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PubMed2000

Xylene monooxygenase catalyzes the multistep oxygenation of toluene and pseudocumene to corresponding alcohols, aldehydes, and acids in Escherichia coli JM101.

Xylene monooxygenase of Pseudomonas putida mt-2 catalyzes the methylgroup hydroxylation of toluene and xylenes. To investigate the potential of xylene monooxygenase to catalyze multistep oxidations of one methyl group, we tested recombinant Escherichia coli expressing the monooxygenase genes xylM and xylA under the control of the alk regulatory system of Pseudomonas oleovorans Gpo1. Expression of xylene monooxygenase genes could efficiently be controlled by n-octane and dicyclopropylketone. Xylene monooxygenase was found to catalyze the oxygenation of toluene, pseudocumene, the corresponding alcohols, and the corresponding aldehydes. For all three transformations (18)O incorporation provided stong evidence for a monooxygenation type of reaction, with gem-diols as the most likely reaction intermediates during the oxygenation of benzyl alcohols to benzaldehydes. To investigate the role of benzyl alcohol dehydrogenase (XylB) in the formation of benzaldehydes, xylB was cloned behind and expressed in concert with xylMA. In comparison to E. coli expressing only xylMA, the presence of xylB lowered product formation rates and resulted in back formation of benzyl alcohol from benzaldehyde. In P. putida mt-2 XylB may prevent the formation of high concentrations of the particularly reactive benzaldehydes. In the case of high fluxes through the degradation pathways and low aldehyde concentrations, XylB may contribute to benzaldehyde formation via the energetically favorable dehydrogenation of benzyl alcohols. The results presented here characterize XylMA as an enzyme able to catalyze the multistep oxygenation of toluenes.

Alcohols↗
PubMed1985

Aldehyde dehydrogenase activities in hepatocyte nodules and hepatocellular carcinomas from Wistar rats.

The activities of aldehyde dehydrogenases using benzaldehyde and propionaldehyde as substrates and NADP and NAD as coenzymes were determined in normal liver, hepatocyte nodules and hepatocellular carcinomas from male Wistar rats. Hepatocyte nodules were produced by intermittent exposure of rats to 0.05% 2-acetylaminofluorene or by initiation with diethylnitrosamine followed by selection using 2 weeks of dietary exposure to 0.02% 2-acetylaminofluorene and partial hepatectomy. The activities of propionaldehyde:NAD and benzaldehyde:NADP aldehyde dehydrogenases were increased in hepatocyte nodules of all types as well as in most hepatocellular carcinomas. The most prominent elevation of enzyme activity was found in the cytosol of persistent hepatocyte nodules (35-60 times) and some hepatocellular carcinomas (92 times) using benzaldehyde and NADP. The benzaldehyde:NADP aldehyde dehydrogenase activity varied considerably between different nodules suggesting the existence of a subpopulation of hepatocyte nodules with very high enzymatic activities. The activity of propionaldehyde:NAD aldehyde dehydrogenase activity as well as of gamma-glutamyltransferase did not show substantial internodular variations. The activity of benzaldehyde:NADP aldehyde dehydrogenase in individual carcinomas investigated in these experiments varied extensively. The data did not support the idea that all hepatomas had been developed from pre-neoplastic nodules with very high activity of this enzyme.

2-Acetylaminofluorene↗
PubMed1994

Biosynthetic Pathway for Veratryl Alcohol in the Ligninolytic Fungus Phanerochaete chrysosporium.

