Transition-Metal-Free Upscaling of 2,5-Furandicarboxylic Acid Synthesis and Investigation of the Reaction Mechanism.

An environmentally friendly oxidation system has proposed for the practical and scalable production of value-added 2,5-furandicarboxylic acid from 1 kg of 5-hydroxymethylfurfural. The system is composed of a simple base, oxygen, and a green solvent, thereby providing a sustainable and economical approach to organic synthesis. To gain insight into the mechanism of this oxidation process, NMR spectroscopic analysis and kinetic study are used for the mechanistic investigation of this environmentally friendly oxidation process.

Acetaldehyde: A Small Organic Molecule with Big Impact on Organocatalytic Reactions.

Stereocontrolled formation of carbon-carbon and carbon-heteroatom bonds through asymmetric organocatalysis is a formidable challenge for modern synthetic chemistry. Among the most significant contributions to this field are the transformations involving the use of acetaldehyde or α-heteroatom-substituted acetaldehydes for constructing valuable synthons (e.g., amino acid derivatives and hydroxycarbonyl). In this Minireview, versatile (enantioselective) organocatalytic transformations are discussed.

The effect of low oxygen conditions on biogeochemical cycling of nutrients in a shallow seasonally stratified bay in southeast Korea (Jinhae Bay).

The formation and distribution of oxygen-deficient water mass (ODW) in Jinhae Bay exhibited seasonal patterns similar to those of the summer thermocline, indicating a close mutual relationship, and the influence of ODW formation conditions appeared prominently in the bottom water. The principal factors analysis indicate that dissolved oxygen and NO2 in the bottom water during the time of ODW formation were highly correlated with NH3 and dissolved inorganic phosphorus. The findings clearly illustrate the effects on ODW of seasonal physical and chemical changes. ODW that formed in the bottom water of Jinhae Bay during summer produced high concentrations of nutrients in the bottom water; since the growth of phytoplankton was limited by the strong stratification and low concentrations of dissolved oxygen (<3mg/L) in the bottom layer, these nutrients (especially NH3 and DIP) were retained and accumulated, serving as a major source of nutrients during the dry winter.

Isolation and characterization of a novel bacterial strain Shewanella marinisediminis sp. nov. from deep-sea sediments.

A new bacterial strain designated DH39T was isolated from marine sediment collected from the East Sea, Korea. Phylogenetic analysis using the 16S rRNA gene sequence revealed that strain DH39(T) clustered with the genus Shewanella and is closely related to Shewanella canadensis HAW-EB2(T), S. woodyi MS32(T), and S. sediminis HAW-EB3(T) with 98.1, 97.8, and 97.6% sequence similarities, respectively. The isolated bacterium was Gram-negative, rod-shaped, and aerobic. Its temperature range for growth was 4-30 degrees C. The predominant fatty acids were 16:1omega7, 17:1omega8, 13:0-i, 16:0, and 15:0-i. The DNA G+C content was 45.0 mol%. DNA-DNA hybridization analysis showed that DNA-DNA relatedness values in the 165 rRNA phylogenetic tree of strain DH39(T) and its nearest neighbors S. hanedai and S. sediminis were 52.9 and 58.7%. Phylogenetic evidence and phenotypic characteristics suggest strain DH39(T) constitutes a novel Shewanella species. Therefore, we propose Shewanella marinisediminis sp. nov., with DH39(T) (KCCM 42936(T) = NCCB 100311(T)) as the type strain.

N-heterocyclic carbene-catalysed intermolecular Stetter reactions of acetaldehyde.

A facile method for the intermolecular Stetter reaction of various Michael acceptors with acetaldehyde as a biomimetic acylanion source was realized using N-heterocyclic carbene catalysis. This catalytic system has also been applied to the enantioselective Stetter reaction and resulted in moderate to good enantioselectivities for the corresponding Stetter products.

Diurnal vertical migration of Cochlodinium polykrikoides during the red tide in Korean coastal sea waters.

The diurnal vertical migration of Cochlodinium polykrikoides (C. polykrikoides), which caused a red tide in the Korean coastal waters of the East Sea/Sea of Japan in September 2003, was examined by determining the time-dependent changes in the density of living cells in relation to the depth of the water column. The ascent of this species into the surface layer (depth of water 2 m) occurred during 1400-1500. The descent started at 1600 and a high distribution rate (86%) at 15-20 m was observed at 0300. During the ascent, the cells were widely distributed at each depth level from 0600 hr and at 0800-1100, the cells were primarily distributed in the middle layer (0-6 m). The concentration of dissolved inorganic nitrogen was generally < or = 2.86 micromol l(-1), but at 1400-1500, the concentration in the surface layer reduced to < or = 0.14 micromol l(-1). Moreover, the concentration gradually increased as the depth increased to > or = 5 m. These results showed that the nutrient-consumption rate associated with the proliferation of C. polykrikoides during a red tide is more influenced by the inorganic-nitrogen resources ratherthan the inorganic-phosphorus compounds.

Colwellia asteriadis sp. nov., a marine bacterium isolated from the starfish Asterias amurensis.

A marine bacterial strain, KMD 002T, was isolated from an Amur starfish, Asterias amurensis, collected in the East Sea of Korea. Strain KMD 002T was a Gram-negative, beige-pigmented, rod-shaped bacterium. The strain was capable of growth at relatively low temperatures (4-25 degrees C) and over a broad pH range (pH 4.0-10.0). The major fatty acids were C16:1omega7c and/or iso-C15:0 2-OH and C16:0 and the predominant isoprenoid quinone was Q-8. The DNA G+C content of strain KMD 002T was 40.3 mol%. Phylogenetic analysis using 16S rRNA gene sequences revealed that strain KMD 002T belonged to the genus Colwellia. However, various phenotypic properties as well as low 16S rRNA gene sequence similarities to members of the genus Colwellia (94.1-96.7%) suggested that strain KMD 002T is a representative of a novel species, for which the name Colwellia asteriadis sp. nov. is proposed. The type strain is KMD 002T (=KCCM 90077T =JCM 15608T).