Weakly nucleophilic conjugate bases of superacids as powerful nucleophiles in vinylic bimolecular nucleophilic substitutions of simple β-alkylvinyl(aryl)-λ3-bromanes

We report herein, for the first time, the stereoselective synthesis of simple (E)-β-alkylvinyl(aryl)-λ(3)-bromanes via a boron-λ(3)-bromane exchange reaction and their unique bimolecular nucleophilic substitutions at the vinylic ipso carbon atom under mild conditions. Interestingly, even weakly nucleophilic anions such as conjugate bases of superacids (HBF(4), TfOH, Tf(2)CH(2), Tf(3)CH, Tf(2)NH, etc.) function as nucleophiles toward the vinyl-λ(3)-bromanes. For instance, the vinylic S(N)2 reaction of (E)-vinyl-λ(3)-bromanes with potassium bis(triflyl)methanide stereoselectively produced (Z)-vinyloxy oxosulfonium ylides with exclusive inversion of configuration via oxygen attack, while that with potassium bis(triflyl)imide afforded predominantly (Z)-vinyloxysulfoximines. In marked contrast, (E)-β-alkylvinyl-λ(3)-iodanes do not undergo the vinylic S(N)2 reaction with these conjugate bases of superacids. The differences between the nucleofugalities of aryl-λ(3)-iodanyl and aryl-λ(3)-bromanyl groups (the latter being greater) probably play a pivotal role in these unique reactions.     

2-Aryl-1,4-naphthoquinone-1-oxime methyl ethers: their cytotoxic activity

Preliminary examination for the structure-activity relationship of quinone monooxime derivatives on cytotoxicity against HeLa S3 cell and further trials using eight different cell lines suggested that 2-aryl-6,7-methylenedioxy-1,4-naphthoquinone-1-oxime methyl ethers, carrying 2-methoxy-4,5-methylenedioxyphenyl, 7-methoxy-2-methylbenzofuran-4-yl, and 2-methoxycarbonyl-3,4-dimethoxyphenyl as the 2-aryl substituent, were potential candidates for anti-cancer drugs.     

In situ synthesis and photoresponsive rupture of organosilica nanocapsules

This communication describes in situ synthesis of thiocyanato-functionalized organosilica nanocapsules by a sol-gel reaction using 3-thiocyanatopropyltriethoxysilane as a precursor. Moreover, the nanocapsules are photoresponsive and burst under light irradiation, resulting in release of the encapsulated drug or dye.     

Size-controlled long-circulating PICsome as a ruler to measure critical cut-off disposition size into normal and tumor tissues

Selective disposition of nanocarriers into target tissue is an essential issue in drug delivery. Critical size of nanocarriers (～150 nm) discriminating the permeability into normal and tumor tissues was determined by the use of size-tunable, polyion complex hollow vesicles (PICsome) as a ruler.     

Electron energy distribution of a current-free double layer: Druyvesteyn theory and experiments

Electron energy distributions upstream of a current-free double layer (CFDL) contained in a low-collisional plasma are modeled and compared with experimental results. The experimentally observed electron energy probability functions (EEPFs) with a depleted tail above the energy corresponding to the potential drop of the CFDL can be well approximated by a Druyvesteyn distribution function. Theoretical effective electron temperatures for the Druyvesteyn distribution are in good agreement with the values obtained from the experimental EEPFs over the range of pressure where the CFDL is observed.     

Donor–Acceptor Oligoimides for Application in High‐Performance Electrical Memory Devices

Two new oligoimides, OI(APAP-6FDA) and OI(APAN-6FDA) , which consisted of electron‐donating N‐(4‐aminophenyl)‐N‐phenyl‐1‐aminopyrene ( APAP ) or N‐(4‐aminophenyl)‐N‐phenyl‐1‐aminonaphthalene ( APAN ) moieties and electron‐accepting 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride ( 6FDA ) moieties, were designed and synthesized for application in electrical memory devices. Such devices, with the indium tin oxide (ITO)/oligoimide/Al configuration, showed memory characteristics, from high‐conductance Ohmic current flow to negative differential resistance (NDR), with corresponding film thicknesses of 38 and 48 nm, respectively. The 48 nm oligoimide film device exhibited NDR electrical behavior, which resulted from the diffusion of Al atoms into the oligoimide layer. On further increasing the film thickness to 85 nm, the OI(APAP-6FDA) film device showed a reproducible nonvolatile “write once read many” (WORM) property with a high ON/OFF current ratio (more than ×10⁴). On the other hand, the device that was based on the 85 nm OI(APAN-6FDA) film exhibited a volatile static random access memory (SRAM) property. The longer conjugation length of the pyrene unit compared to that of a naphthalene unit was considered to be responsible for the different memory characteristics between these two oligoimides. These experimental results suggested that tunable switching behavior could be achieved through an appropriate design of the donor–acceptor oligoimide structure and controllable thickness of the active memory layer.     

Fine‐Tuning of Charge‐Conversion Polymer Structure for Efficient Endosomal Escape of siRNA‐Loaded Calcium Phosphate Hybrid Micelles

For efficient delivery of siRNA into the cytoplasm, a smart block copolymer of poly(ethylene glycol) and charge‐conversion polymer (PEG‐CCP) is developed by introducing 2‐propionic‐3‐methylmaleic (PMM) amide as an anionic protective group into side chains of an endosome‐disrupting cationic polyaspartamide derivative. The PMM amide moiety is highly susceptible to acid hydrolysis, generating the parent cationic polyaspartamide derivative at endosomal acidic pH 5.5 more rapidly than a previously synthesized cis‐aconitic (ACO) amide control. The PMM‐based polymer is successfully integrated into a calcium phosphate (CaP) nanoparticle with siRNA, constructing PEGylated hybrid micelles (PMM micelles) having a sub‐100 nm size at extracellular neutral pH 7.4. Ultimately, PMM micelles achieve the significantly higher gene silencing efficiency in cultured cancer cells, compared to ACO control micelles, probably due to the efficient endosomal escape of the PMM micelles. Thus, it is demonstrated that fine‐tuning of acid‐labile structures in CCP improves the delivery performance of siRNA‐loaded nanocarriers.

     

Algebraic independence results for the values of certain Mahler functions and their application to infinite products

In this paper we establish algebraic independence criteria for the values at an algebraic point of Mahler functions each of which satisfies either a multiplicative type of functional equation or an additive one. As application we construct, using a linear recurrence sequence, an entire function defined by an infinite product such that its values as well as its all successive derivatives at algebraic points other than its zeroes are algebraically independent. Zeroes of such an entire function form a subsequence of the linear recurrence sequence. We prove the algebraic independency by reducing those values at algebraic points to those of Mahler functions.     

Reactivity of Hydroxy‐ and Aquo(hydroxy)‐λ3‐iodane–Crown Ether Complexes

We have designed a series of hydroxy(aryl)‐λ³‐iodane–[18]crown‐6 complexes, prepared from the corresponding iodosylbenzene derivatives and superacids in the presence of [18]crown‐6, and have investigated their reactivities in aqueous media. These activated iodosylbenzene monomers are all non‐hygroscopic shelf‐storable reagents, but they maintain high oxidizing ability in water. The complexes are effective for the oxidation of phenols, sulfides, olefins, silyl enol ethers, and alkyl(trifluoro)borates under mild conditions. Furthermore, hydroxy‐λ³‐iodane–[18]crown‐6 complexes serve as efficient progenitors for the synthesis of diaryl‐, vinyl‐, and alkynyl‐λ³‐iodanes in water. Other less polar organic solvents, such as methanol, acetonitrile, and dichloromethane, are also usable in some cases.