Ethanol catalyzed synthesis of titanocene aryl carboxylate complexes and crystal structure of (η-C5H5)2Ti(2-OH-5-S-O2CC6H3)2

A method for the synthesis of titanocene (IV) aryl carboxylate complexes is presented in this paper. It is based on the fact that alcohol can catalyze the reaction between Cp₂TiCl₂ and aryl carboxylate ligands in the presence of sodium hydroxide (NaOH). The effects of the catalyst on the reaction system were studied and the possible reaction mechanism was proposed. This method was used to prepare a series of titanocene (IV) aryl carboxylate complexes and a macrocyclic titanocene (5,5′-dithiodisalicylato titanocene), whose structure was determined by X-ray diffraction analysis.     

Molecular structure of tetranuclear [{Mo2O(S2CNEt2)(η-O2CCF3)(μ-N-o-tol)2}2(μ-O)(μ-O2CCF3)2] formed upon addition of trifluoroacetic acid to syn-[MoO(μ-N-o-tol)(S2CNEt2)]2

Addition of trifluoroacetic acid to syn-[MoO(μ-N-o-tol)(S₂CNEt₂)]₂ in chloroform affords tetranuclear [{Mo₂O(S₂CNEt₂)(η¹-O₂CCF₃)(μ-N-o-tol)₂}₂(μ-O)(μ-O₂CCF₃)₂] which has been crystallographically characterised. It consists of four molybdenum(V) centres linked via bridging imido, trifluoroacetate and oxo ligands and results from replacement of a dithiocarbamate by two trifluoroacetate ligands.     

Influence of CH3 group of μ-N-C-S ligand on the properties of [Fe2(C4H5N2S)2(NO)4] complex

Bi-nuclear neutral sulfur-nitrosyl iron complex [Fe₂(SR)₂(NO)₄] (I) has been obtained by replacement of thiosulfate ligands in dianion [Fe₂(S₂O₃)₂(NO)₄]²⁻ by 1-methyl-imidazole-2-yl. From X-ray analysis data, the complex has centrosymmetrical dimeric structure, with the iron atoms being linked via μ-N-C-S bridge. From Mossbauer spectroscopy, isomeric shift δ_Fe is 0.180(1) mm/s and quadrupole splitting ΔE_Q is 0.928(2) mm/s at T = 290 K. By comparative studying the mass-spectra in the gaseous phase of solid samples decomposition and kinetics of NO release in 1% aqueous solutions of dimethylsulfoxide, using of the ligand with CH₃ substituent in position 1 of imidazole-2-thiol was shown to yield a more stable donor of nitrogen monoxide than earlier obtained analog with imidazole-2-thiol, [Fe₂(C₃H₃N₂S)₂(NO)₄].     

Synthesis of 11β-3H-prostaglandin E2

11β-³H-Prostaglandin E₂ was synthesized by the stereoselective reduction of the PGD₂ derivative $\text{2}$ using sodium borotritide.     

Omega chain methylated analogs of PGF2α and PGE2

Our previously published prostaglandin (PG) synthesis route, in which the ω-chain is added in the penultimate step, provides facile access to a wide variety of ω-chain variant PG analogs. Each series requires only the synthesis of the appropriate methylated acylphosphonate for the Emmons' condensation. The syntheses of analogs bearing the following methylation pattern are detailed: 15-Me; 17, 17-(Me)₂; 17, 17, 20-(Me)₃; 18, 18, 20-(Me)₃; 15, 18, 18, 20-(Me)₄; and 15-Ome-18, 18, 20-(Me)₃. The well-known 16, 16-dimethyl prostaglandins have also been prepared by this sequence. The synthesis of 16, 16-tetramethylene-PG analogs is also described.     

