Asymmetric Synthesis of Chiral Sulfimides through the O-Alkylation of Enantioenriched Sulfinamides and Addition of Carbon Nucleophiles

Chiral sulfimides, the aza-analogues of sulfoxides, are valuable compounds in organic synthesis and medicinal chemistry. Herein, we report an efficient method for preparing chiral sulfimides from easily available enantioenriched sulfinamides. The key step of this method is a stereospecific oxygen-selective alkylation of enantioenriched sulfinamides, which is accomplished by using isopropyl iodide, K₂CO₃, and DMPU. The resulting chiral sulfinimidate esters are transformed to chiral sulfimides by the nucleophilic addition of the Grignard reagents under simple conditions. This transformation enables access to the enantioenriched diaryl or dialkyl sulfimides bearing two similar carbon substituents, which are difficult to synthesize by previous methods.     

Palladium-catalyzed disilylation of o-quinodimethanes: synthesis of 9- and 10-membered disilacarbocycles

o-Quinodimethanes are efficiently inserted into a silicon-silicon bond of cyclic disilanes in the presence of a palladium-diphenyl-2-pyridylphosphine catalyst, giving 9- and 10-membered disilacarbocycles, that is, benzodisilonine and benzodisilecine.     

Determination of the antifungal agent voriconazole in human plasma using a simple column-switching high-performance liquid chromatography and its application to a pharmacokinetic study

A simple column-switching high performance liquid chromatographic (HPLC) method that does not require any complicated pretreatment has been developed to determine voriconazole in human plasma samples. An internal standard (IS) and borate buffer (pH 9.0) were added to plasma samples, which were then injected directly into the column-switching HPLC system using MAYI-ODS as a pre-column. The calibration curve for voriconazole showed good linearity in the range of 0.2-10 mug/ml in human plasma. The mean RSD (%) value of intra-day (n=6) and inter-day (n=5) precision were less than 5.4% and 8.2%, respectively. This system could make more than three hundred successive, accurate measurements when a washing step with ammonium acetate solution was added. This method was successfully applied to measure the therapeutic voriconazole level in patients' plasma, and was used in a study of voriconazole pharmacokinetics after oral administration.     

Ultraviolet photoelectron spectroscopy study of electronic states and deuterium adsorption on carbon nanowalls

Electronic structure of carbon nanowalls (CNW) was measured by ultraviolet photoelectron spectroscopy (UPS) in comparison with highly oriented pyrolitic graphite (HOPG). While the interlayer band of CNWs was observed at same energy of that in HOPG, the σ and π bands were observed as are in carbon nanotubes. Electronic effects by deuterium adsorption were investigated by combination of UPS and temperature programmed desorption (TPD) measurements. Deuterium adsorption preferably occurred in the boundary regions between crystallites in CNWs and enhanced the density of states associated with them.     

Looking glass inhibitors: scalable syntheses of DNJ,DMDP, and (3R)-3-hydroxy-l-bulgecinine from d-glucuronolactone and of l-DNJ,l-DMDP,and (3S)-3-hydroxy-d-bulgecinine from l-glucuronolactone. DMDP inhibits β-glucosidases and β-galactosidases whereas l-DMDP is a potent and specific inhibitor of α-glucosidases

A convenient large-scale synthesis of 1-deoxynojirimyin (DNJ) from d-glucuronolactone involves introduction of azide at C-5 with retention of configuration to give 5-azido-5-deoxy-1,2-O-isopropylidene-α-d-glucofuranose as a key intermediate in an overall yield of up to 72%; the same intermediate can be transformed into DMDP [(2R,3R,4R,5R)-2,5-bis(hydroxymethyl)pyrrolidine-3,4-diol] and (3R)-3-hydroxy-l-bulgecinine [(2S,3R,4R,5R)-3,4-dihydroxy-5-hydroxymethyl-l-proline]. l-Glucuronolactone, a readily available l-sugar chiron, may similarly be used to access the enantiomers l-DNJ, l-DMDP, and (3S)-3-hydroxy-d-bulgecinine. A comparison of glycosidase inhibition by DMDP (an inhibitor of β-glucosidases and β-galactosidases) and l-DMDP (a potent and specific α-glucosidase inhibitor) with the corresponding enantiomeric hydroxybulgecinines is reported; DMDP and (3R)-3-hydroxy-l-bulgecinine show weak inhibition of glycogen phosphorylase.     

Diastereoselective amidoallylation of glyoxylic acid with chiral tert-butanesulfinamide and allylboronic acid pinacol esters: efficient synthesis of optically active γ,δ-unsaturated α-amino acids

A convenient synthesis of δ,γ-unsaturated amino acids has been developed. After a mixture of (R)-tert-butanesulfinamide and glyoxylic acid with molecular sieves in CH₂Cl₂ was stirred for 42 h at room temperature, allylboronic acid pinacol ester was added to the mixture to give (R)-2-((R)-tert-butanesulfinamido)pent-4-enoic acid with high diastereoselectivity. The corresponding reaction of (Z)-crotylboronic acid pinacol ester produced no product; however, that of (E)-crotylboronic acid pinacol ester produced (2R,3S)-2-((R)-tert-butylsulfinamido)-3-methylpent-4-enoic acid with excellent diastereoselectivity.     

Gold(I)-catalyzed regioselective inter-/intramolecular addition cascade of di- and triynes for direct construction of substituted naphthalenes

The gold-catalyzed cascade intermolecular addition-intramolecular carbocyclization reaction of dialkynylbenzenes was developed. In this reaction, regioselective addition of an external nucleophile toward the terminal alkyne and subsequent 6-endo-dig cyclization proceeded to give the 1,3-disubstituted naphthalenes in good yields. The direct synthesis of disubstituted chrysenes via a gold-catalyzed addition and double cyclization cascade using a triyne-type substrate was also achieved.     

X-ray diffraction of protein crystal grown in a nano-liter scale droplet in a microchannel and evaluation of its applicability

We describe the technical aspects of the in-situ X-ray diffraction of a protein crystal prepared by a nanodroplet-based crystallization method. We were able to obtain diffraction patterns from a crystal grown in a capillary without any manipulation. Especially in our experimental approach, the crystals that moved to the nanodroplet interface were fixed strongly enough to carry out X-ray diffraction measurements that could be attributed to the high surface tension of the nanodroplet. The crystal was damaged by an indirect action of the X-rays because our in-situ X-ray diffraction measurement was carried out in the liquid phase without freezing the crystal; however, the obtained several diffraction patterns were of sufficiently fine quality for the crystal structure factors to be generated. We consider the technical examination presented in this paper to represent a seamless coupling of crystallization to X-ray analysis.     

Alumina cryogels with superior thermal stability for catalyst supports

Alumina cryogels were synthesized from a colloidal boehmite sol through a sol–gel processing and subsequent freeze drying, and thermal stability was examined by comparison to that of the corresponding xerogel, precipitate and commercial alumina. N₂ adsorption, X-ray powder diffraction and transmittance electron micrography observations revealed that the stability was higher for the cryogel than for others in particular at temperatures above 1,000 °C. The higher stability was ascribed to the fine and uniform primary particles with fibrous shapes formed by the sol–gel technique and furthermore to the suppression of aggregation of the primary particles owing to the subsequent freeze drying. It was also found that aluminum sec-butoxide employed as a precursor for the preparation of boehmite sol was preferable compared to aluminum iso-propoxide.