Syntheses of Bile Pigments. Part 16. Synthesis of a vinyl-substituted 2,3-Dihydrobilinedione: Possible role of this new class of bile pigments in phycobilin biosynthesis

The total synthesis of racemic cis-2,3,18¹, 18², -tetrahydroprotobiliverdin IXα dimethyl ester ( 19b ), which is identical with the dimethyl ester of rac- 4 , is described (Scheme 2). Under virtually neutral conditions, in solution, this bile pigment isomerized within a few min to racemic Z-phycocyanobilin dimethyl ester (rac- 5b ). Likewise, acid-catalyzed allyl rearrangement of 3-vinyl-substituted cis- and trans-2,3-dihydrodipyrrin-1(10H)-ones 11c and 13c , respectively, yielded the corresponding ethylidene derivatives. In this case, however, the E-isomer was formed stereo selectively from both substrates. The above results prove that, if protobiliverdin IXα ( 2 ) is transformed enzymatically to its 2,3,18¹, 18²-tetrahydro derivative, the latter would isomerize spontaneously to phycocyanobi-lin. The biosynthesis of bacteriochlorophyll a and b from a common precursor bearing a vinyl group at C(8)may be straightforwardly explained in the same way.     

Singlet molecular oxygen quantum yield measurements of some porphyrins and metalloporphyrins

Hematoporphyrin IX dimethyl ester (HPDME), tetraphenylporphyrin (TPP), tetra(4-methoxyphenyl)porphyrin (TMPP), tetra(3,4-dimethoxyphenyl)porphyrin (TDMPP), tetra(3,4,5-trimethoxyphenyl)porphyrin (TTMPP), tetraanthrylporphyrin (TAP) and tetraacridylporphyrin (TACP), and their Zn²⁺, SnX ₂ ²⁺ , Pd²⁺ and Pt²⁺ complexes have been prepared and characterized. The singlet molecular oxygen quantum yield (ϕ_Δ) values of the above porphyrins and their metal derivatives in N,N-dimethyl formamide (DMF) have been measured in the presence of 1,3-diphenylisobenzofuran (DPBF) as¹O₂ acceptor using steady state technique after correcting for the intensity of light absorbed by the photosensitizers. The ϕ_Δ values for the free base porphyrins are usually around 0.60. Hematoporphyrin IX dimethyl ester and its metal derivatives follow the order: HPDME (ϕ_Δ = 0.60) > Zn HPDME (0.40) > PdHPDME (0.34) > Sn(OH)₂ HPDME (0.28) > PtHPDME (0.24). Zinc(II) complexes of tetraarylporphyrins show about 65% efficiency in ϕ_Δ values are compared to the ϕ_Δ values of their corresponding free base porphyrins. These results can be explained on the basis of catalyzed intersystem crossing to the ground state. The ϕ_λ values of the above free base porphyrins and their metal complexes in DMF in presence of DPBF using single-pulsed laser excitation technique follow similar trends.     

Synthesis of Novel Dibenzo‐18‐crown‐6‐ ether‐Functionalized Benzimidazoles and its Applications in Colorimetric Recognition to Hg2+ and as Antifungal Agents

New crown ether‐functionalized benzimidazoles was designed and synthesized via formylation of dibenzo‐18‐crown‐6 followed by condensation with different o‐phenylene diamines. The complexation properties of crown ether‐functionalized benzimidazoles with various metals (K⁺, Ca²⁺, Ba²⁺, Co²⁺, Hg²⁺) were examined using UV–vis spectroscopy. Hg²⁺ showed a well‐defined peculiar absorption maximum at 366 nm exclusively. All these newly synthesized compounds were screened for antifungal activity against Aspergillus niger and Aspergillus oryzae, respectively.     

A Spectropotentiometric Study of Association Equilibria of Cationic Acids of Mesoporphyrin IX Dimethyl Ester with Iodide Ions in Acetonitrile

The association equilibrium of porphyrinium ions of mesoporphyrin IX dimethyl ester (H₂MP) with iodide ions in acetonitrile was studied by spectropotentiometric titration. Two associates were revealed: (H₄MP^{2 +})(I^-) and (H₄MP^{2 +})(I^-)₂; the electronic absorption spectra of these species were measured, and their formation constants were determined.     