The reactions of 2-hydroxypyridine ligands with Re2Cl4(μ-dppm)2 (dppm=Ph2PCH2PPh2) that lead to 2-pyridonate complexes

2-Hydroxypyridine (Hhp), 2-hydroxynicotinic acid (HnicOH) and 6-hydroxypicolinic acid (HpicOH) react with Re₂Cl₄(μ-dppm)₂ (dppm=Ph₂PCH₂PPh₂) to afford the complexes Re₂(η²-hp)Cl₃(μ-dppm)₂ (1), Re₂(η²-HnicO)Cl₃(μ-dppm)₂ (2) and Re₂(μ-picO)₂(μ-dppm)₂ (3). The identities of 1 and 2 have been established by single-crystal X-ray structure determinations (Re-Re distances of 2.2602(3) and 2.2539(3) Å, respectively) and they are shown to have unsymmetrical structures with staggered rotational geometries and trans, cis coordination of the pair of μ-dppm ligands. The crystal of 2 that was used in the structure determination was found to be of composition 2Re₂(η²-HnicO)Cl₃(μ-dppm)₂ · Re₂Cl₆(μ-dppm)₂ · 2.906CH₂Cl₂. The structure of Re₂Cl₆(μ-dppm)₂ in this crystal is compared with structures reported in the literature for other crystals that contain this edge-sharing bioctahedral dirhenium(III) complex.     

Comparison of the effects of prostaglandins D2, F2α and E1 on spontaneous contractions of rabbit oviduct

The effects of PGD₂, PGF_2α and PGE₁ were studied on the circular muscle of post-ovulatory rabbit oviducts $\text{in vitro}$. PGE₁ inhibited spontaneous contractile activity. Lower concentrations of PGD₂ and PGF_2α were stimulatory and higher concentrations were inhibitory. Since PGD₂ may be produced in the oviduct, any hypothesis concerning the role of prostaglandins in the control of oviductal motility and ovum transport should include PGD₂ as well as PGFs and PGEs.     

The synthesis of Δ2-prostaglandins

The effect of prostaglandin F_2α on ovulation and fertilization was studied in rabbits. The number of ovulation was not affected by subcutaneous injection of PGF_2α but the recovery of ova was significantly decreased when PGF_2α was given either at 12 or 16 h after HCG injection and autopsied 24 h latter. The results suggest that exogenous PGF_2α accelerates ovum transport and expels the eggs prematurely from the female tract and does not impair ovulation or the fertilization processes when given to rabbit at 1 mg/kg B.W.     

Voltammetry of half-sandwich manganese group complexes of η-PhC3B7H9 and η-C60Bn2PhH2, two ligands that are cyclopentadienyl mimicks

The potentials of a series of one-electron oxidation and reduction reactions have been determined for manganese group half-sandwich complexes of the tricarbadecaboranyl ligand PhC₃B₇H₉ and the penta-organo fullerene ligand C₆₀Bn₂PhH₂ (Bn = benzyl). The anodic processes were studied in CH₂Cl₂ and the cathodic processes were studied in both CH₂Cl₂ and THF, the supporting electrolyte being [NBu₄][B(C₆F₅)₄]. The manganese complex Mn(CO)₂(PMe₃)(PhC₃B₇H₉) (1) is a member of a three-electron transfer series which includes oxidation to 1⁺ (0.51 V versus ferrocene) and successive reductions to 1⁻ (−1.66 V) and 1²⁻ (−1.77 V). Both the oxidation and reduction of the closely-related complex Mn(CO)₂(PPh₃)(PhC₃B₇H₉) (2) are chemically irreversible under slow-scan cyclic voltammetry conditions. The rhenium complex Re(CO)₂(PPh₃)(PhC₃B₇H₉) (3) oxidizes (E_1/2 = 0.82 V versus ferrocene) to a radical cation which, unlike its cyclopentadienyl analogue, shows no evidence of dimerization. Oxidation of the fullerene-based complex Re(CO)₃(C₆₀Bn₂PhH₂) is more facile than that of its cyclopentadienyl analogue, in contrast to previous findings in this class of metal-fullerene derivatives. An electrochemical ligand factor, E_L, of 0.63 is calculated for the PhC₃B₇H₉ ligand in manganese group half-sandwich complexes.     

