Isolation and characterization of a novel multibridged tetradentate dianionic form of pyridoxic acid. Crystal structure of tetranuclear [Cu4(PAA)2(Bipyam)4(H2O)2Cl2](NO3)2·CH3OH·10H2O

The X-ray analysis of the tetranuclear copper(II) complex formed from pyridoxic acid and 2,2′-dipyridylamine reveals a novel metal binding mode of pyridoxic acid as a multibridged tetradentate dianion. Here the pyridoxic acid moiety uses all possible sites except the pyridine nitrogen for metal coordination.

Structural Investigations on Poly(4-hydroxy-L-proline). 2. Physicochemical Studies

We report experimental studies which confirm our prediction, namely that the ordered structure of poly(hydroxypro1ine) in solution corresponds to a left-handed helical structure with intrachain hydrogen bonds. The CD studies show that the poly(hydroxypro1ine) molecule has essentially the same conformation in aqueous solution and in the film obtained subsequently by evaporation. X-ray diffraction patterns of the sample in this form (B form) have been recorded at different relative humidities. The patterns recorded at relative humidities over 66% can be interpreted in terms of a helical structure with intrachain hydrogen bonds. These results lead us to conclude that the ordered conformation of poly(hydroxypro1ine) in solution is form B and not form A. This offers a simple explanation for the greater stability of the poly(hydroxypro1ine) helix in solution as compared to the poly(pro1ine) form I1 helix and also for the absence of mutarotation for poly(hydroxypro1ine).

Structural Investigations on Poly(4-hydroxy-L-proline). 1. Theoretical Studies

Model building studies on poly(hydroxypro1ine) indicate that in addition to the well-known helical structure of form A, a left-handed helical structure with trans peptide units and with h = 2.86 A and n = 2.67 (i.e., 8 residues in 3 turns) is also possible. In this structure which is shown to be in agreement with X-ray data of the form B in the next paper, the y-hydroxyl group of an (i + 1)th Hyp residue is hydrogen bonded to the carbonyl oxygen of an (i - 1)th residue. The possibility of a structure with cis peptide units is ruled out. It is shown that both forms A and B are equally favorable from considerations of intramolecular energies. Since form B is further stabilized by intrachain hydrogen bonds, we believe that this is likely to be the ordered conformation for poly(hydroxypro1ine) in water.

Numerical estimation of hotspot temperatures in electrodes subjected to pulsed electron beam heating in vacuum

A numerical solution for the transient temperature distribution in a cylindrical disc heated on its top surface by a circular source is presented. A finite difference form of the governing equations is solved by the Alternating Direction Implicit (ADI) time marching scheme. This solution has direct applications in analyzing transient electron beam heating of target materials as encountered in the prebreakdown current enhancement and consequent breakdown in high voltage vacuum gaps stressed by alternating and pulsed voltages. The solution provides an estimate of the temperature for pulsed electron beam heating and the size of thermally activated microparticles originating from anode hot spots. The calculated results for a typical 45kV (a.c.) electron beam of radius 2.5 micron indicate that the temperature of such spots can reach melting point and could give rise to microparticles which could initiate breakdown.

Oxidation Of Spiroalcohols With 2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone (Ddq) .4. Structure Of A Novel Dioxepin Derivative

DDQ oxidation of the spiroalcohol 7a gives exclusively a compound to which the 13a-methyl-13aH-7a, 15-methano-15H-dinaphtho[2,1-b:2',1'-e][1,4]-dioxepin structure 8a has been assigned on the basis of two-dimensional homonuclear (H-1-H-1) and heteronuclear (H-1-C-13; FUCOUP) correlation spectroscopy experiments. Similar oxidation of spiroalcohols 7b-h gives the dioxepin derivatives 8b-h.

Silva Fennica Vol. 4. 1970.

Julkaistu Silva Fennica Vol. 5(1) -numeron liitteenä.

