Entrapment Efficiency of All-trans Retinoic Acid in Surfactant Vesicles

Spontaneous vesicles of dicetyl dimethyl ammonium chloride (DCDAC) and its mixture with sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) are observed respectively in ethanol-water mixed solvents, which have been demonstrated by negative-staining transmission electric microscope (TEM) and atomic force microscope (AFM). Ethanol can promote the vesicle formation, especially to pure DCDAC surfactant system. The entrapment efficiency of the vesicles to all-trans retinoic acid (ATRA) was measured by the first order derivative spectrophotometry method. The entrapment efficiency of ATRA reaches 22% in 0.5 ethanol volume ratio solution when the concentration of DCDAC is 2.5 × 10^?3 mol/L. In the same solvents, the entrapment efficiency could be as high as 62% in 1:9 (molar ratio) DCDAC/AOT mixtures when the total concentration of surfactants is 3.0 × 10^?3 mol/L.     

Acyclic diene metathesis polymerization of tailor-made monomers towards sequence-regulated vinyl copolymers

 Acyclic diene metathesis polymerization (ADMET) enables convenient transfer of sequential information of the designed monomers to the corresponding sequence-regulated copolymers. In this study, two structurally symmetric monomers, M1 and M2, were synthesized via atom transfer radical addition (ATRA) of diethyl meso-2,5-dibromohexanedioate with 1,5-hexadiene and 1,7-octadiene, respectively. Thus, sequenced segment of VB-EA-EA-VB (VB and EA represent vinyl bromide and ethyl acrylate, respectively) was incorporated into the ADMET diene monomers. ADMET polymerization of these two monomers with Grubbs first generation catalyst (Grubbs-I) was performed in CH₂Cl₂ at 40℃ for 5 days under nitrogen purge. Effects of catalyst amount, monomer concentration and methanol precipitation on the M_p and PDI of polymers were investigated by GPC, and the structures of the formed polymers were characterized by NMR. Our results indicate that using 3.0 mol% of Grubbs-I to monomer can afford polymers with high M_p. Moreover, selective precipitation in methanol enables complete removal of low molecular weight components from the crude products. Meanwhile, M2 exhibits higher ADMET polymerization reactivity than M1 due to its capability of suppressing negative neighboring group effect.     

Visible-light-promoted alkylation of unsaturated MIDA boronates using Ru(bpy)3Cl2 as the photoredox catalyst

The development of a visible light-mediated atom transfer radical addition (ATRA) of perfluoroalkyl iodides to ethynyl-, vinyl- and allyl-MIDA boronates using the reductive and oxidative quenching of [Ru(bpy)₃]Cl₂ is described. Using an operationally simple and mild protocol, the corresponding MIDA boronates containing perfluoroalkyl groups were obtained in moderate to high yields. The structures of three products were confirmed by single crystal X-ray diffraction studies.     

Immobilized copper catalyst for atom transfer radical addition and polymerization

A novel multidentate amine grafted on silica gel and magnetic microsphere was prepared. Its chemical structure was confirmed by C¹³ NMR, XPS and FTIR, and the nitrogen content was determined by elemental analysis. It was also used as a ligand for CuCl and successfully catalyzed the atom transfer radical addition of both carbon tetrachloride (CCl₄) to methyl methacrylate and methyl trichloroacetate to styrene, repeatedly. The conversion and purity of the product were determined through gas chromatography and ¹H NMR, respectively. The immobilized copper catalyst complex was also used in atom transfer radical polymerization of styrene initiated by 1,1,1,3‐tetrachloro‐3‐phenylpropane and methyl methacrylate initiated by methyl 2‐methyl‐2,4,4,4‐tetrachlorobutyrate, respectively. Although the polymerization took place successfully, it did not proceed in a controlled fashion. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation of Antiproliferative Terpene-Alkaloid Hybrids by Free Radical-Mediated Modification of ent-Kauranic Derivatives