The effects of prostaglandins E2 and F2α on synaptosomal accumulation and release of 3H-norepinephrine

Prostaglandins (PG) of both the E and F series may serve as modulators of norepinephrine (NE) release from peripheral sympathetic neurons. We have studied the effects of PGE₂ and PGF_2α on the accumulation and release of ³H-NE in the CNS using synaptosomes isolated from rat hypothalami.The release of ³H-NE from synaptosomes superfused with Krebs-Ringer bicarbonate buffer was multiphasic with an initial fast release phase followed by a slower release. Raising KC1 concentration of the superfusion medium to 56mM during the slow release phase is known to stimulate ³H-NE release. PGE₂ (1 × 10^?6M) attenuated ³H-NE release during the fast phase and reduced the amount of ³H-NE released due to KC1 stimulation. At lower concentrations of PGE₂ there was no change in the release profile. PGF_2α was without effect on ³H-NE release at all concentrations tested.The accumulation of ³H-NE was significantly diminished by PGE₂ at a concentration of 1 × 10^?6M, while a lower concentration (1 × 10^?7M) was ineffective. PGF_2α had no effect on ³H-NE accumulation at all concentrations investigated.     

H2O2− and alkyl hydroperoxide-supported para hydroxylation of aniline by alkaline hematin

Under alkaline conditions and in the presence of reductant, NADH or NADPH, and molecular oxygen, hemin catalyzes the regiospecific para-hydroxylation of aniline to form p-aminophenol [P.A. Adams, D.A. Baldwin, and M.C. Berman, J. Chem. Soc. (Lond) Chem. Commun. 856 (1979); P.A. Adams and M.C. Berman, J. Inorg. Biochem.17, 1 (1982)]. The reaction has now been studied in the presence of H₂O₂ and alkyl hydroperoxides and in the absence of oxygen and reductant. Results indicate that the H₂O₂^? and alkyl hydroperoxide-supported processes proceed via different mechanisms involving, on the one hand, the hydroperoxide anion (HO₂^?) and on the other, the undissociated alkyl hydroperoxide molecule (ROOH). The addition of superoxide dismutase to the reaction had no effect, unlike the NADH/O₂ supported reaction where the enzyme completely inhibits reaction. Similarities between the hemin-mediated peroxide-supported reactions reported here, and the cytochrome P-450-mediated peroxide-supported reactions reinforce our earlier contentions that the alkaline hemin system appears to be a good model for the in vivo activation of oxygen by hemoproteins.     

A simple method for preparation of valency hybrid hemoglobins, (α3+β2+)2 and (α2+β3+)2

The improved methods for the preparation of valency hybrid hemoglobins, (α³⁺β²⁺)₂ and (α²⁺β³⁺)₂ were presented. The (α³⁺β²⁺)₂ valency hybrid was separated from the solutions of partially reduced methemoglobin with ascorbic acid, by using CM 32 column chromatography. The (α²⁺β³⁺)₂ valency hybrid was also isolated from hemoglobin solutions, which were partially oxidized with ferricyanide, by chromatography on CM 32 column. These valency hybrid hemoglobins were found to be single on isoelectric focusing electrophoresis. Present procedures are very simple and are suitable for the bulk preparation of (α³⁺β²⁺)₂ and (α²⁺β³⁺)₂ valency hybrids.     

Synthesis and structural characterization of the molecular loop [cis-Mo2(N,N-di-p-anisylformamidinate)2]2(O2C-CHCCH-CO2)2

A new molecular loop composed of two quadruply bonded Mo₂(DAniF)₂ units (DAniF=N,N^′-di-p-anisylformamidinate) linked by two chiral allene-1,3-dicarboxylate anions has been prepared from the reaction of [cis-Mo₂(DAniF)₂(MeCN)₄](BF₄)₂ with the bis(tetraethylammonium) salt of allene-1,3-dicarboxylic acid. This compound, [cis-Mo₂(DAniF)₂]₂(O₂C-CHCCH-CO₂)₂ (1), has been characterized by X-ray crystallography and by ¹H NMR and UV-Vis spectroscopy. The molecule possesses a center of inversion and hence is meso. There is only weak electronic coupling between the two Mo₂ ⁴⁺ units as revealed by electrochemical measurements.     

