Iron-catalyzed cross-coupling of alkenyl sulfides with Grignard reagents

[reaction: see text] The iron-catalyzed cross-coupling reaction of alkenyl sulfides with Grignard reagents is described. While the cross-coupling proceeds efficiently at alkenyl-S bonds, almost no cross-coupling takes place at aryl-S bonds, attesting to a unique selectivity of iron catalysis. The beneficial effect of potentially coordinating 2-pyrimidyl group on sulfur is also described.     

Effects of isoflavone compounds on the activation of phospholipase C.

The effect of isoflavone compounds, genistein and daidzein, on the breakdown of inositol phospholipids in 3T3 cells was studied. Genistein (100 micrograms/ml) inhibited the stimulation of the production of inositol phosphates by bombesin. The stimulated production of inositol phosphates by AlF-4 was also inhibited by genistein (IC50 = 0.6 micrograms/ml) and daidzein (IC50 = 2 micrograms/ml). However, the catalytic activity of phospholipase-C (PLC) in 3T3 cell extracts was not inhibited by these isoflavones. These results suggest that the isoflavones inhibited the activation of PLC at the G-protein or downstream of the sequences in signal transduction. In permeabilized 3T3 cells, the inhibition of AlF-4 plus adenosine triphosphate (ATP)-dependent PLC was recovered by increasing ATP but not AlF-4. Genistein also inhibited the activity of adenosine 5'-[3-O-thiotriphosphate] (ATP[S])-dependent PLC. The effect of genistein and other inhibitors of protein tyrosine kinases and phosphatases suggests that protein tyrosine phosphorylation is not involved in the activation of PLC in 3T3 cells and that AlF-4- and ATP[S]-mediated activation of PLC involves a different mechanism from the tyrosine kinase-mediated activation of PLC. Daidzein and genistein seem to interrupt the ATP-dependent step of PLC activation by a putative G-protein.     

A new organic semiconducting polymer from Cu2+ chelate of poly(vinyl alcohol)and iodine

A new, easily processed, organic semiconductor was prepared from poly(vinyl alcohol) (PVA). The Cu²⁺ chelate of PVA exhibited excellent surface resistivity around 10³ Ω cm^?2 when modified with iodine. Favorable conditions for preparing the chelate effective for the conduction were investigated. The resistivity was significantly affected by the amounts of cupric salts and iodine, satisfactory results being given by more than 15 wt% of cupric salts and about 4 wt% of iodine. Effects of molecular weight of PVA and the chelate structure were also studied.     

Multiple binding of inhibitors in the complex formed by bovine trypsin and fragments of a synthetic inhibitor, 4-[4-(N,N- dimethylcarbamoxylmethoxycarbonylmethyl)phenoxycarbonylphenyl+ ++] guanidinium methanesulfonate (FOY-305)

The crystal of bovine trypsin complexed with a potent inhibitor, 4-[4-(N,N- dimethylcarbamoylmethoxycarbonylmethyl)phenoxycarbonylphenyl ]guanidinium (FOY-305) in the novel orthorhombic from with a low molecular packing density was studied by the X-ray diffraction method. Using synchrotron radiation, the intensity data were collected to 1.8 A resolution. The structure was solved by molecular replacement methods, and refined to an R-factor = 18.0% for 14364 reflections by the restrained least-squares method. The final difference Fourier maps revealed that hydrolyzed inhibitor fragments bind with the protein at multiple sites around the active center of trypsin. The structural feature in the crystalline state probably corresponds to a statistical average of several complexes which would be formed between the inhibitor and trypsin during the binding and releasing process in solution.     

Studies on reactions of the N-phosphonium salts of pyridines—VII : Preparation of peptides and active esters of amino acids by means of diphenyl and triphenyl phosphites in the presence of tertiary amines

Peptides and active esters of amino acids were produced in high yields from carboxyl and amino or hydroxyl components in pyridine with an equivalent amount of diphenyl phosphite or half an equivalent amount of triphenyl phosphite and tertiary amines. Condensation reactions competed with the reaction with a phenoxy group of the phosphite to produce the phenyl ester and were governed by the tertiary amine employed in the reaction. The reactions are assumed to proceed via the N- phosphonium salts of pyridines, similar to those obtained by the oxidation of phosphorus compounds with mercuric salts in pyridine.     

