Guest-induced assembly of tetracarboxyl-cavitand and tetra(3-pyridyl)-cavitand into a heterodimeric capsule via hydrogen bonds and CH-halogen and/or CH-pi interaction: control of the orientation of the encapsulated guest

The guest- or solvent-induced assembly of a tetracarboxyl-cavitand 1 and a tetra(3-pyridyl)-cavitand 2 into a heterodimeric capsule 1.2 in a rim-to-rim fashion via four intermolecular CO(2)H.N hydrogen bonds has been investigated both in solution and in the solid state. In the (1)H NMR study, a 1:1 mixture of1a and 2a (R = (CH(2))(6)CH(3)) in CDCl(3) gave a mixture of various complicated aggregates, whereas this mixture in CDCl(2)CDCl(2) or p-xylene-d(10) exclusively produced the heterodimeric capsule 1a.2a. It was found that an appropriate 1,4-disubstituted-benzene is a suitable guest for inducing the exclusive formation of 1a.2a in CDCl(3). The ability of a guest to induce the formation of guest-encapsulating heterodimeric capsule, guest@(1a.2a), increased in the order p-ethyltoluene < 1-ethyl-4-methoxybenzene < or = 1-ethyl-4-iodobenzene < or = 1,4-dibromobenzene < 1-iodo-4-methoxybenzene < or= 1,4-dimethoxybenzene < or = 1,4-diiodobenzene. The (1)H NMR study revealed that a CH-halogen interaction between the inner protons of the methylene-bridge rims (-O-H(out)CH(in)-O-) of the 1a and 2a units and the halogen atoms of 1,4-dihalobenzenes and a CH-pi interaction between the methoxy protons of 1,4-dimethoxybenzene and the aromatic cavities of the 1a and 2a units play important roles in the formation of 1,4-dihalobenzene@(1a.2a) and 1,4-dimethoxybenzene@(1a.2a), respectively. A preliminary single-crystal X-ray diffraction analysis of guest@(1b.2b) (R = (CH(2))(2)Ph; guest = 1-iodo-4-methoxybenzene or p-xylene) confirmed that the guest encapsulated in 1b.2b is oriented with the long axis of the guest along the long axis of 1b.2b and that the iodo and the methoxy groups of the encapsulated 1-iodo-4-methoxybenzene are specifically oriented with respect to the cavities of the 2b and 1b units, respectively.     

Isolation and structure determination of a new marine toxin,neosurugatoxin, from the Japanese Ivory Shell, Babylonia japonica.

A new toxin, named neosurugatoxin, was isolated from the toxic Japanese Ivory Shell and its structure was determined by X-ray crystallographic analysis.     

Manganese(III)-based oxidation of 2,4-piperidinediones in the presence of alkenes

The manganese(III)-catalyzed aerobic oxidation of 2,4-piperidinediones was performed in the presence of alkenes at room temperature, producing 1-hydroxy-8-aza-2,3-dioxabicyclo[4.4.0]decan-7-ones in excellent yields. On the other hand, the 6-acetoxy-3-aza-7-oxabicyclo[4.3.0]nonan-2-ones were obtained by the oxidation of the 2,4-piperidinedione-3-carboxylates with manganese(III) acetate in the presence of alkenes at elevated temperature under an argon atmosphere. A similar oxidation using decarboxylated 2,4-piperidinediones produced the 2,3,6,7-tetrahydrofuro[3,2-c]pyridin-4(5H)-ones and/or 2,3,6,7-tetrahydrofuro[2,3-b]pyridin-4(5H)-ones in good yields. The structure determination and the decomposition reaction of the azabicyclic peroxides in acetic acid or acetic anhydride, and the reaction pathway were also described.     

Induction of a remarkable conformational change in a human telomeric sequence by the binding of naphthyridine dimer: inhibition of the elongation of a telomeric repeat by telomerase

The binding of a dimeric form of the 2-amino-1,8-naphthyridine derivative (naphthyridine dimer) to a human telomeric sequence, TTAGGG, was investigated by UV melting, CD spectra, and CSI-MS measurements. Both the 9-mer d(TTAGGGTTA) and the 15-mer d(TTAGGGTTAGGGTTA) showed apparent melting temperatures (T(m)) of 45.6 and 63.6 degrees C, respectively, in the presence of naphthyridine dimer (30 microM) in sodium cacodylate buffer (50 mM, pH 7.0) containing 100 mM NaCl. The CD spectra at 235 and 255 nm of the 9-mer increased in intensity accompanied with strong induced CDs at 285 and 340 nm upon complex formation with naphthyridine dimer. UV titration of the binding of naphthyridine dimer to the 9-mer at 320 nm showed a hypochromism of the spectra. A Scatchard plot of the data showed the presence of multiple binding sites with different association constants. Cold spray ionization mass spectrometry of the complex between naphthyridine dimer and the 9-mer clearly showed that one to three molecules of the ligand bound to the dimer duplex of the 9-mer. Telomeric repeat elongation assay showed that the binding of naphthyridine dimer to the telomeric sequence inhibits the elongation of the sequence by telomerase.     

