Tetramethyl Ester Research Articles

Syntheses of type-I porphyrins via monopyrrole tetramerization

Treatment of 2-[(N,N-dialkylamino)methyl]pyrrole-5-carboxylic acids (e.g. 10,12 or 11,13) in methanol with K 3Fe(CN) 6 gives type-I porphyrins (etioporphyrin-I 7, coproporphyrin-I tetramethyl ester 16, respectively); with pyrroles 10,12 the product 7 is contaminated with about 8% of other type-isomer(s).

Antineoplastic agents, 326. The stereochemistry of bastadins 8, 10, and 12 from the Bismarck archipelago marine sponge Ianthella basta.

An investigation of cancer cell-growth inhibitory constituents of the Papua New Guinea marine sponge Ianthella basta led to isolation of the C-6 hydroxybastadins 8 [1] 10 [2], and 12 [3]. The absolute stereochemistry (6S) of each bastadin (or its tetramethyl ester derivative) was determined by means of the Mosher-Trost method. Bastadins 10 [2] and 12 [3] were found to significantly inhibit the growth of a selection of human cancer cell lines. Bastadins 8, 10, and 12 inhibited growth of the Gram-positive opportunists Staphylococcus aureus and Enterococcus faecalis.

Characteristics of a europium-selective electrode based on a calix[4]arene tetraphosphine oxide

A poly(vinyl chloride)(PVC) electrode containing a calix[4]arene phosphine oxide [calix-(OCH2CH2POPh2)4] as the ionophore which is selective for EuIII in the presence of a high background of Na+ and other common ions is described. The selectivity and response of this electrode is compared with that of an electrode incorporating the tetramethyl ester calix[4]arene by injection experiments. Flow injection is also used to demonstrate the selectivity of the tetraphosphine oxide calix[4]arene for europium(III).

Autoassembling of cage structures

Treatment of alkylenebismalonates with NaH and benzoyl peroxide afforded dibenzoyloxy derivatives. Alkaline hydrolysis of the latter gave alkylenebistartronic acids. Tetramethyl and tetraethyl esters and tetraamides of these acids were synthesized

Die palladiumkatalysierte Cocyclisierung von Allenen mit elektronenarmen Alkinen. Einige Untersuchungen zur Kupplung von Allenderivaten mit Acetylendicarbonsäuredimethylester an Palladium und Platin

A diazadiene-stabilized palladacyclopentadiene acts as a catalyst precursor in the 2:2-cocyclisation of allene with acetylenedicarboxylic acid esters or 3-hexyne-2,5-dione to form 2,3,6,7-tetrasubstituted 1,4,5,8-tetrahydronaphthalenes at 60°C in high yields. These products can be oxidized quantitatively with 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ) to yield the 2,3,6,7-tetrasubstituted naphthalenes. Naphthalene-2,3,6,7-tetracarboxylic acid derivatives are interesting starting compounds for the preparation of thermally stable polyimides but difficult to obtain by conventional organic synthesis. Clasic organic multi-step procedures give yields only between 16% and 40% whereas our catalytic approach enables the formation of the tetramethyl ester in 82% yield following a simple two-step procedure. Allenic ethers even enable a one-pot synthesis (with lower yields) via catalyst-induced elimination of alcohol from an initially formed bis(alkoxy)-tetrahydronaphthalene. 4-Methylidene-palladacyclopent-2-enes can be trapped in stoichiometric reactions with allene derivatives (but not allene itself) and dimethyl acetylenedicarboxylate. Coupling of two allene moieties on platinum affords bis(methylidene)-metallacyclopentanes that might serve as model compounds for active palladium intermediates of the catalytic reaction. An unexpected open chain compound is obtained by insertion of phenoxyallene into the platinacyclopentadiene (RNCHCHNR) PtCECECEC E (E  COOCH 3), elimination and aromatization of the corresponding six-membered ring product.

Detection and characterization of fumonisin mycotoxins as their methyl esters by liquid chromatography/particle‐beam mass spectrometry

AbstractThe diazomethane‐derived tetramethyl esters of fumonisins can be introduced readily into mass spectrometers using flow injection analysis or liquid chromatography (LC) via a particle‐beam interface to yield chemical ionization and electron‐ionization spectra. The esters of fumonisins B1, B2, and B3 were well resolved on a C18 reversed‐phase column when eluted with a gradient of water + methanol + acetonitrile in the presence of 0.05% trifluoroacetic acid. Enhancement of analyte transport through the particle‐beam interface to afford increased ion abundances was achieved by addition of carriers. Polyfunctional amino acid carriers, such as L‐glutamic acid or L‐serine, effected at least 100‐fold increases in sensitivity. In the LC mode, post‐column addition of aqueous L‐serine was the most advantageous because background interference was limited to lower masses, and because of higher solubility, and ease of cleaning.

