strategies to assemble the structural fragments is crucial for the successful construction of these nano-scale molecules. This Perspective will focus on a recent convergent methodology using an acetal-linkage as a key motif. Application of this methodology culminated in the total syntheses of gambierol and ciguatoxin CTX3C.     

Electron spin resonance study of polymerization of butadiene with tris(acetylacetonato)titanium and triethylaluminum

ESR spectra of homogeneous catalyst derived from tris(acetylacetonato)titanium(III) and triethylaluminum were observed at several temperatures from ?78°C, to +25°C, at molar ratios of aluminum to titanium of 1–108. At ?78°C, this catalyst yields a violet complex which shows an ESR signal with a g value of 1.959 and is associated with the first intermediate. At ?40°C to ?30°C, this signal decreases, and two signals with g values of 1.947 and 1.960 are observed. The latter two signals diminish at ?5°C to +10°C, while two kinds of new signals with g values of 1.965 and 1.969 appear overlapping each other. The structures of the species corresponding to these five signals are discussed on the basis of the ESR spectra, the intensity change, and the unpaired spin distribution. A new signal with a g value of 1.978 is found in the presence of butadiene at 25°C at Al/Ti > 8 and is assigned to a growing end of polybutadiene with this catalyst. The polymer yield increases remarkedly at Al/Ti molar ratios greater than 10. The microstructure of the resulting polymer consists almost completely of 1,2 units. The structure of the growing end is proposed to be a titanium (III) species containing two 1-substituted allyl groups, by comparison with the structure ascribed to the growing end of polybutadiene with n-butyl titanate-triethylaluminum catalyst.     

Determination of the specific interaction of disubstituted aromatic compounds on hydrous zirconium oxide-loaded porous polymer resin

Summary A porous polymer resin loaded with hydrous zirconium oxide (Zr-gel) was evaluated as a stationary phase for the liquid chromatographic separation of disubstituted aromatic compounds. The prepared Zr-gel was used to separate disubstituted phenols andortho-substituted benzoic acid derivatives in reversed-phase mode. The retention time of catechol was greater than those of other disubstituted phenols; this implies that the Zr-gel has specificity for the phenolic hydroxyl group. The retention behavior ofortho-substituted benzoic acid derivatives on the Zr-gel was also evaluated in reversedphase mode using buffer. Phthalic acid was specifically retained in the vicinity of pH 6.0, which has been regarded as the equal adsorbic point. Similar behavior was also observed for salicylic acid, although the retention time of salicylic acid was less than that of phthalic acid. It seems that the specific retention behavior of hydrous zirconium oxide is a result of complexation with ligands such as hydroxyl and carboxyl groups. The results of this study have revealed that the retention mechanism of hydrous zirconium oxide is a combination of ion exchange and interaction based on complexation with ligands.     

Diversity-oriented synthesis of tamoxifen-type tetrasubstituted olefins

A general synthetic scheme for tamoxifen-type tetrasubstituted olefins based on the novel Cu-catalyzed carbomagnesation across alkynyl(2-pyridyl)silane has been developed. A wide array of electronically and structurally diverse tetrasubstituted olefins can be prepared in a regiocontrolled, stereocontrolled, and diversity-oriented manner. Noteworthy features are that (i) the three aryl groups, which are believed to be important (essential) for anti-estrogenic activity, can be varied at will because they all stem from readily available aryl iodides, and (ii) any stereo- and regioisomers can, in principle, be prepared by simply changing the applying order of aryl iodides into the sequence.     

Rheology of polystyrene solutions around the coil overlapping concentration: A phenomenological description of stresses in simple shear flow

Linear viscoelasticity behavior is described with the sum of two terms for polystyrene solutions in tricresyl phosphate around the coil overlapping concentration (K. Osaki, T. Inoue, & T. Uematsu, J Polym Sci Part B: Polym Phys 2001, 39, 211). One is a Rouse–Zimm (RZ) term represented by the Zimm theory with arbitrarily chosen values of the hydrodynamic interaction parameter and the longest relaxation time (τ_RZ). The other (the L term) consists of a relaxation mode with a single relaxation time (τ_L > τ_RZ) and a high‐frequency limiting modulus proportional to the square of the concentration. In this study, we describe the viscosity (η) and first normal stress coefficient (Ψ₁) in steady shear with simple formulas. The stress due to the L term is assumed to be given by a Kaye, Bernstein, Kearsley, and Zapas (K‐BKZ) equation with the damping function h(γ) = (1 + 0.2γ²)^?1/2, where γ is the magnitude of shear. Contributions to η and Ψ₁ from the RZ term are derived from the RZ model, in which the relaxation time in steady flow is given by τ_st = τ + (τ_RZ ? τ)/(1 + 0.35τ_RZ γ˙) instead of τ_RZ. Here, γ˙ is the rate of shear, and τ is the τ_RZ value at the infinite dilution limit. η and Ψ₁ at various concentrations for two polystyrene samples (with molecular weights of 2890 and 8420 kg mol^?1) are well described with parameters derived from dynamic viscoelasticity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1038–1045, 2002     

Studies on sustained-release suppositories. III. Rectal absorption of morphine in rabbits and prolongation of its absorption by alginic acid addition

Rectal absorption of morphine from various kinds of suppository bases was investigated. The extent of bioavailability of morphine by rectal administration varied with the bases used (30.5-97.5%), but every value was higher than that in the case of oral administration (13.5%). Witepsol bases were preferable to macrogol base for the rectal absorption of morphine. In particular, Witepsol S-55 or W-35 gave a higher plasma peak level than H-15 or E-75, whereas the difference in the mean residence times obtained from these bases could not be regarded as significant. Sustained-release suppositories of morphine could be prepared simply by mixing alginic acid (Alg) with morphine in a suppository base. Further, prolonged rectal absorption could be obtained by using these sustained-release suppositories, and the absorption rate was controlled by the amount of Alg added. It seems likely that the sustained release was due to the binding of morphine to Alg from the results of partition coefficient and binding ratio measurements in aqueous solution. The rapid initial absorption and the subsequent prolonged absorption of morphine simultaneously obtained from the morphine-Alg suppository may be useful in the clinical context.     

Preparation and properties of polyamides and polymides containing bibenzyl,stilbene, and tolan structures

Polyisophthalamides and polyterephthalamides were prepared by the solution polycondensation of the corresponding diacyl chlorides with 4,4′-diaminobibenzyl, trans-4,4′-diaminostilbene, and 4,4′-diaminotolan in N,N-dimethylacetamide (DMAc). Polypyromellitimides were synthesized in two steps by the ring-opening polyaddition of pyromellitic dianhydride with the aromatic diamines in DMAc, followed by thermal cyclodehydration. The amorphous polyisophthalamides were soluble in some amide solvents containing lithium chloride, while the polyterephthalamides having fair degree of crystallinity were insoluble in these solvents. The thermal stability of these aromatic polymers decreased in the order of the tolan-containing polymers > the stilbene-containing polymers > the bibenzyl-containing polymers, both in air and under nitrogen.