Crystal Structure and Solid State 13C Nmr Analysis of Methyl 3,4,6-Tri-O-Acetyl-2-Deoxy-2-(3-Phenylureido)-β-D-Glucopyranoside

ABSTRACT

The X-ray diffraction analysis of methyl 3,4,6-tri-O-acetyl-2-deoxy-(3-phenylureido)-β-D-glucopyranoside was performed and showed that the molecules are associated by two NHz.O=C hydrogen bonds. One molecule with disorder of an acetyl group at C-4 was found in the asymmetric crystal unit. The signals in ¹³C CPMAS NMR spectrum are duplicated indicating that local symmetry is lower than those of the crystal.     

How Points Escape to Infinity Under Exponential Maps

We investigate the finer fractal structure of the set of pointsescaping to infinity under iteration of an arbitrary exponentialmap. Providing exact formulas, we show how sensitively the Hausdorffdimension depends on the rate of growth of canonical Devaney–Krychcodes.     

Synthesis of the enantiomers of the dual function 2‐nitroimidazole radiation sensitizer RB 6145

Short, efficient pathways are described for the synthesis of racemic 2‐nitroimidazole radiation sensitizer RB‐6145 ( 2a ) and each of its corresponding (R)‐ and (S)‐enantiomers ( 2b and 2c , respectively). The synthesis of each enantiomer commences with the appropriate chiral epichlorohydrin and utilizes a novel application of 3‐trimethylsilyl‐2‐oxazolidinone ( 3b ) as a mild, safe surrogate for highly toxic aziridine. The synthesis of the (R)‐enantiomer ( 2b ) has been successfully scaled up to provide multi‐kilo quantities of material for early stage preclinical evaluation.     

Infrared study of hydrogen bonds involving N-heterocyclic bases and phenols

The hydrogen bond complexes between phenols and N-heteroaromatic bases 2,4,6-tri(2-pyridyl)-1,3,5-triazine, 2,2′,2′-terpyridine, quinoxaline, pyrido[2,3-b]pyrazine, pyzazino [2,3f]quinoxaline and 5-nitrozphenanthroline are investigated by infrared spectroscopy in 1,2-dichloroethane. The stability constants of the complexes involving N-heteroaromatic bases characterized by tow vicinal nitrogen atoms having lone pairs pointing to each other are higher than predicted from their basicity. Possible differences between protonation and hydrogen bond formation are discussed. Nheteroaromatic bases such as tri(2-pyridyl)-1,3,5-triazine or phenanthrolines cannot be considered as proton sponges but their behaviour is intermediate between that of the classical heteroaromatic bases and the proton sponges.     

Anticancer anilinoacridines. A process synthesis of the disubstituted amsacrine analog CI-921

An improved process for the synthesis of bulk quantities of the clinical amsacrine analog CI-921 is reported. Described also are detailed analytical and spectroscopic data for this agent.     

Multivariate estimation between mid and near-infrared spectra of hexafluoroisopropanol-water mixtures.

Multivariate regression based on partial least squares (PLS2) was applied to estimating one spectral dataset from another set having an intrinsic relationship with each other. An estimation was successfully carried out between mid-infrared (IR) spectra in the range of 2980 - 3800 cm(-1) and that of near-infrared (NIR) spectra in the range of 6000 - 7500 cm(-1) for hexafluoroisopropanol (HFIP)-water mixtures. The result demonstrates that, after building a suitable regression model, not only NIR spectra, but also well-resolved IR spectra of HFIP-water mixture can be estimated properly in this way. The use of IR and NIR spectroscopy together with PLS2 regression will not only alleviate laborious and costly measurements, but also open a way to provide easier assignments of generally weak and highly overlapped NIR spectral bands.     

Photoluminescence characterization of air exposed AlGaAs surface and passivated ex situ by ultrathin silicon interface control layer

Using the photoluminescence surface state spectroscopy (PLS³) technique, attempts were made to determine the surface state density (N_ss) distribution on Al_xGa_1−xAs (x≈0.3) surfaces passivated by the Si interface control layer (ICL) technique. Air-exposed AlGaAs epitaxial wafers which are technologically important for fabrication of various devices were passivated ex situ by forming a SiO₂/Si₃N₄/Si ICL/AlGaAs structure after the HCl treatment and their photoluminescence behavior was investigated in detail. The result of the PLS³ analysis indicated that Si ICL-based passivation reduces the minimum interface state density value down to 10¹⁰ cm⁻² eV⁻¹ range. Some indication was also obtained that further improvements are possible by using electron cyclotron resonance (ECR)-enhanced N₂ plasma for Si₃N₄/Si ICL interface formation.     

An improved synthesis of anticancer benzothiopyranoindazoles. An efficient large-scale β-aminoethylation procedure

Improved processes for the synthesis of bulk quantities of the benzothiopyranoindazole clinical agent CI-958 and A-ring congeners is reported. The process chosen for scale-up operations achieves β-aminoethylation of an anilino precursor via a three-step sequence (acylation, reduction, deprotection) starting from N-(trityl)glycine. Detailed analytical data are reported for the target compounds and most intermediates, and detailed spectroscopy is given for CI-958.     

1H n.m.r. conformational studies of glycyl-L-phenylalanine and L-phenylalanyl-glycine dipeptides and their complexes with palladium (II)

The conformations of Gly-Phe and Phe-Gly dipeptides and those of their complexes with the Pd(II) ion has been established by means of ¹H n.m.r. spectra over various pH ranges. In the most stable rotamer of both dipeptides the bulkiest groups, i.e. carboxylate (or carbonyl) and the aromatic ring, are in trans position to each other. In the 1:1 molar ratio complexes, the dipeptides are the tridentate ligands within the 3–10 pH region. In the predominant conformer the aromatic ring lies over the complex plane, which suggests its interaction with the metal ion. At pH above 13, the carboxyl group becomes non-coordinated. The dipeptides are then bidentate and the most stable rotamers are the same as those found for the metal-free ligands, i.e. the carboxyl or carbonyl group is in the trans position to the aromatic ring. The glycine chelate ring in the Pd(II) Gly-Phe complex is planar up to pH 10 and its distortion from planarity follows when the ligand becomes bidentate.     

Anticancer anthrapyrazoles. Improved syntheses of clinical agents CI-937, CI-941, and piroxantrone hydrochloride

Improved processes for the synthesis of bulk quantities of the anthrapyrazole clinical agents CI-937, CI-941, and piroxantrone hydrochloride are reported. Reported also are detailed analytical and spectroscopic data for these agents and intermediates of the synthetic sequences.