Iridium-catalyzed Oppenauer oxidations of primary alcohols using acetone or 2-butanone as oxidant

The first Oppenauer oxidation of primary alcohols with acetone or 2-butanone by an amino alcohol-based Ir bifunctional catalyst was accomplished. The reaction proceeds with 1 mol % catalyst in acetone or 2-butanone at 30-80 degrees C to give the corresponding aldehydes in 33-96% yield.     

Imaging of (13)C-labeled glucose and sorbitol in bovine lens by (1)H-detected (13)C nuclear magnetic resonance spectroscopy

Bovine lenses were incubated in a solution containing [1-(13)C]glucose (50 mM) for 1, 2 and 4 days. Spectroscopic images of [1-(13)C]glucose and [1-(13)C]sorbitol were constructed using (1)H-detected gradient-enhanced heteronuclear multiple-quantum coherence (GE-HMQC) in a 2.0-tesla magnetic field. Accumulations of [1-(13)C]glucose and [1-(13)C]sorbitol were mainly observed at the periphery of the lens. Their distributions corresponded to the cortex. (1)H-detected (13)C nuclear magnetic resonance (NMR) spectroscopic imaging by GE-HMQC successfully demonstrated the distribution of [1-(13)C]glucose and [1-(13)C]sorbitol at the periphery of bovine lenses.     

A new measurement of 208Tl levels

A new determination for the levels of the nucleus ²⁰⁸Tl was performed by measuring the γ-rays following the β^--decay of ²⁰⁸Hg. Twenty-six γ-rays were assigned and three new levels of ²⁰⁸Tl at 1.728 MeV, 1.652 MeV and 1.362 MeV have been affirmed. A partial ²⁰⁸Hg decaying γ scheme was proposed. The experimental level structure was compared with a shell model calculation. Received: 12 August 2002 / Accepted: 19 December 2002 / Published online: 25 February 2003 RID="a" ID="a"e-mail: Li41zhang@yahoo.com Communicated by W. Henning     

Relationships between Changes in Oxygenation during Exercise and Recovery in Trained Athletes

The purpose of this study was to investigate the relationships of rate of deoxygenation determined using near-infrared spectroscopy (NIRS) during isometric contraction exercise (Rate_deoxy) with maximal muscle strength, muscle thickness and muscle oxidative capacity of knee extensors in eight well-trained male athletes. The subjects performed sustained isometric extension at 30% and 50% of the maximal voluntary contraction (MVC) load for 10s and 30 repetitive maximal isokinetic knee extensions. Rate_deoxy in the final 5s of 30% MVC was negatively correlated with maximal muscle strength, muscle thickness of knee extensors and the half-time of deoxygenation recovery (T1/2) determined by NIRS after 30 repetitive maximal isokinetic contractions, defined as muscle oxidative capacity. The results suggest that Rate_deoxy during submaximai isometric contraction reflects muscle aerobic capacity.     

Versatile synthons for optically pure alpha-amino aldehydes and alpha-amino acids: (+)- and (-)-4,5-dialkoxy-2-oxazolidinones

Both enantiomers of trans-5-benzyloxy-4-methoxy- (BMOx) and trans-4,5-dimethoxy-2-oxazolidinones (DMOx), which are readily accessible from simple 2-oxazolone heterocycles, represent good candidates for a new class of chiral synthons for use in the preparation of optically pure alpha-amino aldehydes and alpha-amino acids, respectively.     

Cubic phases of 4'-n-alkoxy-3'-nitrobiphenyl-4-carboxylic acids (ANBC-n)

The structure of the thermotropic cubic phases of 4'-ⁿ-alkoxy-3'-nitrobiphenyl-4-carboxylic acids (ANBC-ⁿ, where ⁿ indicates the number of carbon atoms in the alkoxy group) was studied by X-ray diffraction. For the homologues with ⁿ = 15, 16, 17, and 18, the cubic phase was of an ^Ia3^d type, whereas the homologues with ⁿ = 19, 20, and 21 exhibited an ^Im3^m cubic structure; for these seven homologues the same type of cubic structure was observed both on heating and cooling. Further lengthening of the alkoxy chain to ⁿ = 22 and 26, however, gave two types of cubic structure in the cubic phase region on heating, one with ^Im3^m symmetry in the low temperature region and the other with ^Ia3^d symmetry in the high temperature region. On cooling, the two homologues exhibited the ^Ia3^d cubic structure only. This is the first example in the cubic phase region of a series of homologues containing two types of structure, dependent on temperature and ⁿ. Such a complicated phase diagram in the cubic region is clearly understood qualitatively in terms of Gibbs free energy-temperature diagrams. The dependence of structural parameters such as the cubic lattice constant on the alkoxy chain length ⁿ are also presented and discussed.     

Charge-transfer bands observed with the intermolecular hydrogen-bonded systems between acetic acid and some aliphatic amines

Near and vacuum uv absorption spectra were measured for aliphatic amine-acetic acid systems in the gaseous state and in solution at room temperature. Equilibrium constants for complex formation were determined, and new absorption bands due to the hydrogen-bonded species between amines and acetic acid were observed near 170 nm in n-heptane and in acetonitrile, and at ～165 nm in the vapor phase. The new band of the triethylamine (TEA)-acetic acid system shifts to longer wavelengths in the order: in the vapor phase → in n-heptane → in acetonitrile. This is the reverse of the shift of the $\text{n-σ}{}^1$ band of TEA. The new band positions of the amine-acetic acid systems correlate to the ionization potentials of the amines. These facts together with theoretical results by the composite molecule method lead us to the interpretation that the new bands are the charge-transfer band characteristic of the hydrogen-bonded species.     

Paeoniflorigenone,a new monoterpene from paeony roots

Paeoniflorigenone (1), a new monoterpene which produces a neuromuscular-blocking effect in mice, was isolated from paeony roots and its structure was elucidated.