Electrocatalytic Oxidation of Amines on a Mediator‐Modified Electrode by Electrochemical Copolymerization of Nitroxyl Radical Precursor Containing Pyrrole Side Chain and Bithiophene

This paper describes the electrocatalytic oxidation of amines on TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl)‐modified electrodes prepared by electrochemical copolymerization of TEMPO precursor containing pyrrole side chain and 2,2′‐bithiophene. The modified electrode exhibits electrocatalytic activity for the oxidation of primary and secondary amines. Cyclic voltammetric studies showed that the peak current of the cyclic voltammogram increased linearly with increasing concentration of amine in the sample solution.     

Dimesitylborylethynylated Arenes: Unique Electronic and Photophysical Properties Caused by Ethynediyl (C≡C) Spacers

Herein, we report the synthesis and electrochemical and photophysical properties of aromatic hydrocarbons having one or two dimesitylborylethynyl peripherals. The mono- ( 1 ) and diboryl compounds ( 2 ), readily prepared by nucleophilic substitution reaction, are fairly stable to air and moisture in the solid state. The inserted ethynediyl (C≡C) spacer cancels the steric hindrance between the bulky dimesitylboryl groups and aromatic rings, leading to effective π conjugation over the B−C≡C−Ar linkages, as revealed by cyclic voltammetry. Despite the small structural differences, the photophysical properties of the benzene, naphthalene, and anthracene derivatives are different. Virtually no emission was observed from the benzene derivatives, whereas the anthracene derivatives emitted with high quantum yields both in solution and in the solid state. Notably, the naphthalene derivatives showed aggregation-induced emission behavior. Unlike the common sterically congested triarylborane derivatives reported so far, the anthracene derivatives showed π–π*-type absorption and emission bands, which derive from efficient intramolecular orbital interactions between the boron centers and anthracene moieties, as supported by DFT calculations. As a result, the dimesitylborylethynyl substituents effectively lower the LUMO levels of the aromatic hydrocarbon parts, whereas the HOMO levels are almost unaffected, thereby leading to materials with controllable HOMO–LUMO gaps.     

Ultraviolet Photoelectron Spectra of Potassium Dosed Higher Fullerenes

Abstract

Ultraviolet photoelectron spectra of potassium dosed higher fullerenes are measured with a synchrotron radiation light source. Potassium dosing to higher fullerenes brings a new structure between the spectral onset of pristine fullerenes and the Fermi level. As the spectral edge of the new structure does not cross the Fermi level, potassium dosed higher fullerenes are not metallic but semiconductive. When the potassium is excessively dosed to the fullerenes, the lower binding energy structures above 5 eV become faint. In contrast to this phenomenon, four distinct structures appear between 5 and 14 eV.     

Saccharide Recognition by a Three-Arm-Shaped Host Having Preorganized Three-Dimensional Hydrogen-Bonding Sites

Generally, cage-shaped hosts for saccharides can bind strongly to guest molecules because of the three-dimensional preorganized hydrogen-bonding sites. However, the preparation of cage molecules is often difficult because of the low yield of the macrocyclization step. Here, we report a three-arm-shaped molecule possessing pyridine-acetylene-phenol units as a new kind of host having a preorganized three-dimensional hydrogen-bonding site. This three-arm-shaped host was readily prepared compared to a cage-shaped analogue. This host associated with lipophilic glycosides to form chiral complexes, and the association constants were sufficiently high as to be comparable to those of the cage-shaped analogue. Furthermore, this host extracted native monosaccharides into a lipophilic solvent.     

Reactions of Selenobenzophenones with Olefins

Reactions of selenobenzophenones with methyl propiolate afforded two types of cycloadducts regioselectively. The reaction with tetracyanoethylene gave selenophene derivatives. Mechanisms of these reactions were discussed.