First isolation and characterization of eight regioisomers for [60]fullerene-benzene bisadducts

[reaction: see text]. The [2 + 2] cycloaddition between [60]fullerene and benzyne generated from 4,5-dimethoxyanthranilic acid (4) afforded bisadducts 5 along with the monoadduct. All of the eight possible regioisomers were first isolated by HPLC and then characterized on the basis of MS, NMR, UV-vis, and CD spectroscopies.     

Synthesis of antimicrobial agents. IV. synthesis of 1-hydroxypiperazine dihydrochloride and its applications to pyridone carboxylic acid antibacterial agents

1-Hydroxypiperazine dihydrochloride 7 was prepared and it was applied to the syntheses of new pyridone carboxylic acid antibacterial agents (PCA-antibacterial agents). 1-Cyclopropyl-6,8-difluoro-1,4-dihydro-7-(4-hydroxypiperazin-1-yl)-4-oxoquinoline-3-carboxylic acid 13 showed the most potent antibacterial activity.     

Palladium-catalyzed tandem carbonylation and intramolecular diels-alder reaction of 4-alken-2-ynyl carbonates: a new synthetic method for polycyclic compounds

A new synthetic method for polycyclic compounds via the palladium-catalyzed tandem carbonylation and intramolecular Diels-Alder reaction is described.     

Photo-induced magnetophonon resonance in n-InSb at 4.2°K

Spin-flip and two-phonon as well as normal magnetophonon resonance are observed in CO₂-laser-irradiated photoconductivity in n-InSb at 4.2°K. The effects are attributed to the resonant cooling of photo-excited electrons due to optical phonon emission.     

Preparations of 5-alkylmethylidene-3-carboxymethylrhodanine derivatives and their aldose reductase inhibitory activity

Reactions of 3-carboxymethylrhodanine (1) with aldehydes (2a-u) afforded stereoselectively the 5-mono-alkylmethylidene-3-carboxymethylrhodanines (3a-u). The configuration of the 5-monoalkylmethylidene-3-carboxymethylrhodanine (3k) were examined by X-ray structure analysis and confirmed to be Z-configuration. The stereoselective reaction path was discussed. Several 5-dialkylmethylidene-3-carboxymethylrhodanines (15a-f) and alkylamino derivatives of 3-carboxymethylrhodanines (18a-o) were also prepared. These products were evaluated for aldose reductase-inhibitory potency and half of them exhibited valuable inhibitory potency.     

Enzymic phenol oxidation of N-methylcoclaurine. Studies on the syntheses of heterocyclic compounds. Part cccxxxii

The enzymic phenol oxidation of N-methylcoclaurine (111) with homogenized potato peels in the presence of hydrogen peroxide was examined and found to give a mixture of the dimer (VI) and trimer (VII) with C-O-C head to tail coupling. Furthermore, the same oxidation of III with homogenized rhizome of Nelumbo nucifera Gartner and hydrogen peroxide was also investigated.     

Enantioselective synthesis of (−)-velbanamine and (+)-isovelbanamine using L-glutamic acid as chiral template

Enantioselective synthesis of (?)-velbanamine(1) and (+)-isovelbanamine (2) has been accomplished using l-glutamic acid as chiral template.     

Kinetics and mechanism of the autoxidation of pentaerythrityl tetraheptanoate at 180–220°C

A kinetic and mechanistic study of the autoxidation of liquid pentaerythrityl tetraheptanoate (PETH) at 180–220°C has been carried out utilizing a stirred-flow reactor. The results are consistent with the occurrence of a chain reaction scheme similar to that proposed for n-hexadecane autoxidation, namely, the formation of monohydroperoxides by the intermolecular abstraction reaction (3), the formation of α,γ- and α,δ-dihydroperoxides and α,γ- and α,δ-hydroperoxyketones by intramolecular peroxy radical abstraction reactions (4) and (4*), the bimolecular termination of peroxy radicals, reaction (6), and the rapid conversion of α,γ-hydroperoxyketones to the corresponding cleavage acids and methyl ketones, reaction (7). Comparisons of various rate parameters for the n-hexadecane and PETH systems reveal that the values of k₇ and (k₃/H atom)/(2 k₆)^1/2 are within experimental uncertainties identical for the two systems at 180°C. The proposed reaction scheme includes the concurrent formation of hydroxy radicals and hydroperoxyketone species. The results of kinetic analysis and the experimentally observed isomer distributions of primary and secondary monohydroperoxide products at high and low oxygen pressures suggest that ≈60% of the hydrogen abstractions from PETH at high oxygen pressures occur by hydroxy radicals.     

Low-temperature elastic moduli and internal dilational and shear friction of polymethyl methacrylate

Longitudinal and transverse wave velocity, five kinds of elastic parameters (young, shear and bulk moduli, Lamér; parameter. Poisson's ratio) and dilational and shear internal friction of polymethyl methacrylate were simultaneously measured over a temperature range 68–400K, using the ultrasonic pulse method. All elastic moduli decrease with increasing temperature, suggesting lowering of molecular bonding strength. From dilational and shear internal frictions, the 139, 382, and 385K peaks are interpreted as rotation of x-methyl estel groups, micro Brownian motion of main chains and stress relaxation, and abrupt increases from 242 and 395K are regarded as free motion of side chains and glass transition, respectively. ©1995 John Wiley & Sons, Inc.