Time-resolved luminescence—pulse radiolysis determination of the fractions of porphyrin photosensitizer triplets giving rise to singlet excited oxygen on quenching by ground state triplet oxygen

By exploiting the different modes of excitation by ionizing radiation as opposed to light, a group of five porphyrin photosensitizer triplet excited states were formed free of the corresponding singlet excited states. Measurements were made of the corresponding triplet-induced singlet oxygen yields S Δ, with the aid of a recently developed technique for measuring the weak IR luminescence of singlet oxygen at 1270 nm generated by pulse radiolysis. The S Δ values obtained in C 6D 6 were 0.74, 0.75, 0.76, 0.88 and 0.92 for coproporphyrin III tetramethyl ester, deuteroporphyrin IX dimethyl ester, haematoporphyrin IX dimethyl ester, mesoporphyrin IX dimethyl ester and chlorophyll b respectively. This method for accurately measuring S Δ is generally applicable to triplet states with lifetimes of 10 μs or longer, provided that the parent photosensitizers react with singlet oxygen with rate constants of less than 10 8 M −1 s −1.

Enzymatic and chemical reactivities ofsym-monothiopyrophosphate

The synthesis of sym-monothiopyrophosphate (MTP) is described and the relative hydrolysis rate constants are reported for the dianion, trianion, and tetraanion in aqueous solution. The MTP-dianion undergoes hydrolysis at a rate 5 x 107-fold faster than the dianion of pyrophosphate (PPi) and the trianion undergoes hydrolysis 2.7 x 107-fold faster than PPi-trianion. The entropy of activation for the hydrolysis of MTP-trianion is 0.2 cal/deg/mol, and the enthalpy of activation is 19.7 kcal/mol. The hydrolysis appears to involve a dissociative transition state. The hydrolysis of the tetramethyl ester of MTP, in contrast, appears to involve an associative transition state. The Mg complex of MTP is a reasonable substrate for PPi-dependent phosphofructokinase and inorganic pyrophosphatase, despite its larger size relative to PPi. Therefore, MTP is tolerated within the active sites and in the transition states of enzymes that catalyze phosphoryl transfer from PPi to acceptor molecules. These observations are consistent with the transition states for these enzymes being dissociative in nature, although they do not prove that they are dissociative. MTP is, on the other hand, not a substrate for acetyl-CoA synthase, an enzyme that utilizes the Mg complex of PPi as a specific acceptor for the adenylyl group, an alkylphosphoryl group. Inasmuch as nonenzymatic reactions of this type involve associative transition states, it may be that the larger size of MTP relative to PPi undermines the catalytic process in the active site of acetyl-CoA synthase, which may catalyze adenylyl transfer through an associative transition state.

Electrochemical cyclization of tetramethyl esters of 2-substituted propane-1,1,3,3-tetracarboxylic acids in the presence of salts of hydrohalic acids

The chemical and electrochemical cyclization of tetramethyl esters of 2-substituted propane-1,1,3,3-tetracarboxylic acids in the presence of hydrohalic acid salt mediators were studied. It was found that the chemical variant of the cyclization of the corresponding α,α'-dianions of esters of propane-1,1,3,3-tetracarboxylic acids by the action of iodine or bromine is substantially inferior to the electrochemical variant. In the latter case, the esters of substituted cyclopopane-1,1,2,2-tetracarboxylic acids are formed in a 87–98% yield. The tetramethyl ester of 2-isopropylpropane-1,1,3,3-tetracarboxylic acid, which under the electrolysis conditions decomposes according to a Michael retroreaction is an exception.

1,2-DIHYDROXY-ETHANE-1,2-DIPHOSPHONIC ACID DERIVATIVES: STEREOCHEMICAL INVESTIGATIONS BY NMR METHODS

Abstract A variety of NMR spectroscopic methods has been used to investigate the stereochemistry of a series of derivatives of 1,2-dihydroxy-ethane-1,2-diphosphonic acid, a structural analogue of tartaric acid. These derivatives are prepared by diastereospecific reactions of P(O)H compounds with glyoxal. 1H, 13C, and 31P spectra using single and double resonance techniques have been measured for eight typical derivatives 1–8. In the case of the tetramethyl ester both diastereomers 2a and 2b were available, and they have been distinguished by measurement of coupling constants 3Jpp and 3 HH as well as by measuring the proton decoupled 31P NMR spectrum in the presence of a chiral additive, L(+)-dibenzoyltartaric acid. Both meso and racemic forms 2a and 2b have the two phosphonic acid groups in an anti-periplanar arrangement, as do all the other derivatives 1, 3–8 we have studied.

