Novel nonionic and cationic hydrogels prepared from N-vinylacetamide

Poly(N-vinylacetamide) (polyNVA) hydrogels were prepared by the copolymerization of N-vinylacetamide (NVA) with divinyl compounds such as methylene-bis-acrylamide, methylene-bis-NVA, and butylene-bis-NVA in a high yield. The resulting hydrogels were more stable than polyacrylamide gel and showed quite a high swelling property in a wide range of pH (1–12) and even in a 5M NaCl solution. They showed not only typical characteristics nonionic hydrogels, but also an amphiphilic property and they swelled well in some organic solvents. When the gels were partially hydrolyzed, cationic hydrogels, i.e., crosslinked poly(NVA-co-vinylamine), were collected. The resulting superabsorbent hydrogels absorbed 400 times of water. © 1993 John Wiley & Sons, Inc.     

Iodine(V) reagents in organic synthesis. Part 2. Access to complex molecular architectures via Dess-Martin periodinane-generated o-imidoquinones

o-Imidoquinones, a rather rare class of compounds, are prepared from anilides by the action of Dess-Martin periodinane (DMP) and water. Their chemistry has been extensively investigated and found to lead to p-quinones and polycyclic systems of diverse molecular architectures. Applications of this methodology to the total synthesis of the naturally occurring compounds, epoxyquinomycin B and BE-10988, are described. Finally, another rare chemical entity, the ketohydroxyamide moiety, has been accessed through this DMP-based synthetic technology, and its reactivity has been studied. Among its most useful reactions is a set of cascade heterocyclic annulations leading to a variety of polycyclic systems of possible biological relevance.     

Wavelength stabilization of a distributed Bragg reflector laser diode by use of complementary current injection

We have demonstrated wavelength stabilization in an 821-nm AlGaAs three-section tunable distributed Bragg reflector (DBR) semiconductor laser diode (LD) that consists of active, phase-controlled, and DBR regions. We injected two separate, complementary currents into the active and the phase-controlled regions in the DBR-LD to suppress wavelength shift. This modulation method was applied to the LD fundamental wave in a second-harmonic-generation (SHG) laser, and the oscillating wavelength was maintained within the phase-matching acceptance range of the SHG device during modulation. A peak blue-violet light power of 62 mW was obtained for the ideal modulation waveform.     

Above-threshold dissociative ionization in the intermediate intensity regime

The problem of dissociative ionization at intermediate intensities ( 10(10)-10(12) W cm(-2)) was studied using the example of I2 and the technique of velocity map imaging. Several new phenomena were observed, including a continuous distribution of recoil energies peaked at zero-kinetic energy, a set of constant dissociative ionic states, and strong anisotropy of the fragment velocity distribution that is diminished by intermediate resonances.     

Carbon-13 separation by IRMPD of trifluoromethane-d0 and -d1

Carbon-13 isotope selectivities and specific decomposition yields in the infrared multiple-photon decomposition of CHF₃ and CDF₃ were examined as a function of wave number using a CO₂ TEA laser. The observed maximum selectivities were 30 for CHF₃ and 55 for CDF₃. The specific decomposition yields in CDF₃ were considerably larger than those in CHF₃.     

Stereospecific synthesis of t,t-1,2,3-trisubstituted cyclopentanes and of angularly disubstituted t-hydrindanols

Anodic oxidative decarboxylation of endo-3-methoxycarbonyl-7-oxabicyclo[2.2.1]heptane-endo-2-carboxylate anion gave exclusively an oxygen-assisted Wagner-Meerwein-rearranged product, methyl 3-methoxy-2-oxabicyclo[2.2.1]heptane-anti-7-carboxylate, constituting a method for the stereospecific synthesis of c-3-acyl-t-2-methoxycarbonyl-r-1-cyclopentanols. Synthesis of 7a-methoxycarbonyl-t-hydrindane-3a,1-carbolactones was also attained.     

Room-temperature, continuous-wave 1-W green power by single-pass frequency doubling in a bulk periodically poled MgO:LiNbO3 crystal

Continuous-wave high-power green light generation at room temperature is reported in a single-pass frequency-doubling configuration with bulk periodically poled MgO:LiNbO3 crystal placed outside a diode end-pumped Nd:GdVO4 laser. The MgO:LiNbO3 samples of 6.95-microm domain period, uniform periodicity, and 50% duty cycle along the entire crystal length are fabricated by use of a high-voltage multipulse poling method. A maximum power of 1.18 W at 531 nm with 16.8% conversion efficiency is obtained from a 2-mm-thick, 25-mm-long MgO:LiNbO3 crystal; the corresponding internal green power and conversion efficiency are 1.38 W and 19.6%, respectively, whereas the normalized conversion efficiency is 3.3%/W.     

Peroxidase-like catalytic activity of anion-exchange resins modified with metal-porphyrins in oxidative reaction of hetrocyclic amines with hydrogen peroxide

To elucidate the peroxidase (POD)-like catalytic activity of anion-exchange resins modified with metal-tetrakis(sulfophenyl)porphine (M-TSPP(r)s), an oxidative reaction of seven mutagenic heterocyclic amines (HCAs) with hydrogen peroxide, which reaction is catalyzed by horse radish POD, was investigated in the presence of M-TSPP(r)s. Among six M-TSPP(r)s tested, Mn- and Fe-TSPP(r)s were found to have a relatively strong POD-like activity for HCAs, in particular for a typical HCA, 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ). The optimal condition for the POD-like activity was selected using Fe- and Mn-TSPP(r)s. For evaluation of an oxidation product of IQ produced in the presence of Fe-TSPP(r), the absorption, NMR and FAB-mass spectra thereof were compared with those of an oxidation product of IQ produced by horse radish POD or a chemical oxidizing agent, sodium hypochlorite. When Fe-TSPP(r) was present as a catalysts, IQ was converted into the dimmer (hydorazone type) which has no mutagenic activity in umu-test. It was revealed that Fe- and Mn-TSPP(r)s exhibit a POD-like catalytic activity in oxidative reaction of HCAs with hydrogen peroxide.     

Electroweak interactions at an infinite sublayer quark level. III.CP violation

In a previous paper we proposed the infinite sublayer quark model, in which there exists an infinite number of quarksu and antiquarksu ^c at an infinite sublayer level. By applying the standard model of the electroweak interactions to the weak isospin doublets (u _L ,u _L ^cp ) ^T and (u _L ,u _L ^ct ) ^T , it is shown that there exists only one phase factor, which causesCP violation.     

Total synthesis of apoptolidin: completion of the synthesis and analogue synthesis and evaluation

The total synthesis of apoptolidin (1) is reported together with the design, synthesis, and biological evaluation of a number of analogues. The assembly of key fragments 6 and 7 to vinyl iodide 3 via dithiane coupling technology was supplemented by a second generation route to this advanced intermediate involving a Horner-Wadsworth-Emmons coupling of fragments 22 and 25. The final stages of the synthesis featured a Stille coupling between vinyl iodide 3 and vinylstannane 2, a Yamaguchi lactonization, a number of glycosidations, and final deprotection. The developed synthetic technology was applied to the construction of several analogues including 74, 75, and 77 which exhibit significant bioactivity against tumor cells.