Diphenyl Ether Moiety Research Articles

Alignment of a nematic liquid crystal induced by anisotropic photo-oxidation of photosensitive polyimide films

The alignment of a nematic liquid crystal (LC) could be induced by three polyimide (PI) films exposed to linearly polarized ultraviolet (UV) light of long wavelength (366 nm). The alignment could also be modified by changing the direction of polarization of the linearly polarized light (LPL). Infrared (IR) and UV-visible spectroscopy indicated that among the three PI films the PI with a benzophenone moiety and the PI with a diphenyl methane moiety were sensitive to UV radiation and susceptible to remarkable ablation after irradiation with LPL in air. Polarized UV-visible spectroscopy indicated that dichroism of the PI films was caused by LPL and altered by changing the polarization of the LPL. Furthermore, the PI films irradiated under vacuum showed little reduction in intensity of IR bands, which is in sharp contrast to the marked decreases in samples irradiated in atmospheres containing oxygen. This proves that oxygen is necessary to the ablative process of the PI films. Our results indicate that the mechanism of LC alignment on the photosensitive PI films is photoinduced anisotropic oxidative ablation of the PI films. In contrast, the PI film with a diphenyl ether moiety was quite stable under similar irradiation conditions even though the irradiated PI film could also induce alignment of the LC molecules.

Transient Absorption Spectra of Photoconductive Polyimides and Their Model Compound by Picosecond Pulse Radiolysis

Transient absorption spectra of an aromatic polyimide, PI(PMDA/ODA), and a polyimide with an alicyclic diamine, PI(PMDA/DCHM), were determined in order to investigate the main active species in the photoconductivity of the polyimide films by picosecond pulse radiolysis method. A model compound, N,N‘-di-n-butylpyromellitic diimide (DBPMDI), was utilized to investigate the active species of pyromellitic imide moieties in solutions of dichloromethane (DCM) and tetrahydrofuran (THF). In the aromatic polyimide film, the radical anions of the electron-accepting pyromellitic imide moieties at 660 and 720 nm and the radical cation of diphenyl ether moieties at 550 nm were determined by electron transfer from the aromatic ring to imide moieties in the polymer backbone. In the polyimide film with the alicyclic diamine, by utilizing the model system, only the radical anions of pyromellitic imide moieties could be assumed at 660 and 720 nm as the active species in the photoconductivity of the polyimide film. These ac...

Thermotropic polyamides containing the benzophenone unit

AbstractThe synthesis and structure‐property relationship of fully aromatic homo‐ and copolyamides are described. They all contain the 3,4′‐substituted benzophenone and diphenyl ether moiety in the main chain. The synthesis of the polyamides was performed at low temperatures with silylated aromatic diamines and aromatic acid chlorides. The polymers possess good solubility in dipolar aprotic solvents. They display thermotropic liquid crystalline properties. Based on results obtained by means of polarization microscopy, X‐ray scattering, and molecular dynamics simulation a rather unusual structure is proposed. It consists of a superlattice composed alternatingly of smectic B layers and amorphous layers. The formation of smectic B layers is untypical for main‐chain LC polymers without aliphatic spacers.

Studies on the Constituents of Aceraceae Plants. XIII. Diarylheptanoids and Other Phenolics from Acer nikoense.

From a mixture of the bark and twigs of Acer nikoense MAXIM. (Aceraceae), nine compounds (1-9) were newly isolated. Compound 1 was identical with acerogenin E, and compounds 8 and 9 were β-orcinol derivatives. Acerogenin K (2), a new diarylheptanoid of the cyclic diphenyl type, yielded acerogenin E on oxidation. Acerogenins F (3) through L (7) are new diarylheptanoids of the cyclic biphenyl ether type, whose skeletons and substituents of the diphenyl ether moieties are the same as those of acerogenin A. Their structures were elucidated on the basis of chemical and spectroscopic evidence.

Synthesis and Herbicidal Activity of Cyperin

Cyperin is a phytotoxic diphenyl ether natural product. Total synthesis of cyperin has been achieved and its herbicidal activity evaluated. The synthesis is highlighted by an Ullmann coupling to construct the diphenyl ether moiety contained within cyperin. It was found that cyperin inhibited root growth of Cyperus rotundus grown on agar; however, root growth of Cyperus grown in soil was unaffected. Cyperin also inhibited growth of Arabidopsis thaliana end Agrostis palustris grown in agar. The mode of action of cyperin is different from that of commercial diphenyl ether herbicides that inhibit protoporphyrinogen oxidase.