Electrochemical cyclization of the tetramethyl ester of propane-1,1,3,3-tetracarboxylic acid in the presence of salts of hydrogen halides

1. On electrolysis in methanol in the presence of the catalyst carrier NaI, tetramethyl propane-1,1,3,3-tetracarboxylate cyclizes with the exclusive formation of tetramethyl cyclopropane-1,1,2,2-tetracarboxylate with the yield up to 98%. 2. In the presence of NaBr and LiCl, hexamethyl pentane-1,1,3,3,5,5-hexacarboxylate, hexamethyl cyclopentane-1,1,2,2,4,4-hexacarboxylate, and tetramethyl tetrahydrofuran-2,2,4,4-tetracarboxylate are also formed; the last may be obtained with the yield up to 60%.

Catalytic inhibition of the radical polymerization of methyl methacrylate

In the polymerization of methyl methacrylate in the presence of chain transfer catalysts, i.e. cobalt complexes of macroheterocyclic compounds of the tetramethyl ester of hematoporphyrin (CoPo) and phthalocyanine (CoPh) and a CoPh + quinoline mixture polymerization retardation is observed, which increases in the series CoPo < CoPh < CoPh + quinoline. Not all the additives are used up, and the unused material can be separated unchanged at the end of the process. The stoichiometric inhibition factor determined from the kinetic data is much greater than 2, and in the case of the CoPh + quinoline system exceed 10 2. Chain termination catalysis on the cobalt complexes of the macroheterocyclic compounds is the most likely retardation mechanism.

ChemInform Abstract: Structure of “Dioneheme”. Total Synthesis of the Green Heme Prosthetic Group in Cytochrome cd1 Dissimilatory Nitrite Reductase.

AbstractIn order to investigate the structure of heme d1, a green substrate‐binding heme prosthetic group of cytochrome cd1, the metal‐free "dioneheme" tetramethyl ester (IV) is synthesized starting from the dialdehyde (I).

ChemInform Abstract: Synthetic and Biosynthetic Studies of Porphyrins. Part 9. Synthesis of Isocoproporphyrin, Dehydroisocoproporphyrin, and De‐ethylisocoproporphyrin.

AbstractThe title compounds as their tetramethyl esters (VIa) (isocoproporphyrin), (VIe) and (VIb), which are excreted by patients suffering from porphyria cutanea tarda or rats poisoned with hexachlorobenzene, are synthesized by the b‐oxobilane route.

Biosynthesis of the 1,3,4,6-hexanetetracarboxylic acid subunit of methanofuran

/sup 2/H- and /sup 13/C-labeled precursors were used to establish the pathway for the biosynthesis of the 1,3,4,6-hexanetetracarboxylic acid (TCA) component of methanofuran, which is found in some methanogenic bacteria. The extent and position of incorporation of label into TCA were measured from the mass spectrum of the tetramethyl ester of TCA that was prepared from methanofuran present in cells grown in the presence of labeled acetate. (2,2,2-/sup 2/H/sub 3/)Acetate was found to incorporate deuterium into two separate sites of the TCA molecule, with one on each side of the symmetrical molecule. One site was found to be labeled 37% with deuterium, the same as for the glutamic acid present in the cells; the other site was labeled 77% with deuterium, the same as for the malonate-derived compounds in the cells. An analog of TCA, 1-hydroxy-1,3,4,6-hexanetetracarboxylic acid, found in methanofuran isolated from Methanobrevibacter smithii, was found to incorporate /sup 13/C/sub 2/ units from (1,2-/sup 13/C/sub 2/)acetate into three positions of the molecule. One of the acetate /sup 13/C/sub 2/ units was incorporated into the non-hydroxyl-containing side of the molecule (carbons 4, 5, and 6 and the C-6 carboxylic acid group), and two acetate units were incorporated into the hydroxyl-containing sidemore » of the molecule (carbons 1, 2, and 3 and the C-1 carboxylic acid group). On the basis of this and additional information, it is concluded that TCA is biosynthesized by the condensation of ..cap alpha..-ketoglutaric acid with malonic acid to form 1,1,2,4-butanetetracarboxylic acid, which is further condensed with a second molecule of malonate, in a series of reactions analogous to those observed during fatty acid biosynthesis, to form TCA.« less

