Nobuyuki Harada

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Attempts to fabricate mechanical devices on the molecular level have yielded analogues of rotors, gears, switches, shuttles, turnstiles and ratchets. Molecular motors, however, have not yet been made, even though they are common in biological systems. Rotary motion as such has been induced in interlocked systems and directly visualized for single molecules,(More)
Prodigiosins are natural red pigments that have multi-biological activities. Recently, we discovered a marine bacterial strain, which produces a red pigment. Extensive two-dimensional nuclear magnetic resonance and mass spectrometry analysis showed that the pigment is a prodigiosin analogue (PG-L-1). Here, we investigated the effect of PG-L-1 on NADPH(More)
To determine the absolute configuration of chiral compounds, theoretical calculations of ECD spectra have been extensively carried out, where the shape of component CD Cotton effects was approximated by the Gaussian distribution curve. However, in some articles, errors are found in the equations of Gaussian curve expressing CD Cotton effects. In this short(More)
2',4'-Dihydroxy-3',5'-dimethyl-6'-methoxychalcone 1, its isomeric flavanone 5-O-methyl-4'-desmethoxymatteucinol 2 and 2'4'-dihydroxy-6'-methoxy-3'-methylchalcone 3 were isolated from the leaves of S. samarangense using a bioassay-directed scheme. In an oral glucose tolerance test, at a dosage of 1.0 mg/20 g mouse, 1 and 2 significantly (alpha = 0.05)(More)
Stereochemical studies of a cruciferous oxindole phytoalexin, (S)-(-)-spirobrassinin [(-)-4], and its oxazoline analogue, spirooxazoline (11), were carried out. Racemic spirobrassinin [(+/-)-4] was synthesized by SOCl(2)- or MsCl-mediated cyclization of dioxibrassinin [(+/-)-8]. Treatment of (3-hydroxyoxindol-3-yl)methylammonium chloride [(+/-)-9] with(More)
To determine the absolute configurations of chiral compounds, many spectroscopic and diffraction methods have been developed. Among them, X-ray crystallographic Bijvoet method, CD exciton chirality method, and the combination of vibrational circular dichroism and quantum mechanical calculations are of nonempirical nature. On the other hand, X-ray(More)
Two new polyacetylenic acids, corticatic acids D (2) and E (3), have been isolated from the marine sponge Petrosia corticata along with the known corticatic acid A (1) as geranylgeranyltransferase type I (GGTase I) inhibitors. Their structures were elucidated on the basis of spectroscopic and chemical methods. Compounds 1-3 inhibited GGTase I from Candida(More)
Enantiopure phthalides 2 and 5-8 were synthesized via enantioresolution of the corresponding alcohols with a chiral auxiliary of camphorsultam dichlorophthalic acid, (1S,2R,4R)-(-)-CSDP acid 3, followed by solvolysis with KOH in MeOH and the catalytic oxidation of chiral glycols with iridium complex 28. The absolute configurations of phthalides 2 and 5-8(More)
Enantiopure (2,6-dimethylphenyl)phenylmethanol (+)-(3) and analog (+)-(4) were prepared and their CD spectra were found opposite to that of (2-methylphenyl)phenylmethanol (R)-(-)-(2), the absolute configuration of which was previously established by X-ray crystallography. Therefore the S absolute configuration was once assigned to (+)-3 and (+)-4. After(More)