Veratryl alcohol (VA) is a secondary metabolite of white-rot fungi that produce the ligninolytic enzyme lignin peroxidase. VA stabilizes lignin peroxidase, promotes the ability of this enzyme to oxidize a variety of physiological substrates, and is accordingly thought to play a significant role in fungal ligninolysis. Pulse-labeling and isotope-trapping experiments have now clarified the pathway for VA biosynthesis in the white-rot basidiomycete Phanerochaete chrysosporium. The pulse-labeling data, obtained with C-labeled phenylalanine, cinnamic acid, benzoic acid, and benzaldehyde, showed that radiocarbon labeling followed a reproducible sequence: it peaked first in cinnamate, then in benzoate and benzaldehyde, and finally in VA. Phenylalanine, cinnamate, benzoate, and benzaldehyde were all efficient precursors of VA in vivo. The isotope-trapping experiments showed that exogenous, unlabeled benzoate and benzaldehyde were effective traps of phenylalanine-derived C. These results support a pathway in which VA biosynthesis proceeds as follows: phenylalanine --> cinnamate --> benzoate and/or benzaldehyde --> VA.

Journal Article↗
PubMed1985

Stability-indicating liquid chromatographic determination of etoposide and benzyl alcohol in injectable formulations.

Simple and specific assays for etoposide, related impurities, and benzyl alcohol, as well as its degradation product, benzaldehyde, in injectable formulations were developed using high-performance liquid chromatography (HPLC). Etoposide, benzyl alcohol, benzaldehyde, and four etoposide impurities were determined with a mobile phase containing 26% acetonitrile in pH 4.0 acetate buffer with methyl p-aminobenzoate as the internal standard. Two etoposide precursors were additionally determined using 60% acetonitrile in the mobile phase with biphenyl as the internal standard. The assays were run sequentially. The etoposide assay had a total variability of less than 1% (RSD) and a recovery from placebo of 99.4%. Mean recovery of impurity standards spiked at the 2% level relative to the etoposide level was 98%. Recoveries for benzyl alcohol and benzaldehyde were 100.5% and 102.2%, respectively. Absorbance ratios generated from samples and compared with undegraded standards demonstrated specificity for etoposide. Similar response regression equations with correlation coefficients greater than 0.99 were obtained for etoposide and four impurities over the 2-8 micrograms/mL concentration range, indicating that an etoposide standard could be used to quantitate low impurity levels down to 0.2% relative to the etoposide injectable concentration. Benzaldehyde could be reliably detected at concentrations down to 0.5 micrograms/mL, equivalent to 0.16% of the benzyl alcohol level.

Benzaldehydes↗
PubMed1997

Biotransformation for L-ephedrine production.

L-ephedrine is widely used in pharmaceutical preparations as a decongestant and anti-asthmatic compound. One of the key intermediates in its production is L-phenylacetylcarbinol (L-PAC) which can be obtained either from plants (Ephedra sp.), chemical synthesis involving resolution of a racemic mixture, or by biotransformation of benzaldehyde using various yeasts. In the present review, recent significant improvements in the microbial biotransformation are assessed for both fed-batch and continuous processes using free and immobilised yeasts. From previous fed-batch culture data, maximal levels of L-PAC of 10-12 gl-1 were reported with yields of 55-60% theoretical based on benzaldehyde. However, recently concentrations of more than 22 gl-1 have been obtained using a wild-type strain of Candida utilis. This has been achieved through optimal control of yeast metabolism (via microprocessor control of the respiratory quotient, RQ) in order to enhance substrate pyruvate production and induce pyruvate decarboxylase (PDC) activity. Processes involving purified PDC have also been evaluated and it has been demonstrated that L-PAC levels up to 28 gl-1 can be obtained with yields of 90-95% theoretical based on the benzaldehyde added. In the review the advantages and disadvantages of the various strategies for the microbial and enzymatic production of L-PAC are compared. In view of the increasing interest in microbial biotransformations, L-PAC production provides an interesting example of enhancement through on-line control of a process involving both toxic substrate (benzaldehyde) and end-product (L-PAC, benzyl alcohol) inhibition.

Acetone↗
PubMed1993

Free radical induction in the brain and liver by products of toluene catabolism.