Molecular modelling of host-guest interactions for mass sensitive chemical sensors

Paracyclophanes are effective coatings for mass sensitive chemical sensors. The enzyme analogue recognition can preferably be used to detect aromatic and halogenated hydrocarbons. Molecular modelling by the MM3 force field allows the prediction of an efficient analyte inclusion. Besides the necessary steric complementarity it could be shown that the interaction between the methyl groups of aromatic guests (e.g. toluene) and the aromatic walls of the host is essential for hostguest complexation. These phenomena get more pronounced if bicyclic cyclophanes are applied and these sensitive materials enable the detection of only a few ppm of toluene with SAW devices. Furtheron, the electron-rich diphenylether moieties of these hosts guarantee interactions with electron-deficiency analytes such as chlorinated hydrocarbons with a selectivity superior to that of the monocyclic materials.

Degradation of aromatic polymers—III. Crosslinking and chain scission during photodegradation of polysulphones

Bisphenol A polysulphone (PSF) and polyethersulphone (PESF) were photodegraded homogeneously at room temperature in an inert and a normal atmosphere. The average molecular weights and the molecular weight distributions of degraded samples were measured by means of GPC to evaluate the quantum yields of chain scission and crosslinking. Simultaneous crosslinking and chain scission occur in the photodegradation of PSF and PESF. The ratio of the chain scission rate to the crosslinking rate was found to be 4.5 for PSF and 6.0 for PESF in the early stage of degradation. Quantum yields of crosslinking and chain scission were found to be of the order of 10 −4 for PSF as well as PESF and they are not greatly affected by the atmosphere during irradiation. It was also found that deceleration of reaction occurs in the later stages of degradation of both PSF and PESF. Photodegradation through addition to the benzene rings and H-abstraction by phenyl radicals formed by CS cleavage at diphenylsulphone moieties is proposed. The formation of phenol moieties by the photorearrangement of diphenylether moieties was revealed and related with the deceleration of reactions in the later stages of photodegradation of polysulphones, on the basis of i.r. analysis.

Oxidative irradiation effects on several aromatic polyimides

Radiation deterioration in mechanical properties under the oxidative condition (γ-rays under oxygen pressure) of polypyromellitimide (I), two copolymer type polyimides (II, III), two biphenyl tetracarboxylic acid anhydride type polyimides (IV, V) and polyetherimide (VI) was studied and was compared with the deterioration under the non-oxidative condition (high dose rate electron beam). Polyimides I–V showed a high resistance to radiation over 50 MGy under non-oxidative irradiation. Under oxidative irradiation they deteriorated at doses which were only 1 5 to 1 10 as strong as those used for non-oxidative irradiation. Measurements of the i.r. spectra and dielectric properties of polyimide I showed that the deterioration of mechanical properties under non-oxidative irradiation was mainly brought about by crosslinking. Under oxidative irradiation, mechanical properties were degraded by chain scission on imide and diphenyl ether moieties.

Synthesis of thyroid hormone analogues. Part 1. Preparation of 3′heteroarylmethyl-3,5-di-iodo-L-thyronines via phenol–dinitrophenol condensation and relationships between structure and selective thyromimetic activity

3′-Heteroarylmethyl analogues (1)–(8) of the natural thyroid hormone 3,3′,5-tri-iodo-L-thyronine (T3) were synthesized as potential selective (cardiac-sparing) thyromimetics. The diphenyl ether moiety was constructed by condensation of 3-substituted 4-methoxyphenols with a 3,5-dinitro-L-tyrosine derivative. Synthesis of the key phenols (28)–(32) required the in situ preparation, at low temperatures, of the novel metallated species 2-lithio-5-methoxypyridine (14), 5-lithio-2-methoxypyrimidine (15), 5-lithio-2-methylpyridine (16), 5-bromo-4-lithio-2-methoxypyridine (18), and 2,6-difluoro-3-lithiopyridine (19), followed by reaction with the benzaldehyde (20). Alternative routes to the pyridazinone (36) and thiazolone (37) phenols were developed from the benzyl bromide (33). Structure-activity relationships indicate that selective thyromimetic activity is associated with 2-oxyheteroaren-5-ylmethyl 3′-substitution, as found in the pyridone (1), pyridazinone (2), hydroxypyridine (4) and thiazolone (8). The location of the oxy substituent in the heterocycle is critical for both hormonal activity and for binding to the T3 receptor.

The structure of an antibiotic, dityromycin

Dityromycin is a peptide antibiotic isolated from the culture broth of the soil microorganism, Streptomyces sp. strain No. AM-2504, showing activities against Bacillus , Corynebacterium , and Clostridium . Dityromycin was clarified to be composed of N-MeVal, Pro, Val, Phenylglycine, CH 3NH 2, N,N-Me 2Thr and di-α-amino acid containing diphenylether moiety. The peptide sequence except one labile amino acid residue was determined by partial hydrolysis, chemical cleavage, and the Edman degradation. The unknown amino acid was finally deduced to be the dehydroamino acid containing epoxide, resulting in an elucidation of whole structure of the antibiotic.

