Non-aqueous,reversed-phase,high-performance,thin-layer chromatography and column liquid chromatography of metal complexes of porphine

Summary The chromatographic mobility of 21H, 23H-porphine and its Ni(II), Cu(II), Zn(II) and Pd(II) complexes were investigated by high-performance thin-layer chromatography on an octadecyl-bonded, silica gel plate with various polar organic solvents including alcohols, acetonitrile, dimethylsulfoxide and propylenecarbonate. The mobility generally decreases according to the central metal ion of the complex as follows: Zn(II)>(free porphine)>Ni(II)>Pd(II)>Cu(II). Methanol is a good choice of solvent for the separation of these metal porphine complexes. Successful separation of porphine and the four metal complexes is accomplished within 13 min on a LiChrosorb RP-18 column with methanol eluent.     

Synthesis of bis(alk-3-en-1-ynyl)benzene with either E- or Z-configuration via a one-pot three-component coupling reaction and its optical properties

A convenient, efficient and stereoselective synthesis of a range of bis(alk-3-en-1-ynyl)benzenes with E- and Z-configuration is described. The protocol involves Cu-mediated cross-coupling reaction of (E)- and (Z)-alk-1-enyldisiamylboranes with (trimethylsilyl)ethynyl bromide and Pd/Cu-catalyzed cross-coupling reaction with diiodobenzene. The sequential cross-coupling reaction proceeds readily under extremely mild conditions in a one-pot manner to afford bis(alk-3-en-1-ynyl)benzenes in good to excellent yields. The optical properties of the products are also described.     

Gamma-ray spectra of 201Tl-radiopharmaceuticals with a scintillation camera--crosstalk of contaminating nuclides of 200Tl and/or 202Tl onto 201Tl-photopeaks

In cardiac imaging with 201Tl, the collimator for low energy high resolution is generally used, and also the energy window, which is set on the spectral display of a pulse height analyzer of a scintillation camera, is chosen 70 +/- 12.5 keV. The purpose of this study is to discuss those conditions in 201Tl imaging with the scintillation camera. Two types of collimators for HR (high resolution) and ME (medium energy) were used in this experiment, and we measured the pulse height spectra of 201TlCl radiopharmaceuticals in air and in a cuboid phantom, connecting a multi-channel pulse height analyzer to the scintillation camera. As a result of measuring of the pulse height spectra, two different energies of gamma rays which are not supposed to emit from 201Tl nuclide were observed, and we also identified the presence of a small amount of 202Tl (with 439 keV) and/or 200Tl (with 368 keV) from their half-life measurements. Thus, the use of the HR-collimator with 201Tl imaging is not suitable, because the shielding effects of its septa is poor to 439 keV gamma-rays, and the scattered radiation produced by the Compton interaction contributes to the principal photopeak on the pulse height spectrum. Here, we recommend the use ME-collimator instead of the HR-one, and of the window width of 76 +/- 25 keV for increasing the count rate.     

Function of the Reaction Center of Green Sulfur Bacteria

The reaction center (RC) of green sulfur bacteria belongs to the Fe-S type RC, as do the photosystem I of oxygenic photosynthetic organisms and the RC of heliobacteria. The core parts of the green sulfur bacterial and the heliobacterial RC are assumed to be homodimeric, in contrast to those of purple bacteria, photosystem I and photosystem II. This paper describes recent advances in the study of the function of the green sulfur bacterial RC.     

The formation of clathrate-like hydrates of tetrabutylammonium halogenated carboxylates

The solid-liquid phase diagrams of binary mixtures of tetrabutylammonium halogenated carboxylates with water were examined in order to confirm the formation of clathrate-like hydrates. It was found that, among thirteen carboxylates examined, four carboxylates having CH₂FCOO^–, CHF₂COO^–, CF₃COO^–, and CH₂ClCOO^–, formed a hydrate with hydration numbers around 30 and seven carboxylates having CHCl₂COO^–, CCl₃COO^–, CH₂BrCOO^–, CHBr₂COO^–, CBr₃COO^–, CH₃CHClCOO^–, and CH₃CHBrCOO^– formed a hydrate with hydration numbers around 23. The latter hydrate has not been reported earlier. The melting points of these newly found hydrates were fairly high: they lie between 10 and 16°C. The effect of Cl and Br atoms attached to the carbon atom of the-position of a carboxylate anion both on the type of hydrate formed and on its stability was greatly different from that of a CH₃ group attached to the same position of the carboxylate anion.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

Control of charge-transfer-induced spin transition temperature on cobalt-iron Prussian blue analogues

