Interactive propagation of photosensitive chemical waves on two circular routes

The propagation of chemical waves in the photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated using an excitable field composed of two rings in slight contact, which were drawn using computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. When the initial phase difference between the two chemical waves in the individual rings was smaller than a critical value, this initial value was maintained after collision of the chemical waves. However, when the initial phase difference was larger than this critical value, the phase difference converged to the same value after the second collision. The critical value increased with an increase in the thickness of the rings. These experimental results on the geometry of the excitable field are discussed in relation to the nature of chemical wave propagation. These results suggest that the photosensitive BZ reaction may be useful for creating spatiotemporal patterns that depend on the geometric arrangement of excitable fields.     

Metabolism of tomato steroidal glycosides in humans

Pregnane glycosides have been isolated in small amounts, along with the major components furostanol and spirostanol glycosides, from Dioscoreaceae, Taccaceae, and Solanaceae, suggesting that pregnane glycosides might be biosynthesized from furostanol and spirostanol glycosides. Recently, commercial natural foods composed of diosgenin have been used for the treatment of diseases such as osteoporosis and premenstrual syndrome in women. It is anticipated that diosgenin would be metabolized into a type of steroidal hormone, for instance progesterone, however, this metabolism has not been confirmed. Therefore, we have examined the metabolites in the urine of subjects who ingested tomatoes, which contain a considerable amount of the steroidal glycoside esculeoside A. The occurrence of steroidal hormones in the metabolites has been recognized. It has been proven that when a steroidal glycoside is administered, it is partly metabolized into a type of steroidal hormone exhibiting various physiological activities.     

A facile and stereoselective synthetic method for allylic 1,3-dienyl ethers

The 1,4-elimination reaction of 1-allyloxy-4-methoxy-(2Z)-alkenes with n-butyllithium is shown to proceed in a marked preference to the [2,3] Wittig rearrangement to afford the allylic (1Z,3E)-dienyl ethers in high stereoselectivities. The synthetic utility of this method is demonstrated by the Claisen rearrangement of the dienyl ethers thus obtained.     

Relationship among iodine, bromine and chlorine concentrations in cow's milk in Japan

In order to know the relationship among some elements in biological materials, iodine, bromine and chlorine concentrations in cow's milk samples in Japan were determined by the thermal neutron activation analysis using a low power research reactor and a Van de Graaff accelerator. The iodine contents in cow's milk samples ranged from 0.041 to 0.316 ppm with an average of 0.096 ppm. The bromine and chlorine in these samples ranged from 2.3 to 11.1 ppm and from 475 to 1650 ppm, respectively. The average concentration of the bromine was calculated to be 5.6 ppm and that of the chlorine was 853 ppm. The relationship among iodine, bromine and chlorine concentrations in cow's milk samples in Japan was studied with a regression analysis. It was suggested that the correlation has a power function as follows; Y = K(Z)-A where, Y is elemental concentration in ppm, Z is atomic weight [corrected] of element, A (= 7.4) is exponent and K (= 14.7) is a constant.     

Elimination-addition mechanism for nucleophilic substitution reaction of cyclohexenyl iodonium salts and regioselectivity of nucleophilic addition to the cyclohexyne intermediate

The reaction of 4-substituted cyclohex-1-enyl(phenyl)iodonium tetrafluoroborate with tetrabutylammonium acetate gives both the ipso and cine acetate-substitution products in aprotic solvents. The isomeric 5-substituted iodonium salt also gives the same mixture of the isomeric acetate products. The reaction is best explained by an elimination-addition mechanism with 4-substituted cyclohexyne as a common intermediate. The cyclohexyne formation was confirmed by deuterium labeling and trapping to lead to [4 + 2] cycloadducts and a platinum-cyclohexyne complex. Cyclohexyne can also be generated in the presence of some other mild bases such as fluoride ion, alkoxides, and amines, though amines are less effective bases for the elimination. Kinetic deuterium isotope effects show that the anionic bases induce the E2 elimination (k(H)/k(D) > 2), while the amines allow formation of a cyclohexenyl cation in chloroform to lead to E1 as well as S(N)1 reactions (k(H)/k(D) approximately 1). Bases are much less effective in methanol, and methoxide was the only base to efficiently afford the cyclohexyne intermediate. Nucleophiles react with the cyclohexyne to give regioisomeric products in the ratio dependent on the ring substituent. The observed regioselectivity of nucleophilic addition to substituted cyclohexynes is rationalized from calculated LUMO populations, which are governed by the bond angles at the acetylenic carbons: The less deformed carbon has a higher LUMO population and is preferentially attacked by the nucleophile.     

