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At least 37 records · Page 2Linked to original sources
PubMed2001

Is the tert-butyl chloride solvolysis the most misunderstood reaction in organic chemistry? Evidence against nucleophilic solvent participation in the tert-butyl chloride transition state and for increased hydrogen bond donation to the 1-adamantyl chloride solvolysis transition state.

Despite theoretical calculations to the contrary, it has been argued that the 1-adamantyl cation is more stable than the tert-butyl cation in media of high dielectric constant. This argument has been utilized to suggest that the higher rate of solvolysis of tert-butyl chloride in aqueous ethanol is evidence for nucleophilic solvent participation in this classic reaction. Further, in "more highly ionizing" solvents, the rate of 1-adamantyl chloride is nearly the same as that of tert-butyl chloride, which is interpreted as a manifestation of the relative stabilities of the cations. However, the evidence cited does not explain the increased sensitivity of the rate of solvolysis of 1-adamantyl chloride over tert-butyl chloride to solvents which are better able to donate hydrogen bonds. The hypothesis developed here is that 1-adamantyl chloride solvolysis is assisted by hydrogen bond donation departing chloride ion to a greater extent than that of tert-butyl chloride solvolysis, most likely due to lessened steric interactions in a developing pyramidal cation. This hypothesis is supported by multiparameter solvent effect factor analyses utilizing the KOMPH2 equation which, in addition, quantifies the important role of ground-state destabilization due to strong solvent-solvent interactions. An important result from the good correlation of free energies of transfer of the tert-butyl chloride solvolysis transition state is that there is no change in mechanism, and, in particular, no nucleophilic participation even in non-hydroxylic basic solvents. The equation is also applied to the case of dimethylsulfonium ion solvolyses where the tert-butyl salt reacts substantially faster than the 1-adamantyl salt in ethanol and the gas phase. The decreased rate of the former in hydrogen bond donating solvents relative to the gas phase is as yet unclear. Solvent N values that were generated to characterize solvent nucleophilicity are shown not to be correlated by measures of solvent basicity but rather by the negative of measures of solvent hydrogen bond donor ability.

Journal Article↗
PubMed1999

Biotransformation of [(12)C]- and [(13)C]-tert-amyl methyl ether and tert-amyl alcohol.

tert-Amyl methyl ether (TAME) is intended for use as a gasoline additive to increase oxygen content. Increased oxygen content in gasoline reduces tailpipe emissions of hydrocarbons and carbon monoxide from cars. Due to possible widespread use of TAME, the toxicity of TAME is under investigation. We studied the biotransformation of TAME in rats and one human volunteer after inhalation of (12)C- or (13)C-labeled TAME. In addition, the biotransformation of [(13)C]-tert-amyl alcohol was studied in rats after gavage. Urinary metabolites were identified by GC/MS and (13)C NMR. Rats (two males and two females) were individually exposed to 2000 ppm [(12)C]- or [(13)C]TAME for 6 h, and urine was collected for 48 h. Free and glucuronidated 2-methyl-2,3-butanediol and a glucuronide of tert-amyl alcohol were identified by (13)C NMR, GC/MS, and LC/MS/MS as major urinary metabolites on the basis of the relative intensities of the (13)C NMR signals. The presence of several minor metabolites was also indicated by (13)C NMR; they were identified as tert-amyl alcohol, 2-hydroxy-2-methylbutyric acid, and 3-hydroxy-3-methylbutyric acid. One human volunteer was exposed to an initial concentration of 27 000 ppm [(13)C]TAME by inhalation for 4 min from a 2 L gas sampling bag, and metabolites of TAME excreted in urine were analyzed by (13)C NMR. All TAME metabolites identified in rats were also present in the human urine samples. To study tert-amyl alcohol biotransformation, male rats (n = 3) were treated with 250 mg/kg [(13)C]-tert-amyl alcohol dissolved in corn oil by gavage, and urine was collected for 48 h. (13)C NMR of the urine samples showed the presence of metabolites identical to those in the urine of [(13)C]TAME-treated rats. Our results suggest that TAME is extensively metabolized by rats and humans to tert-amyl alcohol which may be further oxidized to diols and carboxylic acids. These reactions are likely mediated by cytochrome P450-dependent oxidations.