Reactivity Of Pph3 Toward Ruiiruiiicl(O2car)4 - Syntheses, Molecular-Structures, And Spectroscopic And Electrochemical Properties Of Ruiiruiii(Oh2)Cl(Mecn)(O2car)4(Pph3)2 And Ruii2(Oh2)(Mecn)2(O2car)4(Pph3)2

By the reaction of Ru2Cl(O2CAr)4 (1) and PPh3 in MeCN-H2O the diruthenium(II,III) and diruthenium(II) compounds of the type Ru2(OH2)Cl(MeCN)(O2CAr)4(PPh3)2 (2) and Ru2(OH2)(MeCN)2(O2CAr)4(PPh3)2 (3) were prepared and characterized by analytical, spectral, and electrochemical data (Ar is an aryl group, C6H4-p-X; X = H, OMe, Me, Cl, NO2). The molecular structure of Ru2(OH2)Cl(MeCN)(O2CC6H4-p-OMe)4(PPh3)2 was determined by X-ray crystallography. Crystal data are as follows: triclinic, P1BAR, a = 13.538 (5) angstrom, b = 15.650 (4) angstrom, c = 18.287 (7) angstrom, alpha = 101.39 (3)-degrees, beta = 105.99 (4)-degrees, gamma = 97.94 (3)-degrees, V = 3574 angstrom 3, Z = 2. The molecule is asymmetric, and the two ruthenium centers are clearly distinguishable. The Ru(III)-Ru(II), Ru(III)-(mu-OH2), and Ru(II)-(mu-OH2) distances and the Ru-(mu-OH2)-Ru angle in [{Ru(III)Cl(eta-1-O2CC6H4-p-OMe)(PPh3)}(mu-OH2)(mu-O2CC6H4-p-OMe)2{Ru(II)(MeCN)(eta-1-O2CC6H4-p-OMe)(PPh3)}] are 3.604 (1), 2.127 (8), and 2.141 (10) angstrom and 115.2 (5)-degrees, respectively. The compounds are paramagnetic and exhibit axial EPR spectra in the polycrystalline form. An intervalence transfer (IT) transition is observed in the range 900-960 nm in chloroform in these class II type trapped mixed-valence species 2. Compound 2 displays metal-centered one-electron reduction and oxidation processes near -0.4 and +0.6 V (vs SCE), respectively in CH2Cl2-TBAP. Compound 2 is unstable in solution phase and disproportionates to (mu-aquo)diruthenium(II) and (mu-oxo)diruthenium(III) complexes. The mechanistic aspects of the core conversion are discussed. The molecular structure of a diruthenium(II) compound, Ru2(OH2)(MeCN)2(O2CC6H4-p-NO2)4(PPh3)2.1.5CH2Cl2, was obtained by X-ray crystallography. The compound crystallizes in the space group P2(1)/c with a = 23.472 (6) angstrom, b = 14.303 (3) angstrom, c = 23.256 (7) angstrom, beta = 101.69 (2)-degrees, V = 7645 angstrom 3, and Z = 4. The Ru(II)-Ru(II) and two Ru(II)-(mu-OH2) distances and the Ru(II)-(mu-OH2)-Ru(II) angle in [{(PPh3)-(MeCN)(eta-1-O2CC6H4-p-NO2)Ru}2(mu-OH2)(mu-O2CC6H4-p-NO2)2] are 3.712 (1), 2.173 (9), and 2.162 (9) angstrom and 117.8 (4)-degrees, respectively. In both diruthenium(II,III) and diruthenium(II) compounds, each metal center has three facial ligands of varying pi-acidity and the aquo bridges are strongly hydrogen bonded with the eta-1-carboxylato facial ligands. The diruthenium(II) compounds are diamagnetic and exhibit characteristic H-1 NMR spectra in CDCl3. These compounds display two metal-centered one-electron oxidations near +0.3 and +1.0 V (vs SCE) in CH2Cl2-TBAP. The overall reaction between 1 and PPh3 in MeCN-H2O through the intermediacy of 2 is of the disproportionation type. The significant role of facial as well as bridging ligands in stabilizing the core structures is observed from electrochemical studies.