Toluene and its metabolites have been studied with respect to their reactive oxygen species-enhancing potential in isolated systems and in vivo. The induction of reactive oxygen species (ROS) production was assayed using the probe 2',7'-dichlorodihydrofluorescin diacetate (DCFH-DA). Intraperitoneal injection of toluene, benzyl alcohol or benzaldehyde caused a significant elevation in the rate of ROS formation within hepatic mitochondrial fractions (P2). In the brain, only toluene induced ROS formation, while benzyl alcohol and benzaldehyde did not have any effect. Glutathione (GSH) levels were depressed in liver and brain regions from toluene-treated rats. However, no such depression was evident in brains treated with toluene metabolites. P2 fractions from phenobarbital-pretreated rats exhibited a heightened ROS response when challenged with toluene, in vitro. Pretreatment of rats in vivo with 4-methylpyrazole, an alcohol dehydrogenase inhibitor, or sodium cyanamide, an aldehyde dehydrogenase inhibitor, prior to exposure to toluene, caused a significant decrease and increase, respectively, in toluene-stimulated rates of ROS generation in the CNS and liver. Electron spin resonance spectroscopy, employing the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), was conducted. Incubation of the spin trap with P2 fractions and toluene or benzaldehyde elicited a spectrum corresponding to the hydroxyl radical. Incubation of benzaldehyde with aldehyde dehydrogenase produced a strong signal that was blocked completely by superoxide dismutase and inhibited partially by catalase, suggesting the presence of superoxide radicals and the involvement of the iron-catalyzed Haber-Weiss reaction leading to the production of hydroxyl radicals. Thus, ROS generation during toluene catabolism may occur at two steps: cytochrome P450 oxidation and aldehyde dehydrogenase oxidation. In addition, GSH may play an important role in protection against the induction of ROS generation in the CNS and liver following exposure to toluene.

Aldehyde Dehydrogenase↗
PubMed2005

Synthesis and anticancer activity of benzyloxybenzaldehyde derivatives against HL-60 cells.

A series of benzyloxybenzaldehyde derivatives were prepared and tested against the HL-60 cell line for anticancer activity. Preliminary structure-activity relationships were established. It was discovered that 2-(benzyloxy)benzaldehyde (17), 2-(benzyloxy)-4-methoxybenzaldehyde (26), 2-(benzyloxy)-5-methoxybenzaldehyde (27), 2-(benzyloxy)-5-chlorobenzaldehyde (28), 2-[(3-methoxybenzyl)oxy]benzaldehyde (29), 2-[(2-chlorobenzyl)oxy]benzaldehyde (30), and 2-[(4-chlorobenzyl)oxy]benzaldehyde (31) exhibited significant activity at 1-10 microM. Among them, compound 29 was the most potent one. The morphological assessment and DNA fragmentation analysis indicated that these compounds arrested cell cycle progression at G2/M phase and induced cell apoptosis. They resulted in the loss of mitochondrial membrane potential after 12h of treatment.

Antineoplastic Agents↗
PubMed2001

Interaction of human aldehyde dehydrogenase with aromatic substrates and ligands.

The substrate benzaldehyde (but not propionaldehyde) could elute aldehyde dehydrogenase from a p-hydroxyacetophenone-affinity column, and inhibit the esterase activity (K(i)=47 microM), indicating that this simple aromatic aldehyde binds to the free enzyme and possibly in the substrate-binding site. Thus, the kinetic mechanism for aldehyde dehydrogenase might be dependent upon which aldehyde is used in the reaction. Chloramphenicol which also elutes the enzyme from the affinity column, shows a discriminatory effect by inhibiting the ALDH1 oxidation of benzaldehyde and activating that of propionaldehyde while showing no effect when assayed with hexanal or cyclohexane-carboxaldehyde. Chloramphenicol is an uncompetitive inhibitor against NAD when benzaldehyde is the substrate. We propose that this drug might interact with both the benzaldehyde and NAD binding sites.

Aldehyde Dehydrogenase↗
PubMed2002

Serotonin mediates food-odor associative learning in the nematode Caenorhabditiselegans.

