Synthesis of novel organoselenium as catalyst for Baeyer-Villiger oxidation with 30% H2O2

A novel diselenide was synthesized in good yield via only four steps from phenol, and was employed as the catalyst for the Baeyer-Villiger oxidation with 30% H₂O₂ to obtain lactones in good yields.     

Three New Lanostane Triterpenoids from Inonotus obliquus

Three new lanostane‐type triterpenoids, inonotsulides A, B, and C ( 1 – 3 , resp.) were isolated from the sclerotia of Inonotus obliquus (Pers .: Fr.) (Japanese name: Kabanoanatake; Russian name: Chaga). Their structures were determined to be (20R,24S)‐3β,25‐dihydroxylanost‐8‐en‐20,24‐olide ( 1 ), (20R,24R)‐3β,25‐dihydroxylanost‐8‐en‐20,24‐olide ( 2 ), and (20R,24S)‐3β,25‐dihydroxylanosta‐7,9(11)‐dien‐20,24‐olide ( 3 ) on the basis of chemical transformation, NMR spectroscopy including 1D and 2D (¹H,¹H‐COSY, NOESY, HMQC, HMBC), EI‐MS, and single‐crystal X‐ray analysis.     

Synthesis and evaluation of 3-methyl-4-oxo-6-phenyl-4,5,6,7-tetrahydrobenzofuran-2-carboxylic acid ethyl ester derivatives as potent antitumor agents

For the construction of new combinatorial libraries, a lead compound was created by replacing the core structure of a hit compound discovered by screening for cytotoxic agents against a tumorigenic cell line. The newly designed compound maintained biological activity and allowed alternative library construction for antitumor drugs.     

Ruthenium(II)-catalyzed hydrogenation of carbon dioxide to formic acid. Theoretical study of real catalyst, ligand effects, and solvation effects

Ruthenium-catalyzed hydrogenation of carbon dioxide to formic acid was theoretically investigated with DFT and MP4(SDQ) methods, where a real catalyst, cis-Ru(H)2(PMe3)3, was employed in calculations and compared with a model catalyst, cis-Ru(H)2(PH3)3. Significant differences between the real and model systems are observed in CO2 insertion into the Ru(II)-H bond, isomerization of a ruthenium(II) eta1-formate intermediate, and metathesis of the eta1-formate intermediate with a dihydrogen molecule. All these reactions more easily occur in the real system than in the model system. The differences are interpreted in terms that PMe3 is more donating than PH3 and the trans-influence of PMe3 is stronger than that of PH3. The rate-determining step is the CO2 insertion into the Ru(II)-H bond. Its deltaG(o++) value is 16.8 (6.8) kcal/mol, where the value without parentheses is calculated with the MP4(SDQ) method and that in parentheses is calculated with the DFT method. Because this insertion is considerably endothermic, the coordination of the dihydrogen molecule with the ruthenium(II)-eta1-formate intermediate must necessarily occur to suppress the deinsertion. This means that the reaction rate increases with increase in the pressure of dihydrogen molecule, which is consistent with the experimental results. Solvent effects were investigated with the DPCM method. The activation barrier and reaction energy of the CO2 insertion reaction moderately decrease in the order gas phase > n-heptane > THF, while the activation barrier of the metathesis considerably increases in the order gas phase < n-heptane < THF. Thus, a polar solvent should be used because the insertion reaction is the rate-determining step.     

Thallium selenate (Tl2SeO4) in a paraelastic phase by X‐ray powder diffraction

The structure of thallium selenate, Tl₂SeO₄, in a paraelastic phase (above 661 K) has been analysed by Rietveld analysis of the X‐ray powder diffraction pattern. Atomic parameters based on the isomorphic K₂SO₄ crystal in the paraelastic phase were used as the starting model. The structure was determined in the hexagonal space group P6₃/mmc, with a = 6.2916 (2) Å and c = 8.1964 (2) Å. From the Rietveld refinement it was found that two orientations are possible for the SeO₄ tetrahedra, in which one of their apices points randomly up and down with respect to [001]. One Tl atom lies at the origin with symmetry, the other Tl and one of the O atoms occupy sites with 3m symmetry, the Se atom is at a site with symmetry and the remaining O atom is at a site with m symmetry. Furthermore, it was also found that the Tl atoms display anomalously large positional disorder along [001] in the paraelastic phase.     