Amphiphilic guest sorption of K2[Cr3O(OOCC2H5)6(H2O)3]2[alpha-SiW12O40] ionic crystal

An ionic crystal K2[Cr3O(OOCC2H5)6(H2O)3]2[alpha-SiW12O40] x 3H2O (1a) is synthesized by the complexation of a Keggin-type polyoxometalate of [alpha-SiW12O40]4- with K+ and a macrocation of [Cr3O(OOCC2H5)6(H2O)3]+. Compound 1a possesses both hydrophilic and hydrophobic channels in the crystal lattice. The 3 mol mol(-1) of the water of crystallization in 1a resides in the hydrophilic channel. The water of crystallization is removed by the evacuation at 303 K to form the guest-free phase 1b with small changes in the lattice lengths (+/-0.2 A). The water sorption profile is reproduced by the single rate constant. Therefore, the water sorbed probably resides in the hydrophilic channel. Compound 1b sorbs various kinds of polar organic molecules, and the amounts of < or = C3 alcohols are comparable to or larger than that of water, while chlorocarbons with no hydrogen-bonding ability and nonpolar molecules are excluded. Thus, 1b showed the amphiphilic sorption property. The states of the polar organic molecules sorbed in 1b have been quantitatively investigated using ethanol as a probe molecule. The IR, NMR, and single-crystal X-ray diffraction studies combined with the sorption kinetics reveal that ethanol molecules are mainly sorbed into the hydrophilic channel at P/P0 < or = 0.5, while the sorption into the hydrophobic channel is dominant at P/P0 > or = 0.6. Thus, it is demonstrated that ethanol molecules enter both hydrophilic and hydrophobic channels of 1b.     

Synthesis of the C42-C52 part of ciguatoxin CTX3C

The C42-C52 part of ciguatoxin CTX3C (1) was synthesized from tri-O-acetyl d-glucal. The synthetic segment had a tetrahydropyran ring corresponding to the ‘C49-reduced’ L-ring of 1, designed to avoid side reactions due to acid-labile C49 acetal carbon during acidic reductive conditions planned in further synthesis toward 1. The vicinal dimethyl part at C47-C48 was constructed by a stepwise conjugate addition/methylation procedure. The C50-C52 unit was installed by Grignard addition of the C₃ unit followed by spirocyclization and reductive cleavage of the spirocyclic acetal. Stereoselective assembly of the C42-C44 part was achieved by Brown’s asymmetric crotylboration.     

Capillary zone electrophoresis of albumin-depleted human serum using a linear polyacrylamide-coated capillary: separation of serum alpha-and beta-globulins into individual components

The separation of human serum globulins into individual components was investigated by capillary zone electrophoresis (CZE) using a linear polyacrylamide-coated capillary at pH 7.4. Prior to CZE analysis of globulin components present in serum, it was found that it was necessary to remove albumin. Preparation of albumin-depleted human serum with a HiTrap Blue column allowed the detection of alpha- and beta-globulin components as a series of peaks. Almost all the peaks, both narrow and broad, observed in CZE analysis could be assigned to six globulin components (alpha1-acid-glycoprotein, alpha1 -antitrypsin, haptoglobin, alpha2-macroglobulin, Gc-globulin, and transferrin) by using the technique of antibody-based indirect detection. The CZE results, obtained from serum preparations from three healthy adults and six patients, showed that the CZE system might be capable of detecting qualitative differences among individuals with regard to individual globulin components.