Administration, Inhalation↗
PubMed2006

[Bis(trimethylsilyl)amido-kappaN]{tert-butyl[(E)-2-(tert-butylimino)ethyl]amido-kappa(2)N,N'}tin(II), a key intermediate in the synthesis of 1,3-di-tert-butyl-2,3-dihydro-1H-1,3,2-diazastannole.

The title compound, [Sn(C10H21N2)(C6H18NSi2)], contains the Sn(II) centre in a trigonal-pyramidal geometry. The basal plane is formed by three N atoms and the fourth apical position is occupied by a stereoactive lone pair. The Sn atom is displaced from the plane of the three N atoms by 1.1968 (12) A. The Sn-N bonds are highly polarized toward the N atoms, as confirmed by natural bonding orbital analysis.

Journal Article↗
PubMed1992

Formation of the semiquinone anion radical from tert-butylquinone and from tert-butylhydroquinone in rat liver microsomes.

The tert-butylsemiquinone anion radical is formed from tert-butylhydroquinone and from tert-butylquinone in rat liver microsomes. In the presence of oxygen, the quinone and, less extensively, the hydroquinone induce excess production of superoxide in microsomes. It is concluded that autoxidation of the semiquinone formed from the quinone by microsomal enzyme activity is responsible for superoxide formation and that the hydroquinone enters the redox cycle via autoxidation. tert-Butylquinone induces injury of the hepatocyte plasma membrane. tert-Butylhydroquinone and tert-butylquinone are metabolites of the antioxidant butylated hydroxyanisole. The semiquinone-dependent superoxide formation may contribute to the toxic actions of butylated hydroxyanisole.

Animals↗
PubMed1996

Glutathione conjugates of tert-butyl-hydroquinone, a metabolite of the urinary tract tumor promoter 3-tert-butyl-hydroxyanisole, are toxic to kidney and bladder.

3-tert-Butyl-4-hydroxyanisole and tert-butyl-hydroquinone (TBHQ) are antioxidants known to promote renal and bladder carcinogenesis in the rat, although the mechanisms of these effects are unclear. Because glutathione (GSH) conjugates of a variety of hydroquinones are nephrotoxic, and because 2-tert-butyl-5-(glutathion-S-yl)hydroquinone [5-(GSyl)TBHQ], 2-tert-butyl-6-(glutathion-S-yl)hydroquinone [6-(GSyl)TBHQ], and 2-tert-butyl-3,6-bis-(glutathion-S-yl)hydroquinone [3,6-bis-(GSyl)-TBHQ] have been identified recently as metabolites of TBHQ in the male rat, we investigated the effects of these metabolites in the male rat. At the highest dose tested (400 micromol/kg,i.v.) 5-(Gsyl)TBHQ and 6-(GSyl)TBHQ caused 2-fold increases in the urinary excretion of gamma-glutamyl transpeptidase and alkaline phosphatase, and pigments arising from the polymerization of metabolites were deposited in the kidney. 3,6-bis-(GSyl)TBHQ (200 micromol/kg) was the most potent of the GSH conjugates tested and produced significant increases in the urinary excretion of gamma-glutamyl transpeptidase, alkaline phosphatase, lactate dehydrogenase, and glucose (2-, 2-, 22-, and 11-fold increases, respectively). Alterations in the biochemical parameters correlated with the degree of single cell and tubular necrosis in the S(3)-M segment of the proximal tubule, as observed by light microscopy. In addition to nephrotoxicity, 3,6-bis-(GSyl)TBHQ increased the bladder wet weight 2-fold and caused severe hemorrhaging of the bladder. The half-wave oxidation potentials of 5-(Gsyl)TBHQ and 6-(GSyl)TBHQ were similar to that of TBHQ, whereas the half-wave oxidation potential of 3,6-bis-(Gsyl)TBHQ was approximately 100 mV higher than that of TBHQ. The TBHQ-GSH conjugates also catalyzed the formation of 8- hydroxydeoxyguanosine, indicating that GSH conjugation does not impair the redox activity of TBHQ. Because some chemicals may induce carcinogenesis by a mechanism involving cytotoxicity followed by sustained regenerative hyperplasia, our results suggest that the toxicity of GSH conjugates of TBHQ to kidney and bladder may contribute to the promoting effect of 3-tert-butyl-4-hydroxyanisole and TBHQ in these tissues.

