Flux and fluence dependence of disorder produced during implantation of 11B in silicon

The flux and fluence dependence of disorder produced in silicon during the implantation of ¹¹B has been investigated at room temperature, -50°C. and -120°C. Implantations were carried out with 200 keV ¹¹B ions using current densities in the range from 0.06μA/cm² to 15μA/cm², and the disorder monitored by measuring the energy spectra of backscattered protons which were incident on the sample at 450 keV parallel to a (110) axis. Significant differences in the dependence of the disorder on ¹¹B flux and fluence were observed between the implantations performed at room temperature and those carried out at the two lower temperatures.     

An Efficient Process for the Synthesis of Renin Inhibitor,ABT-517

An efficient process for the preparation of renin inhibitor, ABT-517 is described. The process avoids solvent extractions or chromatographic purifications and is used on multi-kilogram scale.     

Charge Transfer Complexes of 1-Naphthylmethyl Cotton Cellulose

A cotton cellulose derivative that forms charge-transfer complexes was prepared in yarn form. A charge-transfer complex is composed of two partners, one referred to as the donor and the other as an acceptor of electrical charge. In the present investigation, a donor was chemically bound to the cotton. It was shown that the modified donor cellulose adsorbs various acceptors from solution. Celluloses possessing donor or acceptor moieties are potentially useful as chromatographic agents and also in medicinal chemistry where a controlled release of a chemical agent is desired.     

A Total Synthesis of (±)-Trichodiene

Trichodiene (1), a sesquiterpene hydrocarbon, was isolated from the extract of mycelium of Trichothecium roseum. The structure of trichodiene (1) was elucidated by Nozoe and Machida in 1970 via degradation and spectroscopy.¹ Trichodiene (1) has been shown to be the biogenetic precursor of the trichothecane family of sesquiterpenoids as characterized by the cytotoxic fungal metabolite (-)-trichodermin (2).^2,3 The structure and absolute stereochemistry of (-)-trichodermin (2) were determined by X-ray diffraction and, therefore, the structure and absolute stereochemistry of trichodiene (1) are now firmly established.⁴ We wish to report a total synthesis of (±)-trichodiene (1) via previously reported lactone 3.^5,6     

Sterically congested macrobicycles with heteroatomic bridgehead functionality

A series of cyclophanes composed of two triarylelement caps linked by two-atom bridges has been synthesized. The bridgehead functional groups include phosphines in combination with amines, hydrosilanes, methylsilanes, and ethoxysilanes. Computational studies accurately predicted that when the bridgehead substituents are small (lone pairs or protons), an in_,in bridgehead stereochemistry is strongly favored, but larger bridgehead substituents favor the formations of in_,out stereoisomers. The X-ray structures, spectra, and reactivity of these compounds are discussed, as well as the resolution of one of the cyclophanes into pure enantiomers.     

Synthesis and X-Ray Crystal Structure of Methyl D,L-Desmeihyl-Holantosaminide

4-Acetamido-2,4,6-trideoxy-D,L-arabino-hexopyranose, a desmethyl analog of N-acetyl-L-hoTantosamine, the glycosidic residue of the cardenolide HoTarosine A and holantosines C and D, has been prepared via a novel intramolecular rearrangement of an amino alcohol and has been characterized by single-crystal X-ray diffraction.     

The Reaction of Methyl 2,4,6-Tri-0-benzoyl-3-0-benzyl-β-D-galactopyranoside with 1,1-Dichloromethyl Methyl Ether

When methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-β-D-galacto-pyranoside (JO is treated in purified chloroform at 55-60′ with excess of dichloromethyl methyl ether in the presence of a catalytic amount of freshly fused zinc chloride for 1 h the corresponding α-glycosyl chloride 2 can be isolated by column chromatography in 75-80% yield. Compound 2 is an important intermediate in the synthesis of oligosaccharides containing a glycosyl-3-0-galactosyl sequence. Under the described reaction conditions the conversion 1 - 2 is accompanied by a slow anomerisation of 1 to give methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-α-D-galactopyranoside. Prolonged treatment of 2 with the used excess of the reagent results in complete debenzylation of the substrate and the conversion of the putative 2,4,6-tri-O-benzoyl-α-D-galactopyranosyl chloride into the corresponding 3-0-formyl and 3-0-dichloromethyl derivatives.     

Catalyst free,base free microwave irradiated synthesis of aryl nitrites from potassium aryltrifluoroborates and bismuth nitrate

A mixture of bismuth nitrate pentahydrate and potassium aryltrifluoroborate in toluene under microwave heating at 120 °C for 20 min provides an interesting and mild reaction protocol for the synthesis of aryl nitrite. The conversion to aryl nitrites from aryltrifluoroborates without transition metal catalyst and base in high yields is remarkable.     

Development and validation of a hydrophilic interaction liquid chromatography with tandem mass spectrometry method for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine

A sensitive hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method was developed and validated for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine. The method is highly sensitive and specific with good precision and accuracy. In plasma the limit of detection and limit of quantification are 0.03 and 0.1 ng/mL, respectively, for both analytes. In urine the limit of detection and limit of quantification are 0.3 and 1 ng/mL, respectively, for both analytes. The suitability of the method for doping control analysis in equine species is demonstrated by analyzing postadministration samples collected after a single intravenous administration of 50 mg etilefrine to a standardbred mare. Etilefrine was detected up to 120 h in urine and up to 48 h in plasma. Etilefrine is highly conjugated in equine urine whereas it exists in the free form in equine plasma. Therefore, enzyme hydrolysis prior to sample preparation is recommended for the detection and quantification of etilefrine and oxilofrine in equine urine.