Photochemistry of imidazolides. I. The photo-Fries-type rearrangement of N-substituted imidazoles.

A number of N-substituted imidazoles 1a–1i have been found to photo-isomerize to give the corresponding 2-substituted- and 4(or 5)-substituted imidazoles ( 2a–2i and 3a–3i ). The role of a dissociative path in these reactions has been demonstrated.     

Determination of molecular weight distribution of nylon 12 by gel permeation chromatography

Molecular weight distribution of Nylon 12 was determined with hexafluoroisopropanol/toluene mixture as eluent by gel permeation chromatography. Calibration curve for Nylon 12 was easily obtained from that of polystyrene because the method of universal calibration was applicable among these polymers. The molecular weight distributions of Nylon 12 were always broader than expected by the theory of polymerization, i.e., most probable distribution. This result was not caused by broadening effect in gel permeation chromatography, but by polymerization itself.     

Syntheses and antiulcer activities of 2-aminonorbornene derivatives.

2,2,-Disubstituted norbornenes (1, 2), 2,2-Disubstituted norbornane (3), 2,2,3-trisubstituted norbornenes (4, 5), oxanorbornenes (6) and azanorbornenes (7) were synthesized by the Diels-Alder reaction using alpha, beta-dehydroamino acids as a key step, and their antiulcer activities were examined. The oxazolidine derivative (1h) exhibited the most potent activities against several ulcer-models in rat.     

Comments on the primary and scatter dose-spread kernels used for convolution methods

The basic primary and scatter dose-spread kernels used for convolution methods are usually produced by Monte Carlo simulations with the interaction point forced to the center of a large water phantom. However, it is still not clear whether such Monte Carlo based kernels allow accurate dose calculations with a wide range of field sizes and depths, especially in thorax phantoms. Using the differential primary and scatter concept, this paper proposes another type of basic kernel, with which perfectly accurate primary and scatter absorbed dose calculations can be performed under conditions that the beam is parallel, the incident beam intensity is uniform within and zero outside the field, and the primary beam attenuation coefficient along raylines is not a function of depth and off-axis distance.     

Photochemical aromatic hydroxylation by aromatic amine N-oxides: remarkable solvent effect on NIH-shift

Photooxygenations of 4-²H-anisole ($\text{3}$) and o-xylene ($\text{5}$) by 3-methylpyridazine 2-oxide ($\text{1}$) or pyridine 1-oxide ($\text{2}$) were studied in a variety of solvents at varying irradiation temperatures. Remarkable solvent effect on NIH-shift coupled with their hydroxylation processes was observed.     

Stereoselective adduct formation of α-acylcamphorato-copper(II) chelates with some chiral Lewis bases

The formation constants of the mono-adducts of α-acylcamphorato-copper(II) chelates such as (+)-Cu(facam)₂, (?)-Cu(facam)₂, (+)-Cu(hfbc)₂ and (?)-Cu(hfbc)₂ with some chiral Lewis bases were determined spectrophotometrically in benzene. In order to compare the adduct formation constants obtained with the (+)- and (?)-forms, some pairs of chiral Lewis bases such as 1-amino-2-propanol [(R)(?), (S)(+)], 1-(α-naphthyl)ethylamine [(R)(+), (S)(?)], α-phenyl ethylamine [(R)(+), (S)(?)] and also quinine and quinidine were examined as neutral ligands. Although not very pronounced, the effects of combinations obtained for (+)- or (?)-Cu(II) chelates and (+)- or (?)-ligands indicate that formation constants obtained by the formation of adducts with the ligands having different directions of the optical rotation seems to be superior to those with the same direction.     

An ESR study of radiation damage of bisphenol-A-based epoxy resin at low temperature: Selective hydrogen addition to benzene-ring-forming cyclohexadienyl-type radical

In the γ-irradiated aromatic epoxy resin, diglycidylether of bisphenol A cured with diaminodiphenylmethane, the cyclohexadienyl-type radical is produced as one of the main radical species. Although both the resin and the hardener contain benzene rings, it is concluded that the cyclohexadienyl-type radical is formed by selective addition of the OH hydrogen to the benzene ring on the resin side. The selectivity is accounted for in terms of electron capture by the benzene ring followed by proton transfer from the OH group which is located in front of the benzene ring. This reaction scheme is further supported by the effect of the addition of an electron scavenger on the radical yield as well as by the photobleaching behavior of the radicals involved.     

Studies on antiallergic agents. I. Synthesis and antiallergic activity of novel pyrazine derivatives.

Various pyrazine derivatives were synthesized and their antiallergic activity was examined. The inhibitory activity on allergic histamine release of the compounds bearing a 5-tetrazolyl group was more potent than that of the corresponding carboxyl derivatives. The introduction of -CONH- or -NHCO- between the pyrazine ring and the 5-tetrazolyl group as a spacer greatly enhanced the activity. N-(1H-Tetrazol-5-yl)-2-pyrazinecarboxamide (I-3) was estimated to exhibit nearly the same potency as disodium cromoglycate (DSCG). The structure-activity relationship among various derivatives modified by introducing some substituents onto the 3-, 5- or 6-position of the pyrazine ring of I-3 was investigated. The activity remained unchanged or was reduced when such substituents as methyl, chloro, methoxy, methylamino and dimethylamino were introduced at the 3- or 5-position. In contrast, 6-substitution with various alkylamino groups more or less increased the activity. Among them, the 6-dimethylamino (I-17c) and 6-(1-pyrrolidinyl) (I-34) derivative were proved to be most potent. The IC50 values (concentration which produces 50% inhibition of the allergic histamine release) of I-17c and I-34 were determined to be 4.7 x 10(-10) and 4.6 x 10(-10) M, respectively. These two compounds produced a potent inhibitory activity on passive cutaneous anaphylaxis (PCA) in rat, not only by the intravenous route (ED50 = 0.0096 mg/kg for both compounds) but also by the oral route (ED50 = 0.19 and 0.18 mg/kg, respectively). On the other hand, when the pyrazine ring of some representative compounds was replaced with a pyridine ring, the inhibitory activity on histamine release was significantly reduced.     

Structure-activity relationship (SAR) studies on oxazolidinone antibacterial agents. 1. Conversion of 5-substituent on oxazolidinone

A structure-activity relationship (SAR) study on 5-substituted oxazolidinones as an antibacterial agent is described. The oxazolidinones, of which 5-acetylaminomethyl moiety was converted into other functions, were prepared and evaluated for antibacterial activity. Elongation of the methylene chain (8) and conversion of the acetamido moiety into guanidino moiety (12) decreased the antibacterial activity. The replacement of carbonyl oxygen (=O) by thiocarbonyl sulfur (=S) enhanced in vitro antibacterial activity. Especially, compound 16, which had the 5-thiourea group, showed 4-8 stronger in vitro activity than linezolid. Our SAR study revealed that the antibacterial activity was greatly affected by the conversion of 5-substituent.     

Synthesis and reactivities of 10-S-3 trithiadiazapentalene derivatives

1,3-Bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidinethiones 3a-f reacted with bromine to give trithiadiazapentalene derivatives 5a-f , bearing the exocyclic C-N double bonds, in moderate yields. The molecular structure of 5b was elucidated by the X-ray crystallographic analysis. The treatment of 5b-f with hydrochloric acid gave the ring-opening products, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazo-lidinones 9b-f , accompanied by the production of elemental sulfur. Reduction of 5b , 5d , and 5e with sodium borohydride gave the ring-opening compounds, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidines 13b , 13d , and 13e respectively.