Photocatalytic degradation of dimethyl phthalate ester using novel hydrophobic TiO2 pillared montmorillonite photocatalyst

TiO₂ pillared montmorillonites were prepared by introducing Ti⁴⁺ into a layer of montmorillonite modified with or without cetyltrimethylammonium bromide. The components and texture of the prepared composites were characterized by thermogravimetric analysis, X-ray powder diffraction and scanning electron misroscopy. The adsorption and photocatalytic degradation performance of a model environmental endocrine disruptor, dimethyl phthalate ester, were investigated using this newly prepared hydrophobic TiO₂ pillared montmorillonite photocatalyst. The adsorption of dimethyl phthalate ester from water varied from 9% to 28% on the prepared hydrophobic photocatalyst. Although the experimental results showed that the photocatalytic activity of the hydrophobic photocatalyst was slightly lower than that of hydrophilic one, electron spin resonance verified that hydroxyl radicals were also generated in hydrophobic TiO₂ pillared montmorillonite photocatalyst under UV irradiation. To elucidate the decomposition mechanism of dimethyl phthalate ester, 12 main photocatalytic intermediates were identified during the photocatalytic degradation process, and a plausible degradation mechanism was also proposed.     

Activation of nitrite ion by biomimetic iron(III) complexes

The rate of reaction of NO ₂ ⁻ ion with various Fe^III porphyrins in the presence of PPh₃ is shown to depend on the redox potential of the Fe^III center. There is a linear relationship between the ease of reduction of the Fe^III to Fe^II and the kinetics for the formation of the Fe^II porphyrin nitrosyl adduct, with concomitant oxidation of PPh₃ to PPh₃O. Cyclic voltammograms show reversible one-electron reductions that can be ascribed to the Fe^III/Fe^II couple ranging from E_1/2 = −343 to −145 mV (versus Ag/AgCl). The order of increasing half-wave reduction potentials for the Fe^III/Fe^II porphyrin redox centers studied is octaethylporphyrin > etioporphyrin I > deuteroporphyrin IX dimethyl ester > protoporphyrin IX dimethyl ester > α,β,γ,δ-tetraphenylporphyrin. This sequence of redox potentials complements the pseudo first-order kinetics ( to m s ⁻¹) for the oxidation of PPh₃ and subsequent Fe^II porphyrin nitrosyl adduct formation. The rates of reaction of biomimetic Fe^III porphyrins with NO ₂ ⁻ ion demonstrate how metal center redox properties are influenced by the surrounding ligand. In this paper we have elucidated a possible mechanistic control for the rate of this reaction.     

Synthesis of Novel 4‐((Substituted bis‐indolyl)methyl)‐benzo‐15‐crown‐5 for the Colorimetric Detection of Hg2+ Ions in an Aqueous Medium

A practical, two‐step synthesis of novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 has been reported. The strategy employed for the synthesis of the desired molecules involved Duff formylation of benzo‐15‐crown‐5 to get 4‐formyl benzo‐15‐crown‐5 followed by subsequent reactions with substituted indoles in trifluoroacetic acid to yield novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 in moderate to good yield. One of the reported novel molecule tested for the complexation behavior with various metal cations, such as Li⁺, Na⁺, K⁺, Mg²⁺ Ca²⁺, Al³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn²⁺, Ba²⁺, Hg²⁺, and Pb²⁺, showed a visual colorimetric probe for the detection of mercury cations (Hg²⁺) in an aqueous medium.     

On the Novel Free Porphyrins Corallistin B,C, D,and E: Isolation from the demosponge Corallistes sp. of the Coral Sea and Reactivity of Their Nickel 55 (II) Complexes toward Formylating Reagents

Reported here are the novel free porphyrins corallistin B, C, D, and E, isolated as methyl esters 2a , 3a , 4a , and 5a , respectively, from the sponge Corallistes sp. (Lithistida) collected at the basis of the south New Caledonian coral reef. A protocol is also established for formylation of their Ni^II complexes, which show a different reactivity pattern toward DMF/POCl3 from metal complexes of deuteroporphyrins. Together with corallistin A, Previously isolated as the methyl ester 1a , and the known deuteroporphyrin IX (isolated as 6a ) also present in the sponge, the new corallistins, which may be thought to derive from protoporphyrin via heme, account for an amazing 60% of the EtOh extract from the sponge.     

