Noboru Takada

Structural determination of pteriatoxins A, B and C, extremely potent toxins from the bivalve Pteria penguin

Abstract Pteriatoxins A, B and C, extremely potent toxins, were isolated from the Okinawan bivalve Pteria penguin. Their structures were determined based on NMR and MS/MS spectral analyses. Pteriatoxins have polyether macrocycles composed of 6,7-spiro, 5,6-bicyclo and 6,5,6-trispiro ketal rings, the same as in pinnatoxins.

Pinnatoxins B and C, the most toxic components in the pinnatoxin series from the Okinawan bivalve Pinna muricata

Abstract Pinnatoxins B and C, the most toxic components in the pinnatoxin series, were successfully purified from the Okinawan bivalve Pinna muricata . Their gross structures were determined based on NMR and MS/MS spectral analyses. Their stereostructures were mainly determined by transformation reactions. Pinnatoxins B and C, C-34 epimers of each other, have an amphoteric macrocycle composed of 6,7-spiro, 5,6-bicyclo and 6,5,6-trispiro ketal rings, the same as in pinnatoxins A and D.

Isolation and structures of haterumalides NA, NB, NC, ND, and NE, novel macrolides from an Okinawan Sponge Ircinia sp.

Abstract Novel macrolides, haterumalides NA ( 1 ), NB ( 2 ), NC ( 3 ), ND ( 4 ), and NE ( 5 ), were isolated from an Okinawan sponge Ircinia sp. The absolute stereostructure of 1 was determined by spectroscopic analysis and modified Moshers method. Haterumalide NA ( 1 ) showed cytotoxicity against P388 cells and acute toxicity against mice.

Zamamistatin, a significant antibacterial bromotyrosine derivative, from the Okinawan sponge Pseudoceratina purpurea

Abstract Zamamistatin was isolated from the Okinawan sponge Pseudoceratina purpurea. It was determined to be a novel bromotyrosine derivative by careful analysis of 2D NMR spectra and comparison of its 1H NMR spectrum with those of structurally related compounds. The absolute stereostructure of zamamistatin was determined by the modified Moshers method. Zamamistatin exhibited significant antibacterial activity against Rhodospirillum salexigens, which has adhering properties.

Pinnamine, an alkaloidal marine toxin, isolated from Pinna muricata

Abstract Pinnamine, a novel marine alkaloid, was isolated from the Okinawan bivalve Pinna muricata. Pinnamine was determined to be an alkaloid containing a dihydropyrone ring by spectroscopic analysis. The relative stereostructure of pinnamine was determined by an analysis of coupling constants and NOE experiments; the absolute stereostructure was determined by an analysis of the circular dichroism spectrum. Pinnamine exhibited significant acute toxicity against mice.

Hedathiosulfonic acids A and B, novel thiosulfonic acids from the deep-sea urchin Echinocardium cordatum

Abstract Hedathiosulfonic acids A and B were isolated from the deep-sea urchin Echinocardium cordatum and were determined to be novel 6-undecanethiosulfonic acids by 2D NMR, HRMS, and methylation reaction. The stereostructure of hedathiosulfonic acid A was determined by the analysis of its degradation product, a cyclic β-hydroxysulfone. Hedathiosulfonic acids exhibited acute toxicity. We carried out various model reactions of the olefinic compounds with thiosulfonic acids and proved that, as is the case with natural products, synthesized thiosulfonic acid possessing a carbon–carbon double bond was converted into β-hydroxysulfone in the presence of oxygen.

Isolation and structures of hedathiosulfonic acids A and B, novel thiosulfonic acids from the deep-sea urchin Echinocardium cordatum

Abstract Hedathiosulfonic acids A and B were isolated from the deep-sea urchin Echinocardium cordatum , and were determined to be novel 6-undecanethiosulfonic acids by 2D NMR, HRMS, and methylation reaction. Hedathiosulfonic acids exhibited acute toxicity.