Animals↗
PubMed2000

Ligand substitution reactions of W6S8L6 with tricyclohexylphosphine (L = 4-tert-butylpyridine or n-butylamine): 31P NMR and structural studies of W6S8(PCy3)n(4-tert-butylpyridine)6-n (0 < n < or = 6) complexes.

The substitution reactions by bulky tricyclohexylphosphine (PCy3) ligands on W6S8L6 (L = 4-tert-butylpyridine or n-butylamine) clusters were investigated to prepare clusters with mixed axial ligands for low-dimensional cluster linking. When 4-6 equiv of PCy3 are used to react with W6S8(4-tert-butylpyridine)6 (4) in THF, cis-W6S8(PCy3)4(4-tert-butylpyridine)2 (1) is preferentially formed. But when starting with W6S8(n-butylamine)6 (2), only W6S8(PCy3)6 (3) is produced with 6 equiv of PCy3. Other conditions with fewer equivalents of PCy3 led to mixtures of partially substituted complexes in the W6S8L6-n(PCy3)n (0 < or = n < or = 6, L = 4-tert-butylpyridine or n-butylamine) series. A significantly distorted structure for 1 helps to explain its preferential formation. 1H NMR spectra were collected for clusters 1 and 2 and 31P NMR spectra for 1 and W6S8(4-tert-butylpyridine)6-n(PCy3)n complexes. P-P coupling through P-W-W-P is reported for the first time in octahedral metal clusters and shown to be very useful in identifying nearly all the W6S8L6-n(PR3)n complexes and their stereoisomers in the mixtures even before individual species are isolated.

Journal Article↗
PubMed2005

Syntheses of stable N-tert-alkoxyarylaminyl mono- and diradicals by the reaction of the lithium salts of 2,4,6-trisubstituted anilines with tert-alkyl mono- and diperoxybenzoates.

[reaction: see text] The reaction of the lithium salts of 2,4,6-triaryl- and 2-tert-butyl-4,6-diarylanilines with tert-alkyl mono- and diperoxybenzoates gave isolable N-tert-alkoxyarylaminyl mono- and diradicals. The substituent effects of tert-alkyl peroxybenzoates on the yields of N-tert-alkylarylaminyls were studied.

Journal Article↗
PubMed2000

Tyrosinase-mediated formation of a reactive quinone from the depigmenting agents, 4-tert-butylphenol and 4-tert-butylcatechol.

Exposure of the skin to certain phenols or catechols such as 4-tert-butylphenol (TBP) and 4-tert-butylcatechol (TBC) may cause leukoderma. These substances are used in the polymer industry and numerous cases have been reported. Several theories of the mechanism for chemical leukoderma have been suggested. In the present study, TBP and TBC are shown to be oxidised by tyrosinase. The oxidation of TBC yields a quinone that is further investigated on its reactions with cysteine or glutathione (GSH). The products formed are isolated and identified by mass spectrometry and nuclear magnetic resonance as being 4-tert-butyl-6-S-cysteinylcatechol (cys-TBC) and 4-tert-butyl-6-S-glutathionylcatechol (GS-TBC). The reactive quinone is a strongly electrophilic substance that rapidly reacts with GSH. A depletion of the GSH defence system may give conditions where the quinone lives long enough to effect its toxic properties. The influence of the reactive tert-butylquinone on enzymatic activities is demonstrated by the inhibition of glyceraldehyde-3-phosphate dehydrogenase.