We demonstrate that Caenorhabditis elegans is able to form an association between the presence of the odorant benzaldehyde and the food content of its environment. When exposed to 100% benzaldehyde for 1 h in the absence of food the naive attractive response is reduced, and we have found that this olfactory adaptation is attenuated by the presence of food. Contrary to nonassociative (single stimulus) learning theory, this response is not a function of the total time of exposure to benzaldehyde but rather an associative function of the ability of benzaldehyde to predict a nutrient-deficient environment. Genetic and pharmacological evidence revealed that the effects of food in this learning paradigm are mediated by serotonergic signaling.

Adaptation, Physiological↗
PubMed2006

Identification of novel benzoylformate decarboxylases by growth selection.

A growth selection system was established using Pseudomonas putida, which can grow on benzaldehyde as the sole carbon source. These bacteria presumably metabolize benzaldehyde via the beta-ketoadipate pathway and were unable to grow in benzoylformate-containing selective medium, but the growth deficiency could be restored by expression in trans of genes encoding benzoylformate decarboxylases. The selection system was used to identify three novel benzoylformate decarboxylases, two of them originating from a chromosomal library of P. putida ATCC 12633 and the third from an environmental-DNA library. The novel P. putida enzymes BfdB and BfdC exhibited 83% homology to the benzoylformate decarboxylase from P. aeruginosa and 63% to the enzyme MdlC from P. putida ATCC 12633, whereas the metagenomic BfdM exhibited 72% homology to a putative benzoylformate decarboxylase from Polaromonas naphthalenivorans. BfdC was overexpressed in Escherichia coli, and the enzymatic activity was determined to be 22 U/ml using benzoylformate as the substrate. Our results clearly demonstrate that P. putida KT2440 is an appropriate selection host strain suitable to identify novel benzoylformate decarboxylase-encoding genes. In principle, this system is also applicable to identify a broad range of different industrially important enzymes, such as benzaldehyde lyases, benzoylformate decarboxylases, and hydroxynitrile lyases, which all catalyze the formation of benzaldehyde.

Amino Acid Sequence↗
PubMed2003

Transcriptional regulation of the gene encoding an alcohol dehydrogenase in the archaeon Sulfolobus solfataricus involves multiple factors and control elements.

A transcriptionally active region has been identified in the 5' flanking region of the alcohol dehydrogenase gene of the crenarchaeon Sulfolobus solfataricus through the evaluation of the activity of putative transcriptional regulators and the role of the region upstream of the gene under specific metabolic circumstances. Electrophoretic mobility shift assays with crude extracts revealed protein complexes that most likely contain TATA box-associated factors. When the TATA element was deleted from the region, binding sites for both DNA binding proteins, such as the small chromatin structure-modeling Sso7d and Sso10b (Alba), and transcription factors, such as the repressor Lrs14, were revealed. To understand the molecular mechanisms underlying the substrate-induced expression of the adh gene, the promoter was analyzed for the presence of cis-acting elements recognized by specific transcription factors upon exposure of the cell to benzaldehyde. Progressive dissection of the identified promoter region restricted the analysis to a minimal responsive element (PAL) located immediately upstream of the transcription factor B-responsive element-TATA element, resembling typical bacterial regulatory sequences. A benzaldehyde-activated transcription factor (Bald) that specifically binds to the PAL cis-acting element was also identified. This protein was purified from heparin-fractionated extracts of benzaldehyde-induced cells and was shown to have a molecular mass of approximately 16 kDa. The correlation between S. solfataricus adh gene activation and benzaldehyde-inducible occupation of a specific DNA sequence in its promoter suggests that a molecular signaling mechanism is responsible for the switch of the aromatic aldehyde metabolism as a response to environmental changes.

5' Flanking Region↗
PubMed2004

Monitoring plum curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), populations in apple and peach orchards in the mid-Atlantic.

