Stereoselective synthesis of 1,4-disubstituted 1,3-diene

New synthetic methods for the preparation of 1,3-dienes are described.     

Isomerization of aldehyde-2,4-dinitrophenylhydrazone derivatives and validation of high-performance liquid chromatographic analysis

The most widely used method for qualitative and quantitative analysis of carbonyl compounds is the 2,4-dinitrophenylhydrazine method through the formation of 2,4-dinitrophenylhydrazone derivatives. However, this method may cause an analytical error because 2,4-dinitrophenylhydrazones have both E- and Z-stereoisomers. Purified aldehyde-2,4-dinitrophenylhydrazone demonstrated only the E-isomer. However under UV irradiation and the addition of acid, both E- and Z-isomers were seen. The spectral patterns of Z-isomers were different from those of E-isomers and the absorption maximum wavelengths were shifted towards shorter wavelengths by 5-8 nm. An equilibrium Z/E isomer ratio was observed in 0.02-0.2% (v/v) phosphoric acid solutions. In the case of acetaldehyde- and propanal-2,4-dinitrophenylhydrazones, the equilibrium Z/E isomer ratios were 0.32 and 0.14, respectively. However, when irradiated with ultraviolet light at 364 nm, the isomer ratios were increased beyond this constant ratio and reached 0.55 and 0.33, respectively. Zero-order rates for decreases of aldehyde derivatives were observed under UV irradiation (364 nm), however the decreases of concentration were not observed in phosphoric acid solutions. The best method for the determination of aldehyde-2,4-dinitrophenylhydrazones by HPLC is to add phosphoric acid to both the sample and the standard solution, to form a 0.02-1% acid solution.     

1,1-bis(trimethylsilyl)-1-alkanols as silylcarbene equivalent

Silylcarbenes are generated by the pyrolysis of 1,1-bis(trimethylsilyl)-1-alkanols with elimination of trimethylsilanol.     

Synthesis, characterization and FET properties of novel dithiazolylbenzothiadiazole derivatives

Dithiazolylbenzothiadiazoles easily obtained have high electron affinity and the FET device of a trifluoromethylphenyl derivative exhibited a good n-type performance with high electron mobility.     

Effect of cholesterol or phospholipid incorporation on the chemical stability of the muramyldpeptide derivative B30-MDP in mixed vesicles

Application of the muramyldipeptide derivative B30-MDP to liposomal vaccines will aid in the development of improved high immunogenicity vaccines. To give full play to the effectiveness of B30-MDP as a liposomal vaccine, it is important to evaluate the effect of cholesterol, dimyristoylphosphatidylcholine (DMPC) or distearoylphosphatidylcholine (DSPC) incorporation on the chemical stability of B30-MDP and physicochemical properties of B30-MDP/lipid mixed vesicles from the view point of pharmaceutics.The observed degradation rate constants of B30-MDP by hydrolysis in B30-MDP/cholesterol mixed vesicles were increased with increasing concentration of cholesterol, however, those in B30-MDP/DMPC and B30-MDP/DSPC mixed vesicles were unchanged with increasing concentration of DMPC and DSPC. The degradation behavior of B30-MDP was then compared with physicochemical properties of B30-MDP/lipid mixed vesicles, such as membrane fluidity and particle size. It was apparent that the degradation of B30-MDP in B30-MDP/cholesterol mixed vesicles was influenced by the particle size, but not by the fluidity of the membranes. In the case of B30-MDP/phospholipid mixed vesicles, MDP/phospholipid mixed vesicles, the degradation of B30-MDP was not influenced by either the membranes' fluidity or the particle size of the mixed vesicles.It is considered that the degradation of B30-MDP in the mixed vesicles is dependent on the membrane state, and the addition of cholesterol to B30-MDP vesicle inhibits the mutual interaction of MDP regions, whereas the addition of phospholipids hardly influences the mutual interaction of MDP regions, possibly owing to phase separation between B30-MDP and phospholipids.     

Pd.H-C Interactions. Preparation and Structure of Orthometalated Tetranuclear Complexes of Palladium(II) and Platinum(II)

The reaction of 2-(1-naphthyl)benzothiazoline with palladium(II) acetate leads to helical mononuclear and orthometalated tetranuclear products. The molecular structures of mononuclear palladium(II) [Pd(H1-nabz)(2)] (1) (H(2)1-nabz = 2-N-(1-naphthylmethylideneamino)benzenethiolate), tetranuclear palladium(II) [Pd(4)(1-nabz)(4)] (2) and tetranuclear platinum(II) [Pt(4)(1-nabz)(4)] (3) have been determined by single-crystal X-ray diffraction method. Crystal data for complex 1 are as follows: a = 14.208(3) ?, b = 18.227(4) ?, c = 14.398(8) ?; beta = 94.55(3) degrees; V = 3717.0(23) ?(3); space group = P2(1)/n, Z = 4. Crystal data for the complex 2 are as follows: a = b = 15.798(3) ?, c = 23.728(4) ?; V = 5921.7(20) ?(3); space group = I4(1)/a, Z = 16 for the Pd(1-nabz) unit. Crystal data for the complex 3 are as follows: a = b = 15.496(2) ?, c = 24.348(3) ?; V = 5846.3(20) ?(3); space group = I4(1)/a, Z = 16 for the Pt(1-nabz) unit. The mononuclear palladium(II) complex reveals short ortho-hydrogen.palladium distances of 2.66(7) and 2.48(7) ?. These short distances and (1)H NMR studies provide a M.H-C interaction which can be regarded as a three-center four-electron interaction. The molecular structures of 2 and 3 confirm the formation of unusual tetranuclear compounds featuring a rare C,N,S-tridentate ligand derived from orthometalation of pendant side arm. The structural and chemical properties of the mononuclear palladium(II) complex 1 clearly suggest that 1 is a potential intermediate in the formation of the tetranuclear complex 2 by orthometalation reactions.     