A simple, catalytic H2-hydrogenation method for the synthesis of fine chemicals; hydrogenation of protoporphyrin IX dimethyl ester

A conceptually simple H₂-hydrogenation protocol is introduced for the high-yield preparation of a natural product derivative. Protoporphyrin IX dimethyl ester is hydrogenated to the mesoporphyrin analogue in N,N-dimethylacetamide under H₂ (1 atm) at 80 °C within 30 min. The reaction is catalyzed by commercial RuCl₃, without the need for the use of phosphine- and/or carbene-based ligands.     

Synthesis of novel lactam ionophores containing crown ether moieties and investigation of their extraction abilities towards heavy metal cations

The article describes the syntheses and extraction properties of new lactam ionophores. These lactam derivatives were easily synthesized via aminolysis of dimethyl 2,2′-(6,6′-methylenebis(2-tert-butyl-4-methyl-6,1-phenylene)bis(oxy))diacetate or dimethyl 2,2′-(2,2′-methylenebis(4-chloro-2,1-phenylene))bis(oxy)diacetate with corresponding diamine compounds at one step. The extraction studies of lactam ionophores were performed toward dichromate anion and alkaline and transition metals such as Li⁺, Na⁺, K⁺, Co²⁺, Hg²⁺ and Pb²⁺. All the structures of the ionophores were confirmed by spectroscopic techniques and elemental analysis.     

Pyrrole studies—XXIV: The reactions of 1-methyl-2-vinylpyrrole and 1-phenyl-2-vinylpyrrole with dimethyl acetylenedicarboxylate

The reaction of dimethyl acetylenedicarboxylate with 1-methyl-2-vinylpyrrole is temperature dependent. At 80° the predominant reaction is the [4π + 2π] cycloaddition to give dimethyl 1-methyl-6,7-dihydroindole-4, 5-dicarboxylate, whereas at room temperature Michael addition of the acetylenic ester at the 5-position of the pyrrole ring to give fumaric and maleic ester derivatives also occurs. Unequivocal assignment of the configurations of the Michael adducts have been made on the basis of their ³J_CO,h coupling constants. 1-Phenyl-2-vinylpyrrole reacts with dimethyl acetylenedicarboxylate to give only the [4π + 2π] cycloadduct at room temperature and at elevated temperatures.     

Photophysical Properties of Sol–gel derived Luminescent Silicone Hybrids Synthesized via Facile Amino‐Ene Reaction

Novel luminescent silicone hybrids (LSHs) containing lanthanide ions were prepared via different sol–gel processes. The precursor, dimethyl ester‐functionalized silane, was synthesized via a facile amino‐ene reaction. The coordinated assembly of the ester ligands and lanthanide ions (Eu³⁺, Tb³⁺ and Dy³⁺) occurred. The ester ligands were immobilized onto the Si‐O network backbone during the preparation of the silicone hybrid materials. The particle size can be controlled to ca 50 nm by adjusting the solvent ratio. The obtained materials were characterized by Fourier transform infrared, ¹H nuclear magnetic resonance spectroscopy (NMR), ¹³C NMR, ²⁸Si NMR, X‐ray diffraction, X‐ray photoelectron spectroscopy, thermogravimetric analysis, high‐resolution scanning electronic microscopy and luminescent (excitation and emission) spectroscopy. The coordination state and photophysical performance of the compounds were studied in detail. The terbium‐ and europium‐containing materials show sharp green and red emissions, respectively, which indicate that efficient intramolecular energy transfer took place in these LSHs.     

Calix[4]arenes with carboxamide and sulfonamide groups and their complexation with transition metal salts

Calix[4]arene derivatives functionalized by ester and carboxamide groups on the lower rim and sulfonamide groups on the upper rim were synthesized, and their complexing properties toward transition metal salts (Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺) were studied by extraction in chloroform-water system. The presence of carboxamide and sulfonamide fragments in the ligand was shown to considerably enhance binding of transition metal cations.     