A convenient strategy for molecular editing of available ent-kauranic natural scaffolds has been developed based on radical mediated C–C bond formation. Iodine atom transfer radical addition (ATRA) followed by rapid ionic elimination and radical azidoalkylation were investigated. Both reactions involve radical addition to the exo-methylenic double bond of the parent substrate. Easy transformations of the obtained adducts lead to extended diterpenes of broad structural diversity and artificial diterpene-alkaloid hybrids possessing lactam and pyrrolidine pharmacophores. The cytotoxicity of selected diterpenic derivatives was examined by in vitro testing on several tumor cell lines. The terpene-alkaloid hybrids containing N-heterocycles with unprecedented spiro-junction have shown relevant cytotoxicity and promising selectivity indexes. These results represent a solid basis for following research on the synthesis of such derivatives based on available natural product templates.     

Microemulsion of Tween‐80/n‐Butylalcohol/H2O System and Its Entrapment Efficiency of ATRA

Microemulsion of Tween‐80/n‐butylalcohol/H₂O system was prepared, and the microemulsion region as well as the influence of temperature and concentration of NaCl on the region were determined with ternary diagrams. The O/W, W/O, and B.C. regions were divided by the conductance method. The particle diameters of microemulsions with different NaCl concentrations or microemulsion‐enveloping all‐trans retinoic acid (ATRA) were measured with dynamic light scattering in O/W region. The release rate of ATRA was studied with dialysis a bag‐ultraviolet spectrophotometers and the anticancer activity of ATRA in microemulsion was investigated with cancer cells H446. Results showed that O/W microemulsion forms when water content is over 64% in the mixture. The influences of temperature and salinity on microemulsion region were very slight, and even the particle diameter decreased very little with increasing salt and ATRA concentrations. The microemulsion‐enveloping ATRA possessed eminent sustaining release efficiencys and the efficiency was further confirmed with the growth inhibitory effect test on human cancer cells H446.     

Structural studies of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine hetero‐scorpionate copper complexes

The structures of five compounds consisting of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine complexed with copper in both the Cu^I and Cu^II oxidation states are presented, namely chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(I) 0.18‐hydrate, [CuCl(C₁₅H₁₇N₃)]·0.18H₂O, (1), catena‐poly[[copper(I)‐μ₂‐(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ⁵N,N′,N′′:C²,C³] perchlorate acetonitrile monosolvate], {[Cu(C₁₅H₁₇N₃)]ClO₄·CH₃CN}_n, (2), dichlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) dichloromethane monosolvate, [CuCl₂(C₁₅H₁₇N₃)]·CH₂Cl₂, (3), chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) perchlorate, [CuCl(C₁₅H₁₇N₃)]ClO₄, (4), and di‐μ‐chlorido‐bis({(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II)) bis(tetraphenylborate), [Cu₂Cl₂(C₁₅H₁₇N₃)₂][(C₆H₅)₄B]₂, (5). Systematic variation of the anion from a coordinating chloride to a noncoordinating perchlorate for two Cu^I complexes results in either a discrete molecular species, as in (1), or a one‐dimensional chain structure, as in (2). In complex (1), there are two crystallographically independent molecules in the asymmetric unit. Complex (2) consists of the Cu^I atom coordinated by the amine and pyridyl N atoms of one ligand and by the vinyl moiety of another unit related by the crystallographic screw axis, yielding a one‐dimensional chain parallel to the crystallographic b axis. Three complexes with Cu^II show that varying the anion composition from two chlorides, to a chloride and a perchlorate to a chloride and a tetraphenylborate results in discrete molecular species, as in (3) and (4), or a bridged bis‐μ‐chlorido complex, as in (5). Complex (3) shows two strongly bound Cl atoms, while complex (4) has one strongly bound Cl atom and a weaker coordination by one perchlorate O atom. The large noncoordinating tetraphenylborate anion in complex (5) results in the core‐bridged Cu₂Cl₂ moiety.