Separation of neutral and basic enantiomers by cyclodextrin electrokinetic chromatography using anionic cyclodextrin derivatives as chiral pseudo-stationary phases

Separations of neutral and basic racemates were performed using five different anionic cyclodextrin (CD) derivatives as chiral selectors, viz. carboxymethylated β-CD, β-CD phosphate sodium salt, sulfobutyl ether β-CD sodium salt, carboxymethylated γ-CD, and γ-CD phosphate sodium salt. For the separation of neutral racemates, an untreated fused silica capillary was employed and various neutral racemates were successfully separated. Since the pH of the buffer affected the electroosmotic flow (EOF), the resolution was improved by changing the buffer pH. A polyacrylamide coated capillary was employed for the separation of basic racemates to suppress EOF and to prevent adsorption of cationic analyte on the capillary surface. By choosing an appropriate type and concentration of anionic CD, about 40 basic racemates were successfully separated. Some rough binding constants of basic analytes with an anionic β-CD were measured to discuss the optimum concentration of the CD. The migration direction was dependent on the binding constants and the concentration of the CD. The analyte strongly bound to the anionic CD migrated towards the anode but the weakly bound one moved towards the cathode. Anionic γ-CDs were also very useful for the separation of basic enantiomers. Five neutral CDs were employed as chiral selectors to compare selectivity between charged and neutral CDs, and eleven racemates could only be resolved using anionic CDs. The separation of some basic racemates in human plasma was also described. The direct injection of plasma samples was possible for some enantiomers that did not interact strongly with plasma proteins.     

Ultramicro determination of organic halogens using sealed tube dry combustion method

A sealed tube dry combustion method that is simple, accurate, and precise for ultramicro determination of halogens in organic compounds has been developed. Samples below 1 mg are heated at 580 °C for 1 h in an electric furnace. After the combustion and absorption of the gaseous halogen, the interior of the tube is rinsed. Subsequent titration is carried out potentiometrically with silver nitrate and yielded standard deviations of 0.21% for chlorine, 0.17% for bromine, and 0.25% for iodine.     

Determination in plasma of angiotensin-converting enzyme inhibitor by inhibitor-binding assay.

A method of determining a new angiotensin-converting enzyme inhibitor (CS-622) and its active metabolite (RS-5139) in plasma by inhibitor-binding assay has been developed using high-performance liquid chromatography. The assay is based on the principle that the amount of inhibitor bound to the enzyme is inversely related to the amount of hippuric acid liberated on hydrolysis from the artificial substrate (hippuryl-L-histidyl-L-leucine). Plasma was heated at 60 degrees C for 15 min, to inactivate endogenous enzyme, and preincubated with rabbit-lung angiotensin-converting enzyme at 37 degrees C for 3 min. The artificial substrate (5.75 mg/ml in pH 8.3 phosphate buffer containing sodium chloride) was added to the resulting solution, and the mixture was incubated for 30 min. The reaction was terminated by the addition of 2 M hydrochloric acid. The hippuric acid liberated on hydrolysis was extracted with ethyl acetate and determined by reversed-phase chromatography using methylparaben as an internal standard. The total concentration of the inhibitor and its metabolite were determined by this method after de-esterification by rat-plasma esterase. The standard curve was obtained by the regression analysis of log concentration against logit response. The within-day and day-to-day precision were satisfactory. The proposed method is simple, rapid and sensitive enough to determine angiotensin-converting enzyme inhibitor in plasma.     

Synthesis and biological activities of analogs of a lipid A biosynthetic precursor: 1-O-phosphonooxyethyl-4'-O-phosphono-disaccharides with (R)-3-hydroxytetradecanoyl or tetradecanoyl groups at positions 2, 3, 2' and 3'.

Two novel analogs of a biosynthetic precursor of lipid A (2) were synthesized. The one analog (3) has acyl groups identical to those of 2, and the other (4) has tetradecanoyl groups in place of the (R)-3-hydroxytetradecanoyl groups of 2. Both 3 and 4 possess an alpha-glycosidically-bound phosphonooxyethyl group in place of the alpha-glycosyl phosphate group of 2. Compounds 3 and 4 exhibited definite antitumor activity against Meth A fibrosarcoma and low toxicity in rabbits, as the original compound 2 does. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups barely affected the antitumor activity, but slightly enhanced the toxicity in rabbits.     

Comparison of Bartlett-type adjusted tests in the multiparameter case

Considering some Bartlett-type adjusted tests for a simple hypothesis about a multidimensional parameter, this paper clarifies similarities and dissimilarities with the one-parameter case developed in the 1990s, where a major emphasis is put on the issue posed by Rao and Mukerjee [C.R. Rao, R. Mukerjee, Comparison of Bartlett-type adjustments for the efficient score statistic, J. Statist. Plann. Inference 46 (1995) 137-146] on the power under a sequence of local alternatives. Not surprisingly, there is an infinite number of adjustments which extend Chandra-Mukerjee and Taniguchi approaches to the multiparameter case. Revisiting their ideas, this paper presents four specific cases (type K, K=0,1,2,3) and gives a sufficient condition under which our generalized adjustment for each case is uniquely determined, where type 0 is a counterpart of Chandra and Mukerjee’s original proposal for Rao’s test statistic, whereas the latter three types are introduced as double adjustments related to the Cordeiro and Ferrari approach. If the adjustment of type 1 is made instead of type K, K=0,2,3, it is shown that Chandra and Mukerjee’s approach is equivalent to Taniguchi’s approach in terms of the third-order local power. The same is partially true for type 0, depending on the model under consideration. However, the adjustments of type K, K=2,3, reveal, in general, the non-equivalence of these two approaches in terms of the third-order local power.