Agaricales↗
PubMed2001

The molecular and crystal structure of tert-butyl Nalpha-tert-butoxycarbonyl-L-(S-trityl)cysteinate and the conformation-stabilizing function of weak intermolecular bonding.

The title compound, C31H37NO4S [systematic name: (R)-tert-butyl-2-[(tert-butoxycarbonyl)amino]-3-(tritylsulfanyl)propanoate] is an L-cysteine derivative with three functions: NH2, COOH and SH, blocked by protecting groups tert-butoxycarbonyl, tert-butyl and trityl, respectively. The main chain of the molecule adopts the extended, nearly all-trans C5 conformation with the intramolecular N-H...O=C hydrogen bond. The urethane group is not involved in any intermolecular hydrogen bonding. Only weak intermolecular hydrogen bonds and hydrophobic contacts are observed in the crystal structure. These are C-H...O hydrogen bonds and CH/pi interactions with donor...acceptor distances, C...O ca. 3.5 A and C...C ca. 3.7 A, respectively. The first type of interaction links phenyl H-atoms and carbonyl groups. The second type of interaction is formed between a methyl group of the tert-butyl fragment and a trityl phenyl ring. The resulting molecular conformation in the crystal is very close to an ab initio minimum energy conformer of the isolated molecule. The extended C5 conformation of the main peptide chain is the same and there is slight discrepancy in the disposition of trityl phenyl rings. Their small dislocation creates the possibility of forming the entire network above of extensive, specific, weak intermolecular interactions; these constrain the molecule and permit it to retain the minimum energy C5 conformation of its main chain in the solid state. In contrast, in n-hexane solution, where such specific interactions cannot occur, only a small population of the molecules adopts the extended C5 conformation.

Crystallography, X-Ray↗
PubMed1985

Metabolism of 3-tert-butyl-4-hydroxyanisole to 3-tert-butyl-4,5-dihydroxyanisole by rat liver microsomes.

3-tert-Butylhydroxyanisole (3-BHA) is an antioxidant which can have a modulating effect on chemical carcinogenesis. Information concerning the metabolism of 3-BHA is incomplete. In the present study, the metabolites formed by incubating 3-BHA with liver microsomes from rats given beta-naphthoflavone by p.o. intubation were studied. Three metabolites were identified, two major metabolites and a minor metabolite. One of the major metabolites was the catechol of 3-BHA, i.e., 3-tert-butyl-4,5-dihydroxyanisole, which has not previously been reported. A characteristic of this compound is its capacity to be oxidized readily. The second major metabolite was tert-butyl hydroquinone which has been reported previously to be a liver microsomal metabolite of 3-BHA. The third metabolite, which occurred in small quantities, was 2,2'-dihydroxy-3,3'-di-tert-butyl-5,5'-dimethoxydiphenyl. 2,2'-Dihydroxy-3,3'-di-tert-butyl-5,5'-dimethoxydiphenyl has been identified previously as a major metabolite of 3-BHA in the rat intestine. An understanding of the metabolism of 3-BHA may assist in elucidating the mechanism(s) of its biological effects.

Animals↗
PubMedDate not supplied

Measurement of methyl tert-butyl ether and tert-butyl alcohol in human blood by purge-and-trap gas chromatography-mass spectrometry using an isotope-dilution method.

We developed an isotope-dilution method for measuring methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) in whole human blood using a purge-and-trap gas chromatographic-mass spectrometric method. The labeled analogues for MTBE and TBA were [2H12]methyl tert-butyl ether and [2H9]-tert-butyl alcohol, respectively. Volatiles were removed from the blood by direct helium purging of the liquid; were trapped on a Tenax trap; and were desorbed, cryofocused, and chromatographed on a DB-624 capillary column that was connected directly to the ion source of a mass spectrometer. Detection was by mass analysis using a double-focusing magnetic-sector mass spectrometer operating in the full-scan mode at the medium mass resolution of 3000. For the isotope-dilution method, the minimum detection limits in blood (5-10 mL) are 0.01 microgram/L for MTBE and 0.06 microgram/L for TBA. The isotope-dilution method proved to be a big improvement in recovery, reproducibility, and sensitivity over our previous analytical method, which used the labeled ketone, [4-2H3]-2-butanone, as the internal standard for both MTBE and TBA. The isotope-dilution method has sufficient sensitivity for monitoring blood levels of MTBE and TBA in populations exposed to oxygenated fuels containing MTBE.

