The synthesis of benzo[b]phenanthro[d]thiophenes and anthra[b]benzo[d]thiophenes

The synthesis of benzo[b]phenanthro[2, 3-d]thiophene ( 5 ), benzo[b]phenanthro[4, 3-d]thiophene ( 6 ), benzo-[b]phenanthro[2, 1-d]thiophene ( 9 ), benzo[b]phenanthro[3, 2-d]thiophene ( 14a ), anthra[1, 2-b]benzo[d]thiophene ( 24 ), anthra[2, 3-b]benzo[d]thiophene ( 29 ) and anthra[2, 1-b]benzo[d]thiophene ( 30 ) is described as well as the preparation of 13-methylbenzo[b]phenanthro[3, 2-d]thiophene ( 14b ).     

Radical copolymerization of sulfur dioxide and chloroprene

The radical copolymerization of sulfur dioxide and chloroprene (CP) in benzene was carried out, especially as a function of the total monomer concentration ([SO₂] + [CP]). The composition of chloroprene polysulfones varies mainly with total monomer concentration and with polymerization temperature, but depends very slightly on feed composition. The microstructure of chloroprene units in chloroprene polysulfone was such that the trans-1,4 unit was predominantly over the cis-1,4 unit. Thus it would seem possible to rule out both radical copolymerization mechanisms, i.e., propagation of separate monomers as explained by the Lewis-Mayo equation, and propagation processes involving a monomer charge-transfer complex.     

Improvement of chemical analysis of antibiotics. VIII. Application of prepacked C18 cartridge for the analysis of tetracycline residues in animal liver

A simple, rapid and precise analytical method for tetracycline (TC) residues in the liver of slaughtered animals has been established. The recoveries of oxytetracycline (OTC), TC, chlortetracycline (CTC) and doxycycline (DC) from beef liver spiked at the level of 1.0 ppm were 87.7, 87.5, 79.6 and 67.5% with coefficients of variations of 1.01-2.87%. Detection limits in beef liver were 0.05 and 0.1 ppm for OTC and TC and for CTC and DC, respectively. It is also possible to apply this method to the analysis of residual TCs in various foods with the same recovery, accuracy and detection limits as in the case of beef liver.     

EXCITED STATE DYNAMICS OF RETINAL PROTEINS AS STUDIED BY FOURIER TRANSFORM OF OPTICAL ABSORPTION SPECTRUM—I. DEVELOPMENT OF ANALYTICAL METHOD

Abstract— We significantly improved the analytical method for the study of excited state dynamics of pigments, by means of the time correlation function (tcf) of the vibrational wavepacket which is produced by the Fourier transform of experimentally obtained optical absorption spectra (FTOA). Applying the tcf method to the spectra of rhodopsin at 0°C and -180°C, we observed specific peaks which are slightly different between 0°C and -180°C in the early time region (1–130 fs) of the absolute value of tcf, representing a characteristic propagation of the wavepacket along a reaction coordinate pertinent to the cis-trans photoisomerization of the chromophore accompanying the motion of protein moiety. From the analysis of phase angle propagation, we obtained a rather small relaxation energy, 6–7 kcal/mol. Based on these results, we can say that FTOA analysis is useful as one of the most powerful techniques for the study of very early procedures in the excited state dynamics of pigments.     

Stereocontrolled synthesis and determination of the c-24 and 25 stereochemistry of glaucasterol

(24S,25S)- and (24R,25R)-24,26-Cyclocholesta-5,22E-dien-3β-ols (1a and 1b) were synthesized stereoselectively. Their ₁H NMR comparison with natural glaucasterol (1) allowed to conclude that 1 possesses 24S,25S stereochemistry.     

Thermodynamic properties of the classical Heisenberg chain with nearest- and next-nearest-neighbor interactions

Exact results for the thermodynamic quantities of the one-dimensional classical Heisenberg model with nearest- and next-nearest-neighbor exchange interactions are obtained by means of the numerical transfer matrix method. For a wide range of exchange constants, the system exhibits helical short-range order on which we focus our attention. We find that the Fourier-transformed spin correlation function shows a maximum with asymmetric shape at the characteristic wave-number ±q _m (0, ±). The correlation length defined as the inverse of the width atq=q _m obeys a simple scaling law and shows a power-law singularity at zero temperature. Results for the heat capacity and the susceptibility are also presented and discussed in connection with the helical short-range order.     

Trace analysis of microcystins in environmental samples

Microcystins, the cyclic heptapeptide toxins produced by cyanobacteria such as Microcystis sp., show potent hepatotoxicity and tumor-promoting activity through inhibition of protein phosphatases 1 and 2A. A toxic incident resulting in the death of 50 people in Brazil in 1996 was due to microcystins in water used for hemodialysis. Microcystins are now threatening human health and life, but many problems associated with microcystins remain unsolved. This report describes how to analyze trace amounts of microcystins in complicated matrixes such as liver tissue, lake water, and sediments.     

High‐Pressure Synthesis of Manganese Oxyhydride with Partial Anion Order

The high‐pressure synthesis of a manganese oxyhydride LaSrMnO_3.3H_0.7 is reported. Neutron and X‐ray Rietveld analyses showed that this compound adopts the K₂NiF₄ structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO₄ that result in only oxygen‐deficient phases down to LaSrMnO_3.5. This suggests that high H₂ pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition‐metal oxyhydrides. Magnetic susceptibility revealed a spin‐glass transition at 24 K that is due to competing ferromagnetic (Mn²⁺–Mn³⁺) and antiferromagnetic (Mn²⁺–Mn², Mn³⁺–Mn³⁺) interactions.