Wegener's granulomatosis in Finland in 1981-2000

Objectives: Wegener s granulomatosis (WG) is a vasculitis with a predilection for the airways and kidneys. An increasing incidence and improved prognosis of WG has been shown. The aim of this study was to evaluate the incidence, clinical presentation, diagnostic delay, risk of dialysis-dependent renal insufficiency and mortality of WG in 1981-2000. Patients and methods: Data was retrieved from the Finnish hospital discharge register and hospital case reports. Patients diagnosed with WG in 1981-2000 were included, and their demographic and clinical data recorded. The patients were crossed with the national kidney dialysis register and the national mortality statistics. Results: A total of 492 patients (243 ♂ , 249 ♀) were diagnosed at a mean age of 54 years (SD 18). The incidence increased from 1.9 to 9.3/ million/ year. The median diagnostic delay decreased from 17 to 4 months. Patients presented most often with symptoms of the ear, nose and throat (ENT) (45%), lung (36%), musculoskeletal system (22%) and kidney (11%). Initial lung involvement, constitutional symptoms, high erythrocyte sedimentation rate (ESR) and high ELK scores [(number of simultaneously involved organ groups (ENT, Lung, Kidney)] were associated with a shorter diagnostic delay. Medical treatment of WG patients remained similar in the 1980s and 1990s. Almost 90% of patients received cyclophosphamide (CYC) and more than 90% glucocorticoid medication at some point during the course of the disease. Eighty-four patients (17%) needed dialysis. Initial renal involvement and elevated serum creatinine values were related to an increased risk of dialysis-dependent kidney disease. In two-thirds of the patients, renal impairment was reversible. Dialysis became chronic (>3 months) in 32 patients (6.5%). Nineteen patients (3.9%) received a kidney transplant. Altogether 203 patients (99 men, 104 women) died before 30 June 2005. WG was the underlying cause of death in 37%. The crude one-year and five-year survival rates were 83.3% and 74.2%, respectively. The standardized mortality ratio was 3.43 (95% CI = 2.98 to 3.94). Older age and elevated creatinine level at diagnosis predicted shorter survival. ENT symptoms at presentation and treatment with CYC were associated with better outcome. There was no additional risk associated with male gender or with either of the decades (1981-1990 and 1991-2000) Conclusions: In 1981-2000, the incidence of WG increased ca. 4.5-fold and diagnostic delay decreased to ca. one-fourth, reflecting increased recognition of the disease and improved diagnostic means. WG patients are at great risk of developing dialysis-dependent renal insufficiency and an increased risk of dying. During the study period the treatment of WG did not change markedly, nor did the prognosis improve.

Synthetic investigations on illudinine: a new synthesis of methyl 8-methoxy-2,2-dimethyl-7-oxo-1,2,3,5,6,7-hexahydro-s-indacene-4-carboxylate

A new strategy for the total synthesis of methyl 8-methoxy-2,2-dimethyl-7-oxo-1,2,3,5,6,7-hexahydro-s-indacene-4-carboxylate 4, a key intermediate in the synthesis of illudalanes, is reported. The key step in this strategy is a new method of preparation of indanones from tetralones. Thus, the furfurylidene derivative of 6-methoxy-3,4-dihydronaphthalen-1-(2H)-one is oxidised to the dicarboxylic acid 9a which is cyclodehydrated to methyl 7-methoxy-1-oxoindan-4-carboxylate 10. Similar reactions on the tetrahydronaphthalenone 25, obtained from 6-methoxy-1,2,3,4-tetrahydronaphthalene-7-carbaldehyde 11 by sequential transformations including a regiospecific benzylic oxidation resulted in the hexahydro-s-indacenone 4, thus completing a formal synthesis of illudinine 1.

The identification of 14 alpha,17 beta-dihydroxyandrost-4-en-3-one monohydrate and 14 alpha,17 beta-dihydroxyandrosta-1,4-dien-3-one monohydrate, metabolites of androstenedione in Mucor piriformis

The microorganism Mucor piriformis transforms androst-4-ene-3,17-dione into a major and several minor metabolites. X-ray crystallographic analysis of two of these metabolites was undertaken to determine unambiguously their composition and chirality. Crystals belong to the orthorhombic space-group P2(1)2(1)2(1), with a = 7.199(4) angstrom and a = 6.023(3) angstrom, b = 11.719(3) angstrom and b = 13.455(4) angstrom, c = 20.409(3) angstrom and c = 20.702(4) angstrom for the two title compounds, respectively. The structures have been refined to final R values of 0.060 and 0.040, respectively.

Nuclear-quadrupole resonance in coordination chemistry- identification of bridiging and therminal chlorines in the mercuric chloride-4-picoline n-oxide complex

The temperature dependence of the chlorine-35 n.q.r. in the mercuric chloride-4-picoline N-oxide complex has been studied from 77 K to room temperature, and the results are used to assign the observed frequencies to terminal and bridging chlorines.