Efficient preparation of enantiomerically pure cyclic aminoalditols,total synthesis of 1-deoxynojirimycin and 1-deoxymannojirimycyn

Expeditious new syntheses of the title compounds, which are potent glycosidase inhibitors, have been developed based on a high-yield, ring-forming aminomecuration.     

Synthesis of 2S-carboxy-3R,4R,5S-trihydroxypiperidine; a naturally occurring inhibitor of β-D-glucuronidase

The glucuronic acid analog 5 of 1-deoxynojirimycin has been synthesized in good overall yield from D-glucose.     

The effects of sample preparation methods on the variability of the electrospray ionization response for model drug compounds

A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd.     

Gamma-ray spectroscopy with relativistic exotic heavy-ions

Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors (segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed.     

Efficient syntheses of 1,2,3,4,4a,5-hexahydro-pyrazino[2,1-c][1,4]benzothiazine-6,6-dioxide

Expeditious routes to 1,2,3,4,4a,5-hexahydro-pyrazino[2,1-c][1,4]benzothiazine-6,6-dioxide, a methylenesulfone-constrained arylpiperazine, have been developed. The key step forms the tricyclic system in a cascade of reactions via a 1,4-addition, nitrogen alkylation, and aromatic substitution sequence.     

Percolative transport in the vicinity of charge-order ferromagnetic transition in a hole-doped manganite

We report measurements of non-linear charge transport in epitaxial (La_1−x Pr _x )_0.7Ca_0.3MnO₃ thin films fabricated on (100) oriented SrTiO₃ single crystals by pulsed laser deposition. The end members of this series, namely Pr_0.7Ca_0.3MnO₃ and La_0.7Ca_0.3MnO₃ are canonical charge-ordered (CO) and ferromagnetic manganites, respectively. The onset of the CO state in Pr_0.7Ca_0.3MnO₃ is manifested by a pronounced insulating behavior below ∼ 200 K. The CO state remains stable even when a large (∼ 2×10⁵ V/cm) electric field is applied across the thin film samples. However, on substitution of Pr with La, a crossover from the highly resistive CO state to a state of metallic character is observed at relatively low electric fields. The current-voltage characteristics of the samples at low temperatures show hysteretic and history dependent effects. The electric field driven charge transport in the system is modelled on the basis of an inhomogeneous medium consisting of ferromagnetic metallic clusters dispersed in a CO background.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

Thermal Cleavage of Oxazolidine-4,5-diones to Imines: A Short Synthesis of 3,4-Dihydro-3,3-dimethyl-7-trifluoromethylisoquinoline-2-oxide

A series of oxazolidine-4,5-diones 2 was thermally cleaved to cyclic imines 3 in excellent yield. This reaction was utilized in an efficient synthesis of a 3,4-dihydroisoquinoline-based nitrone 1b.     

Second quantization and coefficients of fractional parentage

The coefficients of fractional parentage (CFP ), treated by tradition as antisymmetrizing multipliers, do not exist as such in the second-quantization representation, because, therein, by definition, there is nothing to antisymmetrize. This by no way means that the above-mentioned representation is less relevant in theoretical atomic spectroscopy than is any other one. On the contrary, all the well-known mathematical apparatus is still successfully applied, alongside with numerous new useful features. Moreover, the analysis presented here yields some results not so obvious from the point of view of the coordinate representation, namely, the consequent application of the second-quantization representation led us to an expansion of many-shell wave functions employing analogs of many-shell CFP , which appeared to be considerably simpler than the traditional CFP expansion. Also, a generalization of Redmond's formula for the case of many-shell CFP and a straightforward method of deriving summation rules for products of CFP are clear in the second-quantization representation and are sketched here. © 1994 John Wiley & Sons, Inc.