Synthetic and biosynthetic studies of porphyrins. Part 9. Synthesis of isocoproporphyrin, dehydroisocoproporphyrin, and de-ethylisocoproporphyrin

The title compounds, which were excreted by patients suffering from porphyria cutanea tarda or rats poisoned with hexachlorobenzene have been synthesized by the b-oxobilane route. Isocoproporphyrin tetramethyl ester (7a) was prepared from pyrromethanes corresponding to rings DA and BC of the macrocycle, and the de-ethyl analogue (7b) was prepared in a similar fashion; acetylation of the latter followed by reduction and dehydration then afforded dehydroisocoproporphyrin tetramethyl ester (7d). Minor by-products arising in the syntheses have been shown to arise by rearrangement of the BC pyrromethane.

Determination of ethylenediaminetetra-acetic acid in aqueous rinses of detergent-washed rubber stoppers of pharmaceutical vials using solid-phase extraction and capillary gas chromatography

A fused silica capillary gas chromatographic method is presented for the determination of traces of ethylenediaminetetra-acetic acid (EDTA) in aqueous rinses of rubber stoppers of pharmaceutical vials after treatment with detergents containing EDTA. Isolation and enrichment of EDTA from the aqueous medium is achieved using a commercially available strong anion-exchange solid-phase extraction cartridge, transformed to the formate form. A 2.0-ml volume of methanolic HCl is used for both elution of EDTA from the extraction column and formation of the tetramethyl ester derivative. With the incorporation of a methanolic wash to eliminate interfering components prior to elution with methanolic HCl, a limit of detection of 25 ng EDTA per ml water with a non-selective flame ionization detector is possible.

Relative reactivities of tetraalkyl esters of methylene bisphosphonic acid

The synthesis in high yield of tetraisopropyl esters of C-alkylated methylene bisphosphonic acids can be achieved by the alkylation of the thallium salts of tetraisopropyl esters of the parent methylene biphosphonic acids. Yields of C-alkylated products are markedly reduced when the tetraethyl or tetramethyl esters are used in this reaction. From a study of the 13C and 31P NMR spectra of the methylene bisphosphonates and their anions, this difference in reactivity is ascribed to steric factors.

The effect on photohaemolysis of variation in the structure of the porphyrin photosensitizer.

A comparison of the photosensitizing ability of a variety of porphyrins for photohaemolysis gives the following order of activity: protoporphyrin greater than deuteroporphyrin, mesoporphyrin, haematoporphyrin dimethyl ester much greater than haematoporphyrin diacetate, haematoporphyrin greater than haematoporphyrin monoacetate, coproporphyrin III, haematoporphyrin derivative, coproporphyrin III tetramethyl ester greater than uroporphyrin I, meso-tetra-(N-methyl-4-pyridinium)porphyrin tetratoluene-p-sulphonate, meso-tetra-(p-carboxyphenyl)porphyrin, protoporphyrin dimethyl ester, meso-tetra-(p-hydroxy-sulphonylphenyl)porphyrin tetrasodium salt, uroporphyrin III, deuteroporphyrin-3,8-disulphonic acid and protohaemin. The results for the metal-free porphyrins are rationalized in terms of solubility and partition properties, and a model is proposed for the incorporation of amphipathic porphyrins into the membrane lipid bilayer. Experiments with erythrocytes from patients with erythropoeitic protoporphyria and with normal erythrocytes to which porphyrin was added in a deuterium oxide medium do not lead to an increase in the rate of photohaemolysis. A possible explanation for this somewhat surprising observation is outlined.

Dealkylation during electron impact mass spectrometric analysis ofN- monoalkylated porphyrin methyl esters

The N-monoethylated, N-monoethylated and N-mono-1-propylated homologues of mesoporphyrin IX dimethyl ester and the corresponding methylated and 1-propylated homologues of coproporphyrin III tetramethyl ester have been prepared. Substituted porphyrins in a series could be distinguished from each other and from the parent porphyrin by their dication absorption spectra. All compounds gave molecular ions of varying intensities during electron impact mass spectrometry but thermal N-dealkylation to mesoporphyrin IX or coproporphyrin III methyl esters occurred readily and it was difficult to obtain spectra not showing fragmentation ions derived from this process. The compounds serve as models for the ‘green pigments’ produced in vivo by the action of some drugs and illustrate the problem of dealkylation during their analysis by electron impact mass spectrometry.