Spectroscopic studies of novel porphyrin-copper(II) and zinc(II) complexes that share the pinch-porphyrin family structure of iron(III) complex models of peroxidases

Six novel pinch-porphyrin complexes [(picdien)(protoporphyrinate dimethyl ester)]copper(II) (7), [(picdien)(mesoporphyrinate dimethyl ester)]copper(II) (8) and [(picdien)(deuteroporphyrinate dimethyl ester)]copper(II) (9), [(picdien)(protoporphyrinate dimethyl ester)]zinc(II) (13), [(picdien)(mesoporphyrinate dimethyl ester)]zinc(II) (14) and [(picdien)(deuteroporphyrinate dimethyl ester)]zinc(II) (15), were prepared from the corresponding free copper(II)-porphyrins (4–6), and zinc(II)-porphyrins (10–12) and picdien (N-(3H-imidazol-4-ylmethyl)-N-{2-[(3H-imidazol-4-ylmethyl)-amino]-ethyl}-ethane-2,3-diamine). Spectroscopic studies show that complexes (7–9) and (13–15) have the pinch-porphyrin type structure previously found in iron(III) complex models of peroxidases. Complexes (7–9), were characterized by u.v.–vis., m.c.d., and e.s.r. spectroscopy. E.s.r. spectra of the copper parent compounds (4–6) at ca. 10^–2–10^–4 M concentrations were typical of copper(II)-dimers. The addition of the picdien ligand broke up the dimers as detected by e.s.r. Compounds (7–9) are predominantly monomeric at ca. 10^–3 M concentration. The presence of picdien in (7–9) distorts the porphyrin internal portion of the plane so as to make these four internal nitrogen atoms, coordinated to copper(II), e.s.r.-distinguishable. MO and ligand field theories were used to characterize and to evaluate the directional covalence parameters of compounds (7–9). A non-fully axial, out-of-the-porphyrin-plane bonding was found for (7–9), similar to the bonding of the pinch-porphyrins-iron(III). However the in-plane distortion produced by the presence of the picdien ligand on copper(II) is significantly larger than in pinch-porphyrin-iron(III). The n.m.r. data show that the porphyrin-zinc(II) is the less strained and has the weakest bonded structure. The coordination number of the pinch-porphyrin with iron(III), copper(II) and zinc(II), is in all cases six.     

OXIDATIVE DEGRADATION OF BILIVERDIN AND BILIRUBIN ESTERS IN PRESENCE OF SILVER NITRATE

Treatment of biliverdin IXα dimethyl ester(2)with silver nitratein alkaline solution gave two violin-like tripyrrione carbaldehydes, one de-graded at C15-C16, other at C4-C5.Biliverdin IXα(1), bilirubin IXα(3)and its dimethyl ester(4)gave the same results.     

Sensitized photo-redox reaction: VII. The Synthesis,FAB mass spectrum,stationary absorption,emission, transient absorption spectra,redox potential of dihydroxy-tin (IV)-mesoporphyrin dimethyl ester and its sensitized photo-reduction of methyl viologen

In DMSO/water (4:1), photolysis of the dihydroxy-Sn (IV)-mesoporphyrin dimethyl ester (SnP)/methyl viologen (MV²⁺)/ethylene diamine tetraacetic acid (EDTA) ternary system produces methyl viologen cation radical with a quantum yield of 0.67, much higher than that of systems with other metal complexes of mesoporphyrin dimethyl ester. Neither EDTA nor MV²⁺ quenches the stationary fluorescence of SnP, implying that the reaction does not take place at the singlet state. With flash photolysis we obtain the T-T absorption spectrum of SnP (λ_max 440 nm). By following the decay of this absorption, the triplet life time of SnP is estimated to be 41 μs. The life time is related to the concentration of either MV²⁺ or EDTA. Good linear relationships are obtained by plotting τ₀τ vs. the concentration of MV²⁺ or EDTA (Stern-Volmer plot), from which we determine the quenching constants: _kq(MV²⁺) =5.5 × 10⁷ mol^?1, s^?1; k_q (EDTA) =2.7 × 10⁷ mol^?1, s^?1. The data suggests that upon photolysis of the above ternary system, both oxidative quenching and reductive quenching of the triplet state of the sensitizer are occurring. From the measured phosphorescence spectrum (λ_max 704 nm) and the ground state redox, potentials (E^red_1/2?-0.84V, E^ox_1/2?+1.43 V, vs. Ag/AgCl, KCl (sat.)), we obtain the redox potential of triplet SnP to be E(P⁺/P*_T)?-0.33 V, E(P*_T+/P^?)?+0.92 V. Matching this data with the redox potential of MV²⁺ and EDTA, we establish the fact that during the photolysis of the SnP/MV²⁺/EDTA ternary system, both oxidative and reductive quenching are thermodynamically favorable processes. This is also the reason why the SnP sensitized reaction is much more efficient relative to other mesoporphyrin derivatives.     