Butanols↗
PubMedDate not supplied

Synthesis of 5-tert-butyl-1-(3-tert-butyldimethylsiloxy)phenyl-4,4-dimethyl-2,6,7-trioxabicyclo[3.2.0]heptanes and their fluoride-induced chemiluminescent decomposition: effect of a phenolic electron donor on the CIEEL decay rate in aprotic polar solvent.

Four bicyclic dioxetanes bearing a phenolic substituent, 3-tert-butyldimethylsiloxy-4-chlorophenyl (3a), 5-tert-butyldimethylsiloxy-4-chloro-2-ethylphenyl (3b), 5-tert-butyldimethylsiloxy-2-ethylphenyl (3c), and 3-tert-butyldimethylsiloxy-4-ethylphenyl (3d), were synthesized. All dioxetanes 3a-3d gave intense blue light on treatment with tetrabutylammonium fluoride (TBAF) in DMSO or acetonitrile. Kinetic study on the fluoride-induced CIEEL decay of these dioxetanes 3a-3d and the parent dioxetane 2b revealed that the para-substitution with chlorine on the phenolic moiety of dioxetane increases free energy of activation (DeltaG++), while the para-substitution with ethyl on the aryl decreases DeltaG++. On the other hand, substitution with an ethyl at the ortho-position instead of the para-position was found to increase DeltaG++ and to suppress the CIEEL decay. This fact is attributed to the steric factor of the ortho-ethyl group which would prevent the aromatic ring from rotating freely around the axis joined to the peroxide ring, and supports the suggestion for a CIEEL-active dioxetane bearing a phenolic moiety that an intramolecular electron transfer occurs preferentially from the phenolic donor to O-O of the dioxetane ring, when the aromatic ring lies in a certain conformation(s).

Electrons↗
PubMed1999

Purification and some properties of two enzymes from rat liver cytosol that catalyze carbonyl reduction of 6-tert-butyl-2, 3-epoxy-5-cyclohexene-1,4-dione, a metabolite of 3-tert-butyl-4-hydroxyanisole.

6-tert-Butyl-2,3-epoxy-5-cyclohexene-1,4-dione (TBE), a metabolite of 3-tert-butyl-4-hydroxyanisole, was converted to 6-tert-butyl-2, 3-epoxy-4(R)-hydroxy-5-cyclohexen-1-one ((4R)-TBEH) and 6-tert-butyl-2,3-epoxy-4(S)-hydroxy-5-cyclohexen-1-one ((4S)-TBEH) by TBE-reducing enzymes in rat liver cytosol. Two TBE-reducing enzymes (TBE-R1 and TBE-R2) were purified 18- and 117-fold, respectively, to apparent homogeneity from rat liver cytosol using DEAE-Sephacel, Blue Sepharose CL-6B, hydroxylapatite, and Sephadex G-100 column chromatography. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that both enzymes were monomeric. The purified TBE-R1 and TBE-R2 had molecular weights of 37 and 35 kDa and isoelectric points of 6.5 and 5.8, respectively. Both enzymes had an optimum pH of about 5.5 with TBE as substrate. TBE-R1 utilized NADH or NADPH equally as cofactor, and the Km values of NADH and NADPH for TBE with TBE-R1 were estimated to be 15 and 29 microM, respectively. On the other hand, TBE-R2 specifically utilized NADPH and the Km value for TBE was estimated to be 92 microM in the presence of NADPH. Both enzymes reduced aromatic aldehydes, ketones, and quinones at higher rates. In addition, TBE-R2 reduced and oxidized 3-ketosteroids at a higher rate in the presence of NAD(H) and/or NADP(H). Both enzyme activities were inhibited by quercitrin or p-chloromercuribenzoic acid, but little inhibition was observed with phenobarbital or pyrazole. Dicoumarol inhibited significantly TBE-R1 activity but not TBE-R2 activity. In the conversion of TBE to TBEH, TBE-R1 preferentially reduced TBE to (4R)-TBEH, whereas TBE-R2 preferred the reduction of TBE to (4S)-TBEH.