Characterization of the lys2 gene of Penicillium chrysogenum encoding α -aminoadipic acid reductase

A DNA fragment containing a gene homologous to LYS2 gene of Saccharomyces cerevisiae was cloned from a genomic DNA library of Penicillium chrysogenum AS-P-78. It encodes a protein of 1409 amino acids (Mr^ 154 859) with strong similarity to the S. cerevisiae (49.9% identity) Schizosaccharomycespombe (51.3% identity) and Candida albicans (48.12% identity) α-aminoadipate reductases and a lesser degree of identity to the amino acid-activating domains of the non-ribosomal peptide synthetases, including the α-aminoadipate-activating domain of the α-aminoadipyl-cysteinyl-valine synthetase of P. chrysogenum (12.4% identical amino acids). The lys2 gene contained one intron in the 5′-region and other in the 3′-region, as shown by comparing the nucleotide sequences of the cDNA and genomic DNA, and was transcribed as a 4.7-kb monocistronic mRNA. The lys2 gene was localized on chromosome III (7.5 Mb) in P. chrysogenum AS-P-78 and on chromosome IV (5.6 Mb) in strain P2, whereas the penicillin gene cluster is known to be located in chromosome I in both strains. The lys2-encoded protein is a member of the aminoacyladenylate-forming enzyme family with a reductase domain in its C-terminal region. Received: 26 January 1998 / Accepted: 4 May 1998     

Ligand induced PH bond formation and a comparison of the reactivity of two isomers of the carbonyl hydride [Pt2(μ-PBu2)2(H)(CO)(PBu2H)]CF3SO3

The Pt₂ ^(II) isomeric terminal hydrides [(CO)(H)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)]CF₃SO₃ (1a), and [(CO)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)(H)]CF₃SO₃ (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the Pt₂ ^(I) dicarbonyl [Pt₂(μ-PBu^t ₂)(CO)₂(PBu^t ₂H)₂]CF₃SO₃ (3-Pt); the solid state structure of the isomer bearing the carbonyl ligands pseudo-trans to the bridging phosphide was solved by X-ray diffraction. A remarkable difference was instead found between the reactivity of 1a and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt₂(μ-PBu^t ₂)(μ,η²,η²-CS₂)(PBu^t ₂H)₂]CF₃SO₃ (4-Pt), and [Pt₂(μ-PBu^t ₂)(μ,η²,η²-isoprene) (PBu^t ₂H)₂]CF₃SO₃ (6-Pt), respectively. In the same experimental conditions, 1a is totally inert. A common mechanism, proceeding through the preassociation of the incoming ligand followed by the PH bond formation between one of the bridging P atoms and the hydride ligand, has been suggested for these reactions.     

Preparation of cobalt sandwich diphosphine ligand [(η-C5H4Pr)Co(η-C4(PPh2)2Ph2)] and its chelated palladium complex: Application of diphosphine ligand in the preparation of mono-substituted ferrocenylarenes

The reaction of (η⁵-C₅H₄ⁱPr)Co(PPh₃)₂ with PhCCPPh₂ furnished two isomeric cyclobutadiene-substituted Cp′CoCb diphosphines, [(η⁵-C₅H₄ⁱPr)Co(η⁴-1,2-(PPh₂)₂C₄Ph₂)] (5-cis) and [(η⁵-C₅H₄ⁱPr)Co(η⁴-1,3-(PPh₂)₂C₄Ph₂)] (5-trans). Further reaction of 5-cis with one molar equivalent of Pd(COD)Cl₂ gave palladium complex [(η⁵-C₅H₄ⁱPr)Co(η⁴-1,2-(PPh₂)₂C₄Ph₂)-PdCl₂] (6) in good yield. Both of the molecular structures of 5-cis and 6 were determined by single-crystal X-ray diffraction methods. Unexpectedly, the palladium complex 6 was found to be more efficient than the combination of the commonly used Buchwald’s ligand, biphenyl-2-yl-di-tert-butyl-phosphane, with Pd(OAc)₂ as the catalytic precursor in the Suzuki-Miyaura reaction between ferroceneboronic acid and 4-bromoaldehyde. The X-ray structural analysis and DFT study of several palladium complexes containing sandwich-type diphosphine chelating ligands revealed that the variations in bite angles are much larger than those in bite distances. The more energetically favorable conformation in the Pd(II) complexes is the one with bite angle close to 90°.     

