A Silyliumylidene Cation Stabilized by an Amidinate Ligand and 4‐Dimethylaminopyridine

The synthesis and reactivity of a silyliumylidene cation stabilized by an amidinate ligand and 4‐dimethylaminopyridine (DMAP) are described. The reaction of the amidinate silicon(I) dimer [ L Si:]₂ ( 1 ; L =PhC(NtBu)₂) with one equivalent of N‐trimethylsilyl‐4‐dimethylaminopyridinium triflate [4‐NMe₂C₅H₄NSiMe₃]OTf and two equivalents of DMAP in THF afforded [ L Si(DMAP)]OTf ( 2 ). The ambiphilic character of 2 is demonstrated from its reactivity. Treatment of 2 with 1 in THF afforded the disilylenylsilylium triflate [ L′ ₂( L )Si]OTf ( 3 ; L′ = L Si:) with the displacement of DMAP. The reaction of 2 with [K{HB(iBu)₃}] and elemental sulfur in THF afforded the silylsilylene [ L SiSi(H){(NtBu)₂C(H)Ph}] ( 4 ) and the base‐stabilized silanethionium triflate [ L Si(S)DMAP]OTf ( 5 ), respectively. Compounds 2 , 3 , and 5 have been characterized by X‐ray crystallography.     

A one-pot tandem synthesis of various 1,2-disubstituted benzimidazoles

A facile method to synthesize various 1,2-disubstituted benzimidazoles is developed. It is suggested that formation of a Meisenheimer adduct between the substrate, amine, and solvent aids the N-arylation process. The generality of the protocol is demonstrated by the efficient reactions involving numerous substituents ranging from electron-withdrawing groups to electron-donating groups.     

Synthesis of Poly(ϵ-caprolactone) Grafted Poly(2-hydroxyethyl methacrylate) Functionalized Hydroxyapatite by RAFT and ROP

Poly(?-caprolactone) grafted poly(2-hydroxyethyl methacrylate) functionalized hydroxyapatite (HAP@PHEMA-g-PCL) nanocomposites were synthesized by the combination of reversible addition fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP). The RAFT agent was anchored on the surface of hydroxyapatite nanocrystals (HAPs) through the silane condensation process of 3-chloropropyltrimethoxysilane followed by reaction with potassium xanthogenate. Poly(2-hydroxyethyl methacrylate) (PHEMA) was covalently functionalized on the surface of HAPs by RAFT polymerization. Then, poly(?-caprolactone) (PCL) was grafted on HAPs by ROP based on the hydroxyl groups of PHEMA to afford HAP@PHEMA-g-PCL. The structure and composition of HAP@PHEMA-g-PCL nanocomposites were characterized by FT-IR, XRD, and TGA analyses. The morphology and formation of the polymer encapsulating HAPs were demonstrated from SEM and TEM images, while the ¹H MNR analysis of the cleaved PHEMA-g-PCL confirmed the grafting.     

Supramolecular Phthalocyanine Assemblies for Improved Photoacoustic Imaging and Photothermal Therapy

Phototheranostic nanoplatforms are of particular interest for cancer diagnosis and imaging‐guided therapy. Herein, we develop a supramolecular approach to fabricate a nanostructured phototheranostic agent through the direct self‐assembly of two water‐soluble phthalocyanine derivatives, PcS4 and PcN4. The nature of the molecular recognition between PcS4 and PcN4 facilitates the formation of nanostructure (PcS4‐PcN4) and consequently enables the fabrication of PcS4‐PcN4 with completely quenched fluorescence and reduced singlet oxygen generation, leading to the high photoacoustic and photothermal activity of PcS4‐PcN4. In vivo evaluations suggest that PcS4‐PcN4 could not only efficiently visualize a tumor with high contrast through whole‐body photoacoustic imaging but also enable excellent photothermal therapy for cancer.     

Indium trichloride mediated intramolecular Prins-type cyclization

[reaction: see text] Intramolecular Prins-type reactions of compounds having both functionalities of homoallyl alcohol and acetal moiety are described. The intramolecular Prins cyclizations were performed using indium trichloride in chloroform or 25% aqueous THF. Both 9-oxabicyclo[3.3.1]nonane and 3,9-dioxabicyclo[3.3.1]nonane compounds were successfully obtained in moderate yields.     