Magnetic Circular Dichroism and Electronic Spectra of Tropothione

The magnetic circular dichroism (MCD) and electronic absorption spectra of tropothione have been measured. The circular-dichroism (CD) spectrum of the β-cyclodextrin complex with tropothione is also reported. The absorption bands of tropothione are assigned.     

Determination of fluvoxamine in rat plasma by HPLC with pre-column derivatization and fluorescence detection using 4-fluoro-7-nitro-2,1,3-benzoxadiazole

A sensitive, simple and reliable method using high-performance liquid chromatographic (HPLC) assay of fluvoxamine (FLU), a selective serotonin reuptake inhibitor (SSRI), in rat plasma after pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was developed in this study. Extracted plasma samples were mixed with NBD-F at 60 degrees C for 5 min and injected into HPLC. Retention times of FLU and an internal standard (propafenone) derivative were 15.5 and 13.5 min, respectively. The calibration curve was linear over the range 0.015-1.5 microg/mL (r2 = 0.9985) and the lower limits of detection and quantification of FLU were 0.008 and 0.015 microg/mL, respectively, in 100 microL of plasma. The derivative sample was stable at 4 degrees C for 1 day. The coefficients of variation for intra-day and inter-day assay of FLU were less than 8.3 and 9.6%, respectively. Other SSRIs and centrally acting drugs did not interfere with the peak of the FLU derivative. The method was applied for analysis of the plasma samples from rats treated with FLU. These results indicate that the method presented is useful to determine the FLU levels in rat plasma of volumes as small as 100 microL and can be applied to pharmacokinetic studies.     

Induced Circular Dichroism Spectra of β- and γ-Cyclodextrin Complexes with Indazolinone and Related Compounds

The magnetic circular dichroism (MCD) spectra of indazolinone, isatine, and 3-iminoisoindolinone and the induced circular dichroism (ICD) spectra of the inclusion complexes with β- or γ-cyclodextrins (CDs) have been measured. The spectra are interpreted by results of the ZINDO calculations. In the presence of cyclodextrin, the OH indazolinone tautomer is main structure that is consistent with that in the DMSO solution. The structures of the inclusion complexes are very different because of the scale of the cavity of cyclodextrin or position of quinone in molecules.     

Induced circular dichroism spectra of 2-(2,4,6-cycloheptatrien-1-ylidene)-4-cyclopentene-1,3-dione included inβ-cyclodextrin

The assignment of the absorption spectra of 2-(2,4,6-cycloheptatrien-1-ylidene)-4-cyclopentene-1,3-dione (1) is reported by measuring the induced circular dichroism spectra of the β-cyclodextrin complex with1. It is concluded from the signs of the induced circular dichroism bands that the first absorption band (17.1×10³–34.3×10³ cm^?1) is composed of three electronic transitions having perpendicular, parallel and perpendicular polarizations with respect to the long axis (z) of1. The second absorption band (34.3×10³–42.8×10³ cm^?1) is composed of two electronic transitions having parallel polarizations with respect to the long axis of1 and the third absorption band (42.8×10³–47.1×10³ cm^?1) has the transition dipole moment perpendicular to the long axis of1. Our experimental assignments are supported by CNDO/S CI calculations.     

Evolution of fluorescein as a platform for finely tunable fluorescence probes

Fluorescence imaging is the most powerful technique currently available for continuous observation of dynamic intracellular processes in living cells. Suitable fluorescence probes are naturally of critical importance for fluorescence imaging, but only a very limited range of biomolecules can currently be visualized because of the lack of flexible design strategies for fluorescence probes. At present, design is largely empirical. Here we show that the carboxylic group of traditional fluorescein dyes, formerly considered indispensable, has been replaced with other substituents, affording various kinds of new fluoresceins. Further, by breaking out of the traditional structure of fluorescein, we developed the first and totally rational design strategy for novel fluorescence probes based on a strict photochemical basis. The value of this approach is exemplified by its application to develop a novel, highly sensitive, and membrane-permeable fluorescence probe for beta-galactosidase, which is the most widely used reporter enzyme.