Molecular analysis of the melting behaviour of poly(aryl-ether-ether-ketone)

The melting behaviour of poly(aryl-ether-ether-ketone) (PEEK) was investigated using Fourier transform infra-red ( FTir) spectroscopy and differential scanning calorimetry (d.s.c.) as part of a study of a carbon fibre reinforced PEEK composite. Digital spectral subtraction was utilized to derive the characteristic spectra of the amorphous and crystalline phases of the polymer. Local order in the amorphous phase of PEEK was observed when the polymer was melted below its equilibrium melting temperature ( T∗ m = 395° C ). The local order is associated with the diphenyl ether moiety. Molecular segments in the ordered regions may assume different orientations on the surface of potassium bromide salt crystals, depending upon whether PEEK is processed at 380°C or 400°C. Molecular analysis by FTir correlates well with data obtained by d.s.c.

OF4949, new inhibitors of aminopeptidase B. II. Elucidation of structure.

The structures of OF4949-I, II, III and IV were identified by analysis of the products of their chemical degradation and by 1H NMR, 13C NMR, and mass spectrometry. These compounds were new cyclic peptides containing diphenyl ether as a chromophore. OF4949-I had two amino acids, beta-hydroxy-L-asparagine and 4-methylisodityrosine. The structural differences between I and II and between III and IV lay solely in the diphenyl ether moiety; the phenolic hydroxyl group in II and IV was methylated in I and III. OF4949-III and IV contained L-asparagine instead of the beta-hydroxy-L-asparagine moiety of I and II.

Teicoplanin, antibiotics from Actinoplanes teichomyceticus nov. sp. V. Aromatic constituents.

Oxidative and hydrolytic degradation reactions were carried out on teicoplanin in order to characterize the aromatic portion of the molecule and relate it to the other members of the class of glycopeptide antibiotics. Seven aromatic rings, obtained as triphenyl ether, diphenyl ether, and diphenyl moieties after oxidation nd hydrolysis of teicoplanin, were identified. They are present in teicoplanin as aromatic amino acids and constitute the peptidic part of the molecule. The diphenyl ether and diphenyl moieties, which were isolated both as esters after oxidation and as alpha-amino acids after acid hydrolysis clearly indicate the nature of the corresponding amino acids in teicoplanin. The triphenyl ether moiety, which was isolated only as ester, allows the hypothesis that the corresponding amino acids are the same as those of the other glycopeptide antibiotics.

Synthesis1 of Ring-Labeled L-Thyroxine-C14

Although I/sup 131/-labeled and carboxyl C/sup 14/-labeled thyroxine have been used to study the metabolism of thyroid hormone, these labels are readily removed physiologically, and knowledge about the metabolic fate of the diphenyl ether moiety of the molecule is incomplete. Preliminary investigation of this aspect of thyroxine metabolism, L -thyroxine labeled with C/sup 14/ in the phenolic ring was synthesized. To utilize a previous method for the convenient preparation of L-thyroxine from p-methoxyphenol, it was necessary to prepare this intermediate from phenol-C/sup 14/ by the reaction scheme which is shown. Then, by modification of the Chalmers method for the condensation of N- acetyl-3,5-dinitroL-tyrosin; ethyl ester with p-methoxyphenol and conversion of the condensation product to L-thyroxine, it was possible to prepare L-thyroxine-C/ sup 14/ in 12 steps in an over-all yield of 2.6%. The detailed procedure is described. The starting material, uniformly labeled C/sup 14/-phenol (specific activity 1.3 mC/mmole, 2.3 mmoles or 216 mg) was converted to phenyl-C/sup 14/- benzenesulfonate by addition of benzensefulfonyl chloride in pyridine. The product was converted to the pnitrophenyl derivative (with KNO/sub 3/ and concentrated H/sub 2/SO/sub 4/ which was converted by alkali to p-nitrophenol-C/ sup 14/. This was treated with diazomethane to form p-nitroanisole-C/sup 14/more » which was reduced with Pt and H/sub 2/ to p-aminoanisole-C/sup 14/. By diazotization p-methoxyphenol-C/sup 14/ was prepared, which was converted to L- thyroxine-C/sup 14/ by the Chalmers procedure. Characterization of the labeled hormone by paper chromatography and assay of its endocrine potency are described. The L-thyroxine-C/sup 14/ exhibited biological activity equivalent to authentic L -thyroxine when tested by the inhibition of propylthiouracil-induced goiters in rats and the suppression of thyroidal I/sup 131/ uptake. (BBB)« less