The electronic and spin states of a series of Co-Fe Prussian blue analogues containing Na(+) ion in the lattice, Na(x)()Co(y)()Fe(CN)(6) x zH(2)O, strongly depended on the atomic composition ratio of Co to Fe (Co/Fe) and temperature. Compounds of Co/Fe = 1.5 and 1.15 consisted mostly of the Fe(III)(t(2g)(5)e(g)(0), LS, S = 1/2)-CN-Co(II)(t(2g)(5)e(g)(2), HS, S = 3/2) site and the Fe(II)(t(2g)(6)e(g)(0), LS, S = 0)-CN-Co(III)(t(2g)(6)e(g)(0), LS, S = 0) site, respectively, over the entire temperature region from 5 to 350 K. Conversely, compounds of Co/Fe = 1.37, 1.32, and 1.26 showed a change in their electronic and spin states depending on the temperature. These compounds consisted mainly of the Fe(III)-CN-Co(II) site (HT phase) around room temperature but turned to the state consisting mainly of the Fe(II)-CN-Co(III) site (LT phase) at low temperatures. This charge-transfer-induced spin transition (CTIST) phenomenon occurred reversibly with a large thermal hysteresis of about 40 K. The CTIST temperature (T(1/2) = (T(1/2) descending + T(1/2) ascending)/2) increased from 200 to 280 K with decreasing Co/Fe from 1.37 to 1.26. Furthermore, by light illumination at 5 K, the LT phase of compounds of Co/Fe = 1.37, 1.32, and 1.26 was converted to the HT phase, and the relaxation temperature from this photoproduced HT phase also strongly depended on the Co/Fe ratio; 145 K for Co/Fe = 1.37, 125 K for Co/Fe = 1.32, and 110 K for Co/Fe = 1.26. All these phenomena are explained by a simple model using potential energy curves of the LT and HT phases. The energy difference of two phases is determined by the ligand field strength around Co(II) ions, which can be controlled by Co/Fe.     

Control of separation selectivity in micellar electrokinetic chromatography by modification of the micellar phase with solubilized organic compounds

On the basis of the data on the distribution of various neutral solutes between sodium dodecyl sulfate (SDS) micelles and water, the control of separation selectivity in micellar electrokinetic chromatography (MEKC) by modification of the micellar phase with organic additives has been proposed and applied to the separation of simple model compounds. It was found that the distribution constants between the micelles and water (K_d,mc), which were determined by means of MEKC, of the solutes possessing hydrophilic functional groups are much larger than those between heptane and water (K_d,hep), whereas the K_d,mc values of the solutes possessing no hydropholic groups are comparable to their K_d,hep values. This indicates that the former solutes are preferentially solubilized in the Stern layer of the micelles and that the latter are located in the hydrocarbon core. In MEKC separations of aromatic compounds and metal acetylacetonates, considerable changes in separation selectivity were caused by the addition of compounds possessing both hydrophilic functional groups such as alcohols, phenol and ketones to the SDS micellar solution. The variations of the retention factors of the analytes could be explained in terms of saturation of the solubilization sites in the Stern layer with the modifiers, specific interaction of the modifiers with the analytes via hydrogen bonding in the micelles, and expansion of the core volume with the hydrocarbon parts of the modifiers. Such effects of the micellar modification could improve the resolution as well as the selectivity of MEKC separations.     

Enantioselective addition of ketene silyl acetals to nitrones catalyzed by chiral titanium complexes. Synthesis of optically active beta-amino acids

A chiral titanium complex, Ti(O-i-Pr)(4)/BINOL/tert-butylcatechol, catalyzes enantioselective addition reaction of ketene silyl acetals to nitrones to give optically active beta-amino acid derivatives which are biologically active compounds and useful synthetic intermediates of natural products and pharmaceuticals such as beta-lactam antibiotics. The combined process of catalytic oxidation of secondary amines and enantioselective carbon-carbon bond formation of nitrones thus obtained with ketene silyl acetals provides a useful two-step method for the synthesis of optically active beta-amino acid derivatives and related nitrogen compounds.     

A synthesis of chiral 1,1,3-trisubstituted 1,2,3,4-tetrahydro-beta-carbolines by the Pictet-Spengler reaction of tryptophan and ketones: conversion of (1R,3S)-diastereomers into their (1S,3S)-counterparts by scission of the C(1)-N(2) bond

The Pictet-Spengler cyclization of the imines (3) prepared by the condensation of L-tryptophan methyl ester (1) and aryl methyl ketones (2), using titanium(IV) isopropoxide as an iminating reagent, quantitatively proceeded, when treated with trifluoroacetic acid (TFA) or formic acid, to provide two diastereomers, that is (1S,3S)-1-aryl-3-isopropoxycarbonyl-1-methyl-1,2,3,4-tetrahydro-beta-carbolines (4) and their (1R,3S)-diastereomers (5), of which the diastereomer ratios varied from 1 to 5 depending on the reaction conditions. The (1R,3S)-diastereomers (5) are thermodynamically more stable than their (1S,3S)-congeners (4), as shown by equilibration experiments in TFA. The conversion of 4 to 5 (also 5 to 4) should occur under acidic conditions by cleavage of the C(1)-N(2) bond with complete retention of configuration at the C-3 chiral center. The low diastereo-selectivity observed in the Pictet-Spengler reaction of 1 and 2 is concluded to be a stereochemical outcome under conditions of kinetic control (lower temperature, shorter reaction time), while the high diastereo selectivity with preferential formation of the more stable isomer (5) is the result of thermodynamically controlled experiments (higher temperature, longer reaction time).