Kiyoshi Ezumi

Absorption and phosphorescence spectra of 4-nitropyridine N-oxides and 4- and 3-nitroquinoline N-oxides

Abstract The absorption, phosphorescence and phosphorescence excitation spectra of 4-nitropyridine N-oxide (4NPO) and its methyl derivatives, 4-nitroquinoline N-oxide (4NQO), and 3-nitroquinoline N-oxide (3NQO) were recorded. For 4NPO, the lifetime of phosphorescence, degree of polarization of the phosphorescence and excitation spectra, and the singlet—triplet separation energy were analyzed in detail. The experimental results were also compared with those of SCFMOCI calculation. The following results are reported. (i) The electronic spectra of 4NPO, 4NQO and 3NQO, and the effect of steric hindrance on the spectra are interpreted by the aid of theoretical calculation. At the longest wavelength absorption band the intramolecular charge transfer from the N-oxide group oxygen atom to the nitro group is the main configuration, which may play an important role in the photochemical reaction of these substances. (ii) A blue shift was always observed in the phosphorescence spectra on changing the solvent from ether to isopropyl alcohol, the importance of hydrogen bonding effect on this phenomenon being stressed. (iii) The characteristics of the lowest triplet state of the N-oxides are discussed in detail on the basis of the spectroscopic information. It is concluded that the lowest triplet state is of the nature of a π—π* transition, for 4NPO this being 3 A 1 .

FTIR spectral study of hydrogen bonding in ω-alkanedicarboxylic acids in dilute CCl4 solution

FTIR spectra of the title compounds, HO2C(CH2)nCO2H (n= 4–14)2–12, were measured in dilute CCl4 solution. For compounds 2–7, double cyclic intermolecular hydrogen bonds (II) similar to those observed for glutaric acid 1 were found between the carboxy groups, while 8–12 had cyclic intramolecular hydrogen bonds (IVb). A zigzag correlation was found between the percentage (h) of the double cyclic intermolecular hydrogen-bonded molecules and the n value. The h values of odd-membered compounds were larger than those of even-membered ones and the latter values increased with increasing n value. The h value for 7(n= 9), which forms a 28-membered ring, was 82%. The percentages of the cyclic intramolecular hydrogen-bonded molecules showed the high value of 97% for 12(n= 14). Conformational analyses on compounds 1–12 were carried out using the AM1 method. The hydrogen bondings observed in solution are discussed on the basis of the results.

Classical and three-dimensional quantitative structure-activity analyses of steroid hormones: Structure-receptor binding patterns of anti-hormonal drug candidates

Abstract Previous QSAR (quantitative structure-activity relationships) examples of steroid hormones were briefly surveyed. The absorption and distribution processes and pharmacological activities in which transport factors are critical are governed mainly by molecular hydrophobicity. When the expression of the overall biological activity is controlled by the binding-affinity with the receptor sites as the rate-limiting process, the QSAR pattern is more complicated, because stereoelectronic and hydrogen-bonding effects of substituents or substructures of the molecule are usually involved in the structure-affinity relationships. The binding affinities of a number of androstan-17β-ols and estratrien-17β-ols for androgen and estrogen receptor preparations were experimentally measured and their structure-affinity relationships were analyzed using classical and three-dimensional (CoMFA) QSAR procedures. The regiospecific stereoelectronic properties of the molecule were found to significantly regulate the affinity in each pair of combinations between ligand and receptor species. The hydrophobicity was of minor importance. The classical and CoMFA procedures were complementary to each other, illustrating the “components” involved in physicochemical and structural requirements for the binding affinity. The structural features of epitiostanol, an, antiestrogen, which is an androstanol derivative that has been marketed as an anti-breast cancer agent, agreed very well with the QSAR patterns from the two procedures.