Antifouling Brominated Diterpenoids from Japanese Marine Red Alga Laurencia venusta Yamada.

The marine red algal genus Laurencia has abundant halogenated secondary metabolites, which exhibit novel structural types and possess various unique biological potentials, including antifouling activity. In this study, we report the isolation, structure elucidation, and antifouling activities of two novel brominated diterpenoids, aplysin-20 aldehyde (1), 13-dehydroxyisoaplysin-20 (2), and its congeners. We screened marine red alga Laurencia venusta Yamada for their antifouling activity against the mussel Mytilus galloprovincialis. Ethyl acetate extracts of L. venusta from Hiroshima and Chiba, Japan, were isolated and purified, and the compound structures were identified using 1D and 2D NMR, HR-APCI-MS, IR, and chemical synthesis. Seven secondary metabolites were identified, and their antifouling activities were evaluated. Compounds 1, 2, and aplysin-20 (3) exhibited strong activities against M. galloprovincialis. Therefore, these compounds can be explored as natural antifouling drugs.

DAST-mediated ring-opening of cyclopropyl silyl ethers in nitriles: facile synthesis of allylic amides via a Ritter-type process.

A diethylaminosulfur trifluoride (DAST)-mediated ring-opening reaction of cyclopropyl silyl ethers in nitriles produced allylic amides in moderate to good yields (up to 87%). Time course studies using ReactIR and O-isotopic labeling mechanistic studies suggested that the present reaction occurs via a Ritter-type process, leading to the formation of allylic amides.

Sodium Hypochlorite Pentahydrate as a Reagent for the Cleavage of trans-Cyclic Glycols.

Sodium hypochlorite pentahydrate (NaOCl·5H2O) can be used toward the efficient glycol cleavage of trans-cyclic glycols, which are generally resistant to this transformation. Interestingly, the reaction of cis-cyclic glycols with NaOCl·5H2O is slower than that observed for the corresponding trans-isomer. This trans selectivity is in sharp contrast to traditional oxidants used for glycol cleavage. Acyclic glycols can also react efficiently with NaOCl·5H2O to form their corresponding carbonyl compounds in high yield.

Niobium(V) chloride catalyzed oxidation of dithioacetals with 30% hydrogen peroxide: a concise preparation of bissulfonylmethylene compounds.

The oxidation of dithioacetals with 16 eq of 30% hydrogen peroxide in the presence of 10 mol% niobium(V) chloride at room temperature provides bissulfonylmethylenes in high yields.

Screening test for rapid food safety evaluation by menadione-catalysed chemiluminescent assay.

The chemiluminescent assay of menadione-catalysed H2O2 production by living mammalian cells was proposed to be useful for rapid food safety evaluation. The tested foods were extracted with water, ethanol and dimethylsulfoxide, and each extract was incubated with NIH3T3, Neuro-2a and HepG2 cells for 4h. Menadione-catalysed H2O2 production by living mammalian cells exposed to each extract was determined by the chemiluminescent assay requiring only 10 min, and the viability of the cells was estimated as percentage based on H2O2 production by intact cells. In this study the cytotoxicity of food was rated in order of inhibitory effect on H2O2 production by intact cells. The well known natural toxins such as Fusarium mycotoxin, tomato toxin tomatine, potato toxin solanine and marine toxins terodotoxin and brevetoxin could be detected by the above chemiluminescent assay.

Advantage of menadione-catalyzed chemiluminescent assay for the determination of viable mammalian cell number.

A chemiluminescent assay composed of TCPO [bis(2,4,6-trichlorophenyl)oxalate] and harmless rhodamine B is proposed to be superior in the determination of menadione-catalyzed hydrogen peroxide (H2O2) production by viable mammalian cells to that composed of TCPO and harmful pyrene [Anal. Biochem. 207 (1992) 255-260]. In tests, the proposed assay showed that the measurable concentration of H2O2 and the viable cell number ranged from 10⁻9 to 10⁻³ M and from 2 × 10² to 2 × 106 cells/100 µl/well in the presence of 10% bovine serum, respectively. The measuring time was approximately 10 min. On the other hand, the measurable cell numbers by the colorimetric WST-1 and MTT assays requiring several hours ranged only from 10³ to 104 cells/100 µl/well and from 104 to 105 cells/100 µl/well, respectively. The cytotoxicity of sodium dodecyl sulfate was also observed at intervals of 1 min by the proposed assay, but not by the above colorimetric assays.

Highly selective 30% hydrogen peroxide oxidation of sulfides to sulfoxides using micromixing.

The highly selective oxidation of sulfides to sulfoxides using 30% hydrogen peroxide has been achieved under catalyst-free conditions using a T-shaped micromixer.

Aerobic oxidation of thiols to disulfides catalyzed by trichlorooxyvanadium.

Thiols were converted into disulfide by the aerobic oxidation catalyzed by trichlorooxyvanadium in the presence of molecular sieves 3A.

Synthesis and characterization of a DNA analogue stabilized by mercapto C-nucleoside induced disulfide bonding.

A redox-active nucleobase analogue of a nucleotide was synthesized and incorporated into DNA using phosphoramidite chemistry. An analogue-containing oligonucleotide in the absence of a reducing reagent formed a stable duplex with a substantially higher melting temperature compared to that of a standard DNA duplex of the same length.