Synthesis of novel 2,6-disubstituted-3,4-dimethylidene tetrahydropyrans via Prins-type cyclization

Synthesis of novel substituted tetrahydropyrans with adjacent exo-methylene groups at the C3 and C4 positions via Prins-type cyclization has been described.     

Simplified method for concentration of mitochondrial membrane protein complexes

Extracting and concentrating mitochondrial protein complexes from gel strips after blue native PAGE (BN‐PAGE) can be daunting tasks using the traditional methods, such as electroelution, passive diffusion and centrifugal concentration. We present a simplified gel electrophoresis method to concentrate mitochondrial protein complexes with excellent recovery rate. Mitochondrial complex I present in a long gel strip from BN‐PAGE can be easily concentrated into a 0.8 cm gel strip when a second BN‐PAGE is performed with a Y‐shaped gel and the addition of 0.01% n‐dodecyl β‐D ‐maltoside and 0.001% SDS in the cathode buffer. Once completed, the concentrated protein complex in the gel strip is ready for SDS‐PAGE or proteomic studies.     

The first total synthesis of glycyrol

We report the first total synthesis of glycyrol. Glycyrol, isolated from Glycyrrhizae Radix, has a unique skeleton of a benzofuran coumarin. The key steps are Smiles rearrangement and selective introduction of prenyl and O-methyl groups. The first application of a novel precursor for Smiles rearrangement, 3-benzyloxy-substituted (diacetoxyiodo)benzene, showed the synthetic possibility for diverse precursors. The introduction of a benzyl protecting group was important because selective deprotection was hard due to the low solubility of intermediates.     

Effects of carbon nanotubes on dynamic mechanical property,thermal property,and crystal structure of poly(L‐lactic acid)

Effects of carbon nanotubes (CNT) on the dynamic mechanical property, thermal property, and crystal structure of poly(L ‐lactic acid) (PLLA) were investigated. Dynamic mechanical analysis (DMA) found that CNT via grafting modification with PLLA (CNT‐g‐PLLA) could result in effective reinforcing effects. Tan δ of DMA found that CNT‐g‐PLLA was compatible with the PLLA matrix, giving a single T_g of the composite with a higher CNT‐g‐PLLA loading giving a higher T_g of the composite. Wide angle X‐ray diffraction (WAXD) data demonstrated that CNT could assist the disorder‐to‐order (α′‐to‐α) transition in PLLA crystals but did not lead to a more compact chain packing of the crystal lattice in PLLA composites than in pure PLLA. The equilibrium melting temperature (T) obtained from Hoffman‐Weeks plots were found to increase with increasing CNT‐g‐PLLA content. Small angle X‐ray scattering data revealed that thicknesses of crystal layer and amorphous layer of PLLA both decreased with increasing CNT contents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 145–152, 2010     

Enzymatic transformation of platycosides and one‐step separation of platycodin D by high‐speed countercurrent chromatography

Platycosides, the saponins found in the roots of Platycodon grandiflorum (Platycodi Radix), are typically composed of oleanane triterpenes with two side chains. In platycosides, platycodin D, a glucose unit at C‐3, is a major component, which has several pharmacological activities. Because of the high demand for this compound, we attempted to enzymatically convert platycodin D₃ and platycoside E, having two and three glucose units at C‐3, respectively, into platycodin D. In this study, we tested the ability of several glycosidases to transform platycosides, or more specifically, the ability to transform platycoside E and platycodin D₃ into platycodin D. To obtain pure platycodin D on a preparative scale, high‐speed countercurrent chromatography with a solvent system of ethyl acetate/n‐butanol/water (1.2:1:2, v/v/v) was used for the separation of the enzymatically transformed product. Approximately 39.4 mg of platycodin D (99.8% purity) was obtained from 200 mg of the product in a one‐step separation. The results strongly support the advantage of enzymatic transformation of the platycosides for the efficient enrichment of platycodin D in the complicated extract of the medicinal plant.