Kozo Shibata

Antimicrobial indolequinones from the mid-intestinal gland of the muricid gastropod Drupella fragum

Abstract Three new indolequinones, 6-methoxyindole-4,7-quinone (1), 5-methoxyindole-4,7-quinone (2) and 5-methylindole-4,7-quinone (3) were isolated from the mid-intestinal gland of the muricid gastropod Drupella fragum. The structures of 1 and 2 were established by spectroscopic methods and total synthesis, whereas the structure of 3 was elucidated mainly by NMR spectroscopic analyses. Compounds 1 ∼ 3 exhibited moderate antimicrobial activities against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli with MIC = 6.25 ∼ 50 μg/mL.

Calicogorgins A, B, and C, three bioactive sphinganine derivatives from the gorgonian Calicogorgia sp.

Calicogorgins A, B, and C, three novel sphinganine derivatives possessing lethal and repellent activities against the muricid gastropod Drupella fragum, have been isolated from the gorgonian Calicogorgia sp. and their structures determined on the basis of spectroscopic and chemical evidence.

Calicophirins a and b two new insect growth inhibitory diterpenoids from a gorgonian coral calicogorgia sp

Two new diterpenoids, calicophirins A and B, which exhibit insect growth inhibitory activity against the silkworm, Bombyx mori L., have been isolated from a gorgonian coral Calicogorgia sp. and their structures were fully characterized by extensive 2D-nmr studies

Clerodane diterpenoids from Portulaca cv jewel

Three trans-clerodane diterpenes were isolated from the aerial part of the Portulaca cv Jewel. Their structures were elucidated by spectroscopic methods and chemical correlations.

Crinatusins, Bioactive Diels–Alder Adducts from Cyathocalyx crinatus

From the stems of Cyathocalyx crinatus, a rain forest plant in Borneo, six new Diels–Alder adducts, named crinatusins A1, A2, B1, B2, C1, and C2, together with a known chalcone derivative, 4′,6′-dihydroxy-3′,5′-dimethyl-2′-methoxychalcone, have been obtained. Their structures were determined on the basis of spectroscopic data and chemical methods. Crinatusins showed a lethal toxicity against brine shrimp.

α-Amino acids from a mushroom, Amanita castanopsidis Hongo, with growth-inhibiting activity

Two α-amino acids were isolated from a mushroom, Amanita castanopsidis Hongo. Spectroscopic analyses revealed that one was 2-amino-3-cyclopropyl-butanoic acid and the other the known 2-amino-5-chloro-4-pentenoic acid. Both inhibited root elongation in lettuce seedlings.

Minor diterpenoids from Portulaca cv Jewel

Abstract A trans -clerodane and a diterpenoid with the bicyclo[5.4.0]undecane skeleton were isolated from the aerial part of Portulaca cv Jewel, and their structures were elucidated by spectroscopic methods, chemical correlation and X-ray diffraction analysis. The chemotaxonomical significance is discussed.

Identification in lettuce seedlings of a catecholamine active in synergistically enhancing the gibberellin effect on lettuce hypocotyl elongation

The occurrence of catecholamines in lettuce seedlings was examined by bioassay and gas chromatography-mass spectrometry (GC-MS), since synthetic catecholamines can synergistically enhance the stimulating effect of gibberellic acid (GA3) on hypocotyl elongation of decotylized lettuce seedlings. The catecholamine fraction on TLC obtained from lettuce seedlings synergistically enhanced the GA3 effect on hypocotyl elongation. The analysis of the catecholamine fraction from lettuce seedlings by GC-MS demonstrated the occurrence of dopamine.

Biologically active xenicane diterpenoids from the gorgonian Acalycigorgia sp.

Five new biologically active diterpenoids, acalycigorgins A-E, have been isolated from the gorgonian Acalycigorgia sp. The structures and relative stereochemistry of acalycigorgins were determined by extensive 2D-nmr studies. Acalycigorgins A,B,D and E inhibited the cell division of fertilized ascidian (Styela partita) eggs with IC 50 values of 10, 5.0 and 8.0 μg/ml, respectively, while acalycigorgins C,D and E displayed toxicity in the brine shrimp lethality bioassay (LC 50 =7.6,20 and 1.5μg/ml, respectively)

Peroxo-bridged dinuclear cobalt(III) complexes containing N-glycoside ligands from tris(2-aminoethyl)amine and D-glucose and their reversible dioxygen binding properties

Peroxo-bridged dinuclear cobalt(III) complexes containing N-glycoside ligands from tris(2-aminoethyl)amine (tren) and D-glucose (D-Glc), [{Co[(D-Glc)2tren]}2O2]X3·5H2O (X = Cl 2, Br 3), and their reversible dioxygen binding properties are reported [(D-Glc)2tren = bis(N-D-glucosyl-2-aminoethyl)(2-aminoethyl)amine].