We evaluated responses of plum curculio, Conotrachelus nenuphar (Herbst), to four trap types in commercial and unsprayed apple and peach orchards. Trap types included black pyramid and clear Plexiglas panel traps deployed outside the orchard 2 m from the border row, and branch-mimicking cylinder and trunk-mounted screen traps attached to trees in the border row. Bait treatments evaluated in conjunction with each trap type included the synthetic fruit volatile benzaldehyde, the aggregation pheromone grandisoic acid (GA), benzaldehyde in combination with GA, and an unbaited control treatment. In commercial apple orchards, significantly more plum curculio were captured in traps baited with benzaldehyde + GA compared with traps baited with other treatments. Furthermore, significantly more plum curculio were captured by screen traps baited with benzaldehyde + GA compared with unbaited control traps. Significantly more plum curculio were captured by screen traps compared with other trap types in an unsprayed apple orchard. Very few captures were recorded in commercial peach orchards. Dissections of trapped females indicate that bivoltine populations are present in the mid-Atlantic. In general, correlations between timing and amount of trap captures and timing and amount of fruit injury inflicted concurrently or 1 wk after trap captures were very weak for all trap types and bait combinations. Our results agree with previous studies in the northeastern United States in which trap captures are increased by presence of semiochemical baits but fail to serve as reliable tools to determine need for and timing of insecticide application against plum curculio.

Animals↗
PubMed2003

Kinetic behavior of Desulfovibrio gigas aldehyde oxidoreductase encapsulated in reverse micelles.

We report the kinetic behavior of the enzyme aldehyde oxidoreductase (AOR) from the sulfate reducing bacterium Desulfovibrio gigas (Dg) encapsulated in reverse micelles of sodium bis-(2-ethylhexyl) sulfosuccinate in isooctane using benzaldehyde, octaldehyde, and decylaldehyde as substrates. Dg AOR is a 200-kDa homodimeric protein that catalyzes the conversion of aldehydes to carboxylic acids. Ultrasedimentation analysis of Dg AOR-containing micelles showed the presence of 100-kDa molecular weight species, confirming that the Dg AOR subunits can be dissociated. UV-visible spectra of encapsulated Dg AOR are indistinguishable from the enzyme spectrum in solution, suggesting that both protein fold and metal cofactor are kept intact upon encapsulation. The catalytic constant (k(cat)) profile as a function of the micelle size W(0) (W(0)=[H(2)O]/[AOT]) using benzaldehyde as substrate showed two bell-shaped activity peaks at W(0)=20 and 26. Furthermore, enzymatic activity for octaldehyde and decylaldehyde was detected only in reverse micelles. Like for the benzaldehyde kinetics, two peaks with both similar k(cat) values and W(0) positions were obtained. EPR studies using spin-labeled reverse micelles indicated that octaldehyde and benzaldehyde are intercalated in the micelle membrane. This suggests that, though Dg AOR is found in the cytoplasm of bacterial cells, the enzyme may catalyze the reaction of substrates incorporated into a cell membrane.

Aldehyde Reductase↗
PubMed1992

Kinetic properties of the bovine corneal aldehyde dehydrogenase (BCP 54).

The major soluble protein of bovine cornea (BCP 54: bovine corneal protein 54 kDa) was isolated successively by gel filtration, anion-exchange chromatography and chromatofocusing. The amino acid sequence of a fragment of the purified BCP 54 obtained by lysyl-endopeptidase digestion showed marked homology with tumor-associated and 2,3,7,8-tetrachloro-dibenzo-p-dioxin-inducible aldehyde dehydrogenase (AIDH). From the high similarity of BCP 54 with tumor-associated AIDH in structural form, it is suggested that BCP 54 has AIDH activity. We confirmed a high AIDH activity of BCP 54 by immunoprecipitation using a mouse anti-BCP 54 monoclonal antibody followed by a spectrophotometric assay for AIDH activity. Next we demonstrated the unique properties of the purified BCP 54 as AIDH. The major isoelectric point is 6.41. BCP 54 preferentially oxidizes aromatic aldehyde such as benzaldehyde with NAD as coenzyme, but cannot oxidize phenylacetaldehyde. After heat treatment the AIDH activity is more stable with propionaldehyde-NAD than with benzaldehyde-NADP. With propionaldehyde-NAD the pH profile shows a broad plateau from pH 6-9 followed by a sharp rise up to pH 10. In contrast, with benzaldehyde-NADP there is a sharp optimum at pH 9.0. The activity with only benzaldehyde-NADP is inhibited by p-hydroxymercuribenzoate, but is not affected by disulfiram and diethylstilbestrol. So we suggested that BCP 54 is an AIDH with kinetic properties different from the rat tumor-associated AIDH.