2‐Chloro‐3‐(dimethylamino)prop‐2‐enoyl Fluoride,a Stable Acyl Fluoride

The title compound is formed as a side‐product in the reaction of CF₃CCl₃ with Zn/DMF and dimethyl(thexyl)silyl chloride (=dimethyl(1,1,2‐trimethylpropyl)silyl chloride). The structure and the double‐bond configuration are deduced from its ¹³C‐NMR data. Its formation is discussed in terms of a Vilsmeier‐type formylation and a reductive elimination.     

The reaction of metalloporphyrins with nitrogen dioxide

The octaethylporphyrin(OEP) complexes of iron(III) chloride, iron(III) acetate, thallium(III) hydroxide, zinc(II), and cobalt(II) and the mesoporphyrin IX dimethyl ester (MPDME) complexes of zinc(II) and iron(III) chloride were reacted with a 20:1 ratio of NO₂ to metalloporphyrin in CH₂Cl₂. The +3 metalloporphyrins gave products which had a nitromethyl group in each of the four meso positions of the porphyrin ring and a chloride ion bound to the metal atom. The products of +2 metalloporphyrin reaction had a nitro group bound in each of the meso positions. The spectral and electrochemical properties of some of the products were measured. ³⁶Cl labelled OEPFeCl was reacted with NO₂ in CH₂Cl₂. The product, meso-tetranitromethyl OEPFeCl, had 17% of the original activity which indicates that the chloride ion bound to the iron is exchanged with chloride ions formed in the reaction. The nitromethylation reaction appears to involve initially the displacement of chloride from iron(III) by NO₂ and solvent attack on the bound NO₂. The meso-nitration of the +2 metalloporphyrin by NO₂ has been proposed to proceed by a π-cation radical mechanism (E.C. Johnson and D. Dolphin, TetrahedronLetters 2197 (1976).     

Antioxidative effect of several porphyrins on lipid peroxidation in rat liver homogenates

The effect of several porphyrins on Fe2(+)-ascorbic acid-stimulated lipid peroxidation was examined in rat liver homogenates. Not only protoporphyrin IX (PP) but also mesoporphyrin IX and hematoporphyrin inhibited the lipid peroxidation. Some porphyrins, in which 6- and 7-carboxyethyl groups were esterified with a methyl group, such as protoporphyrin IX dimethyl ester and mesoporphyrin IX dimethyl ester, had no antioxidative effect. Hemin and zinc protoporphyrin IX, which are metal-chelated porphyrins, inhibited the lipid peroxidation while cobalt protoporphyrin IX and tin protoporphyrin IX showed no antioxidative effect. Thus, some of the porphyrins used in the present study showed an antioxidative effect as did PP, but the others did not show such an effect.     

Spectrophotometric determination of ruthenium

Zusammenfassung Es wurde festgestellt, daß die Mehrzahl der Amidoxime mit folgenden Ionen reagiert: Hg²⁺, Cu²⁺, Fe³⁺, Co²⁺, UO₂ ²⁺, Cd²⁺, Ag^+;, Pb²⁺, Pd²⁺, Ni²⁺. Von den Malonsäure-bis-amidoximen wurden hergestellt die Silber-, Blei-, Cadmium-, Kupfer- und zwei Quecksilbersalze, von den Amidoximen der Nicotin- und Isonicotinsäure Palladium-, Kupfer-, Cadmium- und Bleisalze. Die Salzbildungsfähigkeit der Amidoximgruppe ist vom Radikal, von den Substituenten an der Amidgruppe und vom Reagens-medium abhängig. Die braunrote Färbung mit Fe³⁺-Ionen ist für alle Amidoxime typisch, diese Reaktion kann zum Nachweis der am Amidstickstoff nichtsubstituierten Amidoxime angewandt werden.IX. Mitteilung: Collect. czechoslov. chem. Commun. 24, 1720 (1959). — X. Mitteilung: Collect. czechoslov. chem. Commun. (im Druck).