Alcohol Oxidoreductases↗
PubMed1998

Exposure of gasoline road-tanker drivers to methyl tert-butyl ether and methyl tert-amyl ether.

Organic oxygenates, namely, methyl tert-butyl ether (MTBE) and methyl tert-amyl ether (MTAE), are added to gasoline to reduce carbon monoxide in exhausts and to enhance the octane number. The aim of this study was to investigate road-tanker drivers' exposure to oxygenate vapors during road-tanker loading and unloading as well as to evaluate the measurements of these ethers and their metabolites in the urine as a means of assessing the uptake of the ethers. A total of 11 drivers in different parts of Finland were trained to monitor their exposure with personal samplers, to report their working conditions, and to collect their whole-day urine samples. Charcoal tubes of the air samples were analyzed for MTBE, MTAE, benzene, toluene, and aliphatic hydrocarbons. For biological monitoring purposes the two main oxygenates, tertiary ethers MTBE and MTAE, as well as their main metabolites, tertiary alcohols tert-butanol (TBA) and tert-amyl alcohol (TAA), were determined in urine specimens. On average the drivers were exposed to vapors for short periods (21 +/- 14 min) three times during a work shift. The mean concentrations of MTBE and MTAE (mean +/- SD) were 8.1 +/- 8.4 and 0.3 +/- 0.4 mg/m3. The total MTBE uptake during the shift was calculated to be an average of 106 +/- 65 mumol. The mean concentrations of MTBE, TBA, MTAE and TAA detected in the first urine after the work shift were 113 +/- 76, 461 +/- 337, 16 +/- 21, and 40 +/- 38 nmol/l, and those found the next morning, 16 h later, were 18 +/- 12, 322 +/- 213, 9 +/- 10, and 20 +/- 27 nmol/l. The good relationship (r = 0.84) found between MTBE exposure and postshift excretion suggests that urinary MTBE can be used for biological monitoring of exposure, but at the present low level of exposure the corresponding metabolite TBA is not equally reliable. The determination of MTAE and its metabolite TAA in urine is sensitive enough to detect the low degree of exposure to MTAE, but in this study the data were too scarce to allow calculation of the correlations due to very low levels of MTAE exposure.

Adult↗
PubMed1998

Exposure to methyl tert-butyl ether and tert-amyl methyl ether from gasoline during tank lorry loading and its measurement using biological monitoring.

OBJECTIVE AND METHODS: The exposure of Finnish tank lorry drivers to methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) during loading of gasoline was studied using biological and breathing-zone sampling. During the field measurements in October 1994 and August 1995 the gasolines (95, 98, 99 RON) contained MTBE to 5.2-11.8% and TAME to 0-6%. RESULTS: The geometric mean (GM) breathing-zone concentration of MTBE was 4.3 mg/m3 (n = 15) in October and 6.4 mg/m3 (n = 20) in August. The GM concentration of TAME, measured only in August, was 0.98 mg/m3. The mean loading/sampling times were 37 and 35 min, the mean wind speeds were 0.8 and 0.6 m/s, and the mean air temperatures were -4.9 degrees and + 14.1 degrees C, respectively. Blood samples collected on average at 20 min after gasoline loading/exposure showed an MTBE concentration of 143 nmol/l (GM, n = 14) in October and 213 nmol/l (GM, n = 20) in August. Pearson's coefficient of correlation (r) between the MTBE breathing-zone concentrations and MTBE in blood was 0.86 (P = 0.0001) in October and 0.81 (P = 0.00001) in August. No correlation was found between MTBE in air and the metabolite tert-butanol (TBA) in blood. MTBE, but not TBA, in urine samples collected on average at 2.5 h after exposure showed a correlation with MTBE in air. The concentrations of TAME and its metabolite tert-amyl alcohol were below the quantitation limits ( < 7 and < 100 nmol/l, respectively) in most blood and urine samples. CONCLUSIONS: The breathing-zone measurements showed low levels of exposure to the two oxygenates, the concentrations being well below the current hygienic standards for MTBE (250-360 mg/m3 for 15 min and 90-180 mg/m3 for 8 h). The linear correlations obtained for MTBE suggest that MTBE in blood or urine can be adopted as a valid biological exposure index.