Aldehyde Dehydrogenase↗
PubMed2003

A new protocol for the in situ generation of aromatic, heteroaromatic, and unsaturated diazo compounds and its application in catalytic and asymmetric epoxidation of carbonyl compounds. Extensive studies to map out scope and limitations, and rationalization of diastereo- and enantioselectivities.

A variety of metalated tosylhydrazone salts derived from benzaldehyde have been prepared and were reacted with benzaldehyde in the presence of tetrahydrothiophene (THT) (20 mol %) and Rh(2)(OAc)(4) (1 mol %) to give stilbene oxide. Of the lithium, sodium, and potassium salts tested, the sodium salt was found to give the highest yield and selectivity. This study was extended to a wide variety of aromatic, heteroaromatic, aliphatic, alpha,beta-unsaturated, and acetylenic aldehydes and to ketones. On the whole, high yields of epoxides with moderate to very high diastereoselectivities were observed. A broad range of tosylhydrazone salts derived from aromatic, heteroaromatic, and alpha,beta-unsaturated aldehydes was also examined using the same protocol in reactions with benzaldehyde, and again, good yields and high diastereoselectivities were observed in most cases. Thus, a general process for the in situ generation of diazo compounds from tosylhydrazone sodium salts has been established and applied in sulfur-ylide mediated epoxidation reactions. The chiral, camphor-derived, [2.2.1] bicyclic sulfide 7 was employed (at 5-20 mol % loading) to render the above processes asymmetric with a range of carbonyl compounds and tosylhydrazone sodium salts. Benzaldehyde tosylhydrazone sodium salt gave enantioselectivities of 91 +/- 3% ee and high levels of diastereoselectivity with a range of aldehydes. However, tosylhydrazone salts derived from a range of carbonyl compounds gave more variable selectivities. Although those salts derived from electron-rich or neutral aldehydes gave high enantioselectivities, those derived from electron-deficient or hindered aromatic aldehydes gave somewhat reduced enantioselectivities. Using alpha,beta-unsaturated hydrazones, chiral sulfide 7 gave epoxides with high diastereoselectivities, but only moderate yields were achieved (12-56%) with varying degrees of enantioselectivity. A study of solvent effects showed that, while the impact on enantioselectivity was small, the efficiency of diazo compound generation was influenced, and CH(3)CN and 1,4-dioxane emerged as the optimum solvents. A general rationalization of the factors that influence both relative and absolute stereochemistry for all of the different substrates is provided. Reversibility in formation of the betaine intermediate is an important issue in the control of diastereoselectivity. Hence, where low diastereocontrol was observed, the results have been rationalized in terms of the factors that contribute to the reduced reversion of the syn betaine back to the original starting materials. The enantioselectivity is governed by ylide conformation, facial selectivity in the ylide reaction, and, again, the degree of reversibility in betaine formation. From experimental evidence and calculations, it has been shown that sulfide 7 gives almost complete control of facial selectivity, and, hence, it is the ylide conformation and degree of reversibility that are responsible for the enantioselectivity observed. A simple test has been developed to ascertain whether the reduced enantioselectivity observed in particular cases is due to poor control in ylide conformation or due to partial reversibility in the formation of the betaine.

