Absolute configuration of pterocidin,a potent inhibitor of tumor cell invasion from a marine-derived Streptomyces

During the course of screening natural products for the inhibitors of tumor cell invasion, pterocidin, a linear polyketide with a δ-lactone terminus, was rediscovered from a Streptomyces strain of a marine sediment-origin. A series of J-based configuration analyses and NOESY analysis, coupled with chemical derivatization and chiral anisotropy analysis, established the absolute stereochemistry of five asymmetric centers in this compound.     

Evaluation of influence of anisotropic diffusion near a wall in near-field fluorescence correlation spectroscopy of nanoparticles

Fluorescence correlation spectroscopy (FCS) of colloidal nanoparticles using a near-field fiber probe was numerically simulated. The near-wall dynamics was simulated by accounting for the anisotropic mobility of nanoparticles owing to hydrodynamic interaction with a wall (Stokes viscous force). By comparing the simulation results with theoretical model calculations, we found that the influence of anisotropic diffusion is insignificant in near-field FCS autocorrelation analysis.     

Vinyl Polymerization. 274. Polymerization of Acrylonitrile Initiated by the System Tetramethyl Tetrazene and Co(II) Chloride

Abstract

The binary system of tetramethyl tetrazene (TMT) and Co(II) chloride was used as initiator of acrylonitrile (AN) in dimethylformamide. The initial rate of polymerization (Rp) was found to be expressed by Rp = k[TMT]^0.62[Co(II) chloride]^0.57 [AN]^2.00

The polymerization was confirmed to proceed via a radical mechanism. The over-all activation energy for the polymerization was estimated as 15.1 kcal/mole. On the basis of these results and the product analysis of the reaction between the catalyst components in the absence of monomer, the initiation mechanism of the polymerization is discussed.     

Vinyl Polymerization. 439. Vinyl Polymerization Initiated by Poly(Ethylene Glycol] Diglycolic Acid or its Sodium Salt

Abstract

The polymerization of some kinds of vinyl monomer was found to occur in aqueous solutions of poly(ethylene glycol) diglycolic acid (PEG Acid) or sodium poly(ethylene glycol) diglycolate (PEG Acid Na) through radical mechanisms without any further initiator, as a so-called “uncatalyzed polymerization.” Although the initiating radical species for PEG Acid was determined to be the same as that for PEG Acid Na by means of the spin-trapping technique, the initiating ability of PEG Acid was higher than that of PEG Acid Na. These results are assumed to be attributable to the difference in the initiation mechanisms of the two systems and in the incorporating abilities of monomer into the hydrophobic areas formed by PEG Acid and PEG Acid Na.     

Intramolecular 1,3‐Dipolar Cycloaddition‐Mediated Stereoselective Synthesis of Disubstituted Cyclopentane: A Simple Model for the Cyclopentane Ring System of Polycyclic Oroidine Alkaloids

We present a diastereoselective synthesis of disubstituted cyclopentane 8 having a nitrogen‐containing quaternary carbon center, which is found in axinellamine A ( 5 ) and related compounds. During this work, we found that the 1,3‐dipolar cycloaddition product 24 immediately underwent intramolecular redox reaction at the newly formed morpholin‐2‐one moiety, thus affording disubstituted cyclopentane containing a tertiary amine ( 9 ) stereoselectively in good yield. The amine 9 was successfully converted into guanidine 31 , which corresponds to 8 , through iminium cation–enamine isomerization.     

Officinatrione: an unusual (17S)-17,18-seco-lupane skeleton,and four novel lupane-type triterpenoids from the roots of Taraxacum officinale

Novel 5 lupane-type of triterpenois, i.e., 3β-acetoxy-18α,19α-epoxylupan-21β-ol (1), 18α,19α-epoxy-21β-hydroxylupan-3-one (2), lup-18-ene-3,21-dione (3), lupa-18,21-dien-3β-yl acetate (4), and (17S)-17,18-seco-lup-19(21)-ene-3,18,22-trione (5), named officinatrione, as well as 16 known compounds from the roots of Taraxacum officinale collected in Takatsuki city, Osaka, Japan. Of the above compounds, 5 was the first lupane-type triterpene, of which the D-ring was open to form a nine-membered ring. Compounds 2 and 5 exhibited moderate cytotoxic activities against L1210 cell line (IC₅₀ 10.5 and 10.1 μM).     

Asymmetric α‐Hydroxylation of Tetralone‐Derived β‐Ketoesters by Using a Guanidine–Urea Bifunctional Organocatalyst in the Presence of Cumene Hydroperoxide

Highly enantioselective catalytic oxidation of 1‐tetralone‐derived β‐keto esters was achieved by using a guanidine–urea bifunctional organocatalyst in the presence of cumene hydroperoxide (CHP), a safe, commercially available oxidant. The α‐hydroxylation products were obtained in 99 % yield with up to 95 % enantiomeric excess (ee). The present oxidation was successfully applied to synthesize a key intermediate of the anti‐cancer agent daunorubicin ( 2 ).     

Development of continuous process enabling nanofibrillation of pulp and melt compounding

Microfibrillated cellulose (MFC), a mechanically fibrillated pulp mostly consisting of nanofibrils, is a very attractive material because of its high elastic modulus and strength. Although much research has been done on composites of MFC and polypropylene (PP), it has been difficult to produce such composites at an industrial level because of the difficulties in using MFC in such composites are not only connected to the polarity (that can be improved with compatibilizers), but also with the challenge to make a homogeneous blend of the components, and also the low temperature stability of cellulose that could cause problems during processing. We developed a new processing method which enables continuous microfibrillation of pulp and its melt compounding with PP. Never-dried kraft pulp and powdered PP were used as raw materials to obtain MFC by kneading via a twin-screw extruder. Scanning electron microscopy showed nano to submicron wide fibers entangled in the powdered PP. MFC did not aggregate during the melt compounding process, during which the water content was evaporated. Maleic anhydride polypropylene (MAPP) was used as a compatibilizer to reinforce interfacial adhesion between the polar hydroxyl groups of MFC and non-polar PP. We investigated the effect of MAPP content on the mechanical properties of the composite, which were drastically improved by MAPP addition. Needle-leaf unbleached kraft pulp (NUKP)-derived MFC composites had better mechanical properties than needle-leaf bleached kraft pulp (NBKP)-derived MFC composites. Injection molded NUKP-derived MFC composites had good mechanical and thermal properties. The tensile modulus of 50 wt% MFC composite was two times, and the tensile strength 1.5 times higher than that of neat PP. The heat distortion temperature of 50 wt% MFC content composite under 1.82 MPa flexural load was increased by 53 °C, from 69 to 122 °C. This newly developed continuous process using powder resin has the potential for application at an industrial level.