Air Pollutants↗
PubMed2000

Crystal structures of heptakis(2,6-di-O-tert-butyldimethylsilyl)cyclomaltoheptaose, heptakis(2-O-methyl-3,6-di-O-tert-butyldimethylsilyl)cyclomaltoheptaose and heptakis(2-O-methyl)cyclomaltoheptaose.

Crystal structures of heptakis(2,6-di-O-tert-butyldimethylsilyl)cyclomaltoheptaose, heptakis(2-O-methyl-3,6-di-O-tert-butyldimethylsilyl)cyclomaltohep taose and heptakis(2-O-methyl)cyclomaltoheptaose were determined from X-ray diffraction patterns obtained for single crystals of the title compounds grown from ethyl acetate and ethanol, respectively, as solvent. The crystal structures prove conclusively that quantitative migration of the tert-butyldimethylsilyl group from the 2-O- to the 3-O-position [D. Icheln, B. Gehrcke, Y. Piprek, P. Mischnick, W.A. Konig, M.A. Dessoy, A.F. Morel, Carbohydr. Res., 280 (1996) 237-250] was achieved during methylation of heptakis(2,6-di-O-tert-butyldimethylsilyl)cyclomaltoheptaose by iodomethane-sodium hydride.

Crystallography↗
PubMed1999

Demonstration of the contact sensitizer p-tert-butylcatechol in p-tert-butylphenol formaldehyde resin.

BACKGROUND: In regard to patients hypersensitive to p-tert-butylphenol formaldehyde resin (PTBP-F-R), it is for diagnostic, therapeutic, and preventive reasons necessary to know the identity of the primary sensitizing substances and their sensitizing capacities, as well as their cross-reaction patterns. In patients hypersensitive to PTBP-F-R, we have demonstrated a statistically significant overrepresentation of simultaneous reactions to p-tert-butylcatechol (PTBC). In the guinea pig, we have shown that PTBC is a strong sensitizer, giving cross reactions to p-tert-butylphenol. Furthermore, PTBC cross reacts to the PTBP-F-R monomer 2,6-methylol p-tert-butylphenol, which is a strong sensitizer in the guinea pig. OBJECTIVE: The aim of this study was to investigate the background to the observed simultaneous reactions to PTBP-F-R and PTBC and to see if these could be explained by the presence of PTBC in PTBP-F-R. METHODS: High pressure liquid chromatography (HPLC), nuclear magnetic resonance spectrometry (NMR), mass spectrometry (MS). RESULTS: PTBC was isolated and identified; the concentrations in two resins were determined. HPLC analyses showed the presence of 0.099% and 0.020% wt/wt PTBC, respectively. CONCLUSION: This study shows that PTBC can be present in at least in some brands of PTBP-F-R. The study also indicates that a positive patch test reaction to PTBP-F-R could be an indication of allergy to PTBC, at least in patients with high sensitivity to PTBC. When detecting contact allergies to PTBP-F-R in a patient for whom no clinically relevant exposure to this resin can be found, the possibility of PTBC as the eliciting factor should be considered.

Antioxidants↗