The effect of prostaglandins A2,E1,E2,15 methyl E2, 16, 16 dimethyl E2 and F2α on erythropoiesis

Prostaglandins A₂, E₁, E₂, methylated E₂s and F₂α affected erythropoiesis and/or erythropoietin (Ep) production. This action is indicated in the exhypoxic, polycythemic mouse where radioiron incorporations into RBC increased after administration of these compounds. The kidney and liver have been indicated through previous studies, to actively participate in Ep production. By the removal of one of these active sites in a murine system treated with prostaglandins it is shown that a response is reflected in Ep levels. Interference of the action of prostaglandins (PG) is altered by the removal of one of these target sites of Ep production. The erythropoietic responses elicited by PGA₂, E₁, and perhaps the methylated PGE₂s act through the liver whereas PGE₂ may operate through a renal pathway for its response. PGF_2α reveals no effect on erythropoietic activity and is no different than that observed for vehicle-treated controls. The prostaglandins tested appear to act primarily through the kidney or liver but the possibility exists that some yet undetermined organ site may also be involved.     

Control of the modularity of {Mo2O2S2}-containing polyoxometalates. Synthesis, structure and characterization of tri- and tetra-modular assemblies based on the [β-B-AsW9O33] anion

Reaction at pH = 2.3 of the [Mo₂O₂S₂(OH₂)₆]²⁺ aqua cation with the tetravacant ion [β-B-HAs₂W₈O₃₁]⁷⁻ leads to the formation of a red solid from which three mixed salts have been obtained as single crystals and characterized by X-ray diffraction analysis. Three mixed salts K-5a, RbNa-5b, DMACs-5c exhibit a similar molecular arrangement consisting in three {β-HAs₂W₉O₃₄} subunits mutually linked by three {Mo₂O₂S₂} groups. The triangular arrangement delimits a large open-cavity, lined on the periphery by three outer {As-OH} groups and closed at the bottom by a small hexagonal pocket formed by six terminal oxygen atoms. The central hexagonal cavity is filled either by a potassium, a rubidium or a cesium cation. The outer {As-OH} groups are pointed towards two directions labelled up and down, respectively. In K-6a the three {As-OH} bonds are in up configuration leading to the {up, up, up} isomer. The structure of RbNa-5b is rather consistent with the superposition of the two {up, up, up} and {down, up, up} isomers disordered over the same crystallographic site, while only the {down, up, up} isomer is present in DMACs-5c. In solution, ¹⁸³W NMR characterization of 6a as sodium salt results in a complicated spectrum consistent with the simultaneous presence of the four isomers, {up, up, up}, {down, up, up}, {down, down, up} and {down, down, down}, respectively. 5a reacts with three equivalents of iodine to give CsNa-6 isolated as single crystals. In 6, four β-{AsW₉O₃₃} moieties are located at the corner of a super tetrahedron and are mutually connected by six {Mo₂O₂S₂} linkers. The three outer {As-OH} groups can be selectively removed by iodine, this oxidation reaction consisting in fact in a deprotecting process permitting the extension of the arrangement from triangular to tetrahedral.     

On the solvatochromic properties of the oxalate-bridged complexes [(BuCO2)3M2]2(μ-O2C2O2) where M = Mo or W

The room temperature electronic absorption spectra of the oxalate bridged MM quadruply bonded complexes [(^tBuCO₂)₃M₂]₂(μ-O₂C₂O₂), where M = Mo or W have been recorded in H₂O, THF:H₂O mixtures, THF, CH₂Cl₂, toluene, DMSO, aniline, toluene saturated with N,N-dimethylaniline and ethanol. The strong absorptions in the visible region of the electronic absorption spectra assignable to the metal-to-ligand (bridge) charge transfer are shown to be highly solvent dependent. Those samples prepared in H₂O, CH₂Cl₂ and toluene are shown to comprise of a suspension of microcrystalline particles ranging in size from 100 nm to 5 μm. Individual particles were found by scanning electron microscopy to have an aspect ratio of ∼10:1, all being needle shaped. The spectra in THF, EtOH, aniline, DMSO and toluene-N,N-dimethylaniline all show similar vibronic progressions and are attributed to discrete solvated molecular species. The spectra recorded in aniline are notably red-shifted which is proposed to arise from a combination of hydrogen bonding and Lewis base stabilization of the photoexcited state.