Journal Article↗
PubMed1999

Interactions between wine polyphenols and aroma substances. An insight at the molecular level.

Control of the organoleptic quality of wine or grape-derived beverages requires the study of the interactions between flavor volatiles and polyphenols. The influence of catechin and a wine highly condensed tannin fraction on the volatility of aroma substances was investigated using a dynamic headspace technique. In a hydroalcoholic solution, isoamyl acetate, ethyl hexanoate, and benzaldehyde appeared to be more retained than limonene at low catechin concentrations (0-5 g/L). The tannin fraction induced a slight decrease of benzaldehyde volatility and a salting out of limonene and had no effect on the two esters. Furthermore, investigations at the molecular level were conducted using (1)H NMR spectroscopy. Chemical shift changes registered upon addition of a ligand to a substrate kept at constant concentration allowed the determination of the dissociation constant in a 1:1 binding model. Complexation with catechin was evaluated to be similarly weak for benzaldehyde and the two esters. In addition, catechin and epicatechin displayed a higher affinity for benzaldehyde than for 3, 5-dimethoxyphenol, supporting the hypothesis of a hydrophobic driving force.

Algorithms↗
PubMed1999

N-Confused Tetraphenylporphyrin and Tetraphenylsapphyrin Formation in One-Flask Syntheses of Tetraphenylporphyrin.

The yields of tetraphenylporphyrin (TPP), N-confused tetraphenylporphyrin (NC-TPP), and tetraphenylsapphyrin (TPS) were examined under diverse conditions in the one-flask room-temperature reaction of pyrrole and benzaldehyde. The conditions examined included TFA and BF(3)-etherate catalysis, acid concentrations, pyrrole and benzaldehyde concentrations, pyrrole:benzaldehyde ratios, the addition of salt, and reaction times. The quantities of TPP, NC-TPP, and TPS were determined by HPLC. The yield of NC-TPP mirrored that of TPP during systematic variation of reaction parameters but was consistently lower (</=7.5%). The rate of NC-TPP formation also resembled that of TPP. Excess pyrrole was not required to form NC-TPP. About 2-fold more NC-TPP was obtained with BF(3)-etherate compared with TFA catalysis. TPS was observed in only a few of the reactions examined. The yield of TPS peaked early and declined well before the maximum yields of TPP and NC-TPP were reached. The highest yield of TPS observed was 1.2%. TPS was produced in higher yields by TFA compared with BF(3)-etherate catalysis. Additional pigments with chromatographic properties spanning the range of TPP and NC-TPP were observed in very low yield but were not characterized. N-confused tetramesitylporphyrin was isolated from the reaction of mesitaldehyde and pyrrole under BF(3)-ethanol cocatalysis. Examination of the Adler reaction of benzaldehyde and pyrrole revealed the presence of NC-TPP and TPS in the filtrate but not in the crystalline TPP material. The substantial chromatographic differences between the porphyrins and N-confused porphyrins make for straightforward isolation of the purified porphyrin devoid of contaminating N-confused porphyrin. These studies indicate that the scope of conditions yielding NC-TPP is extremely broad.

Journal Article↗
PubMed2000

Equilibrium constants between boron trifluoride etherate and carbonyl compounds in chloroform solution.

[reaction: see text] Equilibrium constants for boron trifluoride complexation with carbonyl compounds relative to diethyl ether were determined in CDCl(3). With benzaldehyde the equilibrium constant is 0.208. There is a 1.28-fold preference for BF(3) bonding to benzaldehyde-D over benzaldehyde-H. The rho(+) value for complexation with substituted benzaldehydes is -2.0. Equilibrium constants with cyclohexanone and isobutyraldehyde were found to be not very different from those predicted from the heats of addition of BF(3) relative to that for diethyl ether. The heats of addition can be correlated with Taft's beta values and with beta' values.

Journal Article↗