SPECTRAL ANALYSIS OF CHLOROPHYLL a AGGREGATES IN THE PRESENCE OF WATER-SOLUBLE MACROMOLECULES

Abstract— The absorption and fluorescence spectra of chlorophyll a (Chi a) aggregates formed in aqueous solutions of polyvinyl alcohol) (PVA), polyvinyl pyrrolidone) (PVP), and bovine serum albumin (BSA) were analyzed by curve-fitting methods in the wavelength region from 650 to 800 nm. The results indicated that the aggregation of Chi a to polymeric forms such as (Chia–2H₂0), was suppressed in the presence of the macromolecules. The suppression was due to a coordination of macromolecule bound ligands to Chi a and was strongest in BSA and weaker in PVA. There were differences in the spectra even though the same types of polymeric Chi a forms were observed due to characteristically different composition of these forms. Fluorescence patterns indicated that energy was transferred from the shorter to the longer wavelength forms.     

Characterization and crystal structures of copper(II), cobalt(II), and nickel(II) complexes with two kinds of piperidine carboxylic acids

Copper(II) complex with -piperidine-3-carboxylic acid ( -Hpipe-3):[Cu( -pipe-3)₂(H₂O)] and cobalt(II) and nickel(II) complexes with piperidine-4-carboxylic acid (Hpipe-4):[M(Hpipe-4)₂(H₂O)₄]Cl₂ (M: Co, Ni) have been prepared and characterized by means of IR and powder diffuse reflection spectra, thermal analysis, and magnetic susceptibility. The crystal structures of these complexes have been determined by X-ray diffraction. The crystal of [Cu( -pipe-3)₂(H₂O)] is orthorhombic with the space group Pbcn. The copper atom is in a square pyramidal geometry, ligated by two carboxylato oxygen atoms, two nitrogen atoms, and a water molecule. One molecule of this complex consists of either -piperidine-3-carboxylic acid or -piperidine-3-carboxylic acid. The crystals of [M(Hpipe-4)₂(H₂O)₄]Cl₂ are monoclinic with space group P2₁/n. In these complexes the metal atom is in an octahedral geometry ligated by two carboxylato oxygen atoms and four water molecules.     

Study on tumor affinity of technetium-99m-labeled radiopharmaceuticals. (2) 99mTc-Sn-diphosphonate (99mTc-EHDP), 99mTc-Sn-dimercaptosuccinic acid (99mTc-DMSA), and 99mTc-Sn-diethyl stilbestrol diphosphate (99mTc-DSDP)]

The authors have examined the tumor affinity of various 99mTc-labelled radiopharmaceuticals to Ehrlich's tumor for the purpose of delineating positively human malignant neoplasm. This paper includes biologic distributions of 99mTc-Sn-diphosphonate (99mTc-EHDP), 99mTc-Sn-dimercaptosuccinic acid (99mTc-DMSA) and 99mTc-Sn-diethyl stilbestrol diphosphate (99mTc-DSDP, 99mTc-Honvan) as the second report on the tumor affinity to the Ehrlich-bearing mice. (a) Tumor concentration of 99mTc-EHDP was lowest and the positive delineation of implanted tumor with 99mTc-EHDP was poorest in sequential images, though the active accumulation to some soft tissue maglinant neoplasms, the breast cancer and the thyroid cancer, has been reported. (b) Tumor concentration and tumor to blood ratio of 99mTc-DMSA were not so high on the contrary of our expectation that 197Hg-DMSA may show the high tumor concentration and the high tumor to blood ratio like 197Hg chlormerodrin as same renal scanning radiopharmaceuticals. (c) Tumor concentration of 99mTc-DSDP was highest. Tumor to blood concentration ratio, however, was lower than that of the above mentioned radiopharmaceuticals but tumor to liver ratio and/or tumor to lung ratio was over 1.0 at the earlier time. Biologic distribution of 99mTc-DSDP was similar to that of 32P labeled DSDP and then it is presumed that 99mTc is labeled at phosphate ester of DSDP which is dephospholytated immediately by phospholylase in vivo following the intravenous injection. Therefore, it may be assumed that the accumulation mechanism of 99mTc-DSDP to Ehrlich's tumor is related to the phospholylase activity in neoplasms but is not known precisely.     

Highly sensitive determination of a polymeric hindered amine light stabilizer in polypropylene by reactive thermal desorption-gas chromatography using nitrogen-specific detection

Highly sensitive and specific determination of trace amounts of a polymeric hindered amine light stabilizer (HALS) in polypropylene (PP) materials could be established by improving reactive thermal desorption-gas chromatography (RTD-GC) in the presence of an organic alkali, tetramethylammonium hydroxide. By using nitrogen-phosphorus detection, highly selective detection of the HALS-related components was attained. In addition, the use of a polar poly(ethylene glycol) separation column alleviated the adsorption of minor specific pyrolysis products. This modified RTD-GC method allowed the determination of the polymeric HALS (Mr 1900) in PP even for trace concentrations between 100 and 500 ppm, through observing selectively the characteristic products containing a tetramethylpiperidine moiety, which had been impossible to detect under the previous RTD-GC conditions using a non-polar separation column and conventional flame ionization detection.