Yasuhiro Imakura

Bitter phenyl propanoid glycosides from campsis chinensis

Abstract A new bitter phenyl propanoid glycoside, campneoside I, was isolated, together with acteoside and campneoside II, from the leaves of Campsis chinensis . The stereostructure of campneoside I was established as R,S -β-methoxy-β-(3′,4′-dihydroxyphenyl)-ethyl- O -α- L -rhamnopyranosyl(1 → 3) β- D -(4- O -caffeoyl)-glucopyranoside on the basis of the spectroscopic studies and chemical evidence.

Effect of alkaloids isolated from Amaryllidaceae on herpes simplex virus

Studies were carried out on the effects of Amaryllidaceae alkaloids and their derivatives upon herpes simplex virus (type 1), the relationship between their structure and antiviral activity and the mechanism of this activity. All alkaloids used in these experiments were biosynthesized from N-benzylphenethylamine; the apogalanthamine group was synthesized in our laboratory; those which may eventually prove to be antiviral agents had a hexahydroindole ring with two functional hydroxyl groups. Benzazepine compounds were neither cytotoxic nor antiviral, but many structures containing dibenzazocine were toxic at low concentrations. It was established that the antiviral activity of alkaloids is due to the inhibition of multiplication and not to the direct inactivation of extracellular viruses. The mechanism of the antiviral effect could be partly explained as a blocking of viral DNA polymerase activity.

Terpenoids and aromatic compounds from Daphne oleoides ssp. oleoides

Abstract The methanol extract of dried stems of Daphne oleoides Schreber ssp. oleoides afforded two new sesquiterpenoids: 4,10,11-guaiatriene-3-one-15-al and 4, 10, 11-guaiatriene-3,9-dione, named oleodaphnal and oleodaphnone; two new diterpenoids, genkwadaphnin-20-palmitate and gnidicin-20-palmitate; and thirteen known compounds. Their structures were established on the basis of spectroscopic studies.

Iridoid glucosides from Campsis chinensis

Abstract Two new iridoid glucosides, 5-hydroxycampenoside and cachineside I, were isolated together with tecomoside from leaves of Campsis chinensis and their structures were elucidated. The absolute stereochemistry of 5-hydroxycampenoside has been established by X-ray analysis, and the structural correlation between 5-hydroxy-campenoside and tecomoside has been determined by spectral and chemical experiments.

Four stilbenes from Salacia lehmbachii

Abstract New stilbene derivatives designated lehmbachols A-D were isolated from the bark of Salacia lehmbachii , collected in Papua New Guinea. Their structures were established from spectroscopic evidence as 1-[1-methoxy-1-(3-methoxy-4-hydroxyphenyl)methyl]-2-(3,5-dimethoxyphenyl)-3-(3-methoxy-4-hydroxyphenyl)-4,6-dihydroxy-2,3-dihydro-1H-indene and its diastereoisomer, 1-[1-ethoxy-1-(3-methoxy-4-hydroxyphenyl)methyl]-2-(3,5-dimethoxyphenyl)-3-(3-methoxy-4-hydroxyphenyl)-4,6-dihydroxy-2,3-dihydro-1H-indene and 2-(3-methoxy-4-hydroxyphenyl)-5,7-dihydroxy-8-(3,5-dimethoxy-4-hydroxyphenyl)-2,3,9,10-tetrahydro-8H-indeno [1,2-c] furan, respectively.

BINDING AFFINITY OF CU(II)-VP-16 (ETOPOSIDE) COMPLEX AND ITS ANALOGUES TO DNA AND HYDROXYL RADICAL GENERATION DURING DNA STRAND BREAKS

Conformational effects and affinities of VP-16 (etoposide) and its derivatives to DNA in the presence of Cu(II) ion were examined by circular dichroic (CD) spectra. The Cu(II)/Cu(I) redox kinetics and the hydroxyl radical (.OH) generation from the Cu(II)-complexes were estimated by the stopped-flow kinetics. Based on the results, DNA-cleaving activity of Cu(II)-complexes of VP-16 has been shown to be related with binding affinity of the complex to DNA, Cu(II)/Cu(I) redox and .OH generation, emphasising the mechanism of generated .OH attack to DNA.

Effects of CpG methylation to double stranded DNA breaks by Cu(II)-podophyllotoxin derivative complexes

Abstract Site-specific double stranded DNA breaks by ·OH radicals generated from podophyllotoxin related compounds in the presence of Cu(II) ion were investigated and the neighboring effects of 5-methylcytosine on double stranded DNA cleavage, especially on methylated CpG sites, were evaluated.

Antimalarial artemisinin analogs : synthesis of 2,3-desethano-12-deoxoartemisinin-related compounds

2,3-Desethano-12-deoxoartemisinin-related compounds ((+)-16a) and ((-)-16b) have been synthetized from R-(+)-citronellal (7) by a stereoselective manner, which is applied to the synthesis of various novel antimalarial artemisinin analogs

Three β-coumaranones from Sparaxis tricolor

Three new β-coumaranones, sparanone A, sparanone B and sparanoside B, were isolated from bulbs of Sparaxis tricolor. Their stereostructures were established on the basis of chemical evidence and spectroscopic studies.

Regioselective cleavage reaction of the methylenedioxy ring in aromatic compounds containing electron-withdrawing groups with sodium alkoxides-alcohols in dimethyl sulfoxide

The reaction of 6-bromopiperonal (I) with sodium alkoxides (MeONa or PhCH 2 ONa)-alcohols (MeOH or PhCH 2 OH), and sodium alkoxides (MeONa, PhCH 2 ONa or PhONa)-phenol (PhOH) in dimethyl sulfoxide gave 3-hydroxybenzene derivatives and 4-hydroxybenzene derivative , respectively. The reactivity and formational mechanism of various nucleophilic reagents (alkoxide anions) formed from the alcohols and phenol by sodium alkoxides in the regioselective cleavage reactions are discussed