Hiroyuki Momma

Albidosides H and I, two new triterpene saponins from the barks of Acacia albida Del. (Mimosaceae)

Abstract Two new triterpene saponins, albidosides H (1) and I (2), along with the three known saponins were isolated from the barks of Acacia albida. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR studies and mass spectrometry. Albidosides H (1) and I (2) were assayed for their cytotoxicity against HeLa and HL60 cells using MTT method.

Secondary metabolites with antiproliferative effects from Albizia glaberrima var glabrescens Oliv. (Mimosoideae)

Abstract A new 5-dehydroxyflavan, namely Albiziaflavan B or (+)-(2R, 3S, 4R)-3′,4′, 7-trihydroxy-4-methoxy-2,3-trans-flavan-3,4-trans-diol (1) was isolated from the root bark of Albizia glaberrima, together with six known compounds including three flavans: (+)-mollisacacidin (2), (+)-fustin (3) and butin (4); two steroids: chondrillasterol (5) and chondrillasterone (6), and a triterpenoid: lupeol (7). The structure of 1 was established by detailed analysis of its spectroscopic data, especially 1D and 2D NMR spectra, HRESIMS and CD data. Compounds 1–6 were assayed for their antiproliferative effects on two human cancer cells, HeLa at 50 μM (n = 2) and HL60 at 20 μM (n = 2). Compound 3 and 4 were the most active on HL60 with IC50 of 8.1 and 8.3 μM, respectively. Compound 6 was the most active with an IC50 of 4.6 μM on HeLa.

A crystalline molecular gyrotop with a biphenylene dirotor and its temperature-dependent birefringence

Biphenyl contains a direct bond between two phenyl functional groups, and the dihedral angle between the two phenyl groups has been discussed in terms of electronic and steric stabilization. Facile rotation about the C–C bond between the two phenyl components is expected to occur at high temperatures. Here, we report observations of the rotational dynamics of a biphenylene dirotor in a crystalline state in a novel molecular gyrotop. The structure and rotational dynamics of the rotor exhibit remarkable temperature dependence. In accordance with the amplification of the angular displacement of biphenylene inside a crystal with increasing temperature, the birefringence of the single crystal decreased.

Two new 5-deoxyflavan-3,4-diol glucosides from roots of Albizia chevalieri.

Phytochemical investigation of the roots of Albizia chevalieri led to the isolation of two new 5‐deoxyflavan‐3,4‐diol glucosides from roots of A. chevalieri, Chevalieriflavanosides A and B. Their structures were established by 2D NMR techniques, UV, IR, CD, and mass spectrometry. Cytotoxicity of the two compounds was evaluated against acute promyelocytic leukemia HL60 cells. The antibacterial activities of 1 and 2 also were evaluated against Pseudomonas aeruginosa and Staphylococcus aureus using the agar diffusion test. Copyright

Dielectric Relaxation of Powdered Molecular Gyrotops Having a Thiophene Dioxide-diyl as a Dipolar Rotor

The dielectric properties of powdered molecular gyrotops with a thiophenedioxide-diyl are reported. Crystals without a solvent molecule show usual dielectric relaxation spectra due to orientation polarization of the dipolar rotor, while a crystal having ethanol as the crystalline solvent molecule showed novel temperature-dependent dielectric relaxation switching by crystal-to-crystal phase transition, which is induced by hydrogen-bonding interactions between thiophene dioxide and ethanol.

Facile synthesis of 2,5-bis(silyl)selenophene-1,1-dioxide and its photophysical properties

2,5-Bis(trimethylsilyl)selenophene-1,1-dioxide was easily synthesized in 80% yield by reaction of selenophene with the common oxidant m-chloroperbenzoic acid (mCPBA). The oxidation proceeded as a typical consecutive reaction. The kinetic study revealed that the rate of the first oxidation is faster than that of the second oxidation. The structure of the dioxide was identified by NMR spectroscopy and X-ray crystallography. The structural parameters of the dioxide show lower aromaticity as compared with that of selenophene. The HOMO–LUMO transition of the dioxide is remarkably red-shifted as compared with that of selenophene, because of the interactions between the π-orbitals of the ring and the p-orbitals of the oxygen atoms. A dichloromethane solution of the dioxide showed weak fluorescence due to the heavy-atom effect.