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Comparison of the kinetic and parallel kinetic resolutions of methyl (RS)-5-tert-butyl-cyclopentene-1-carboxylate allows for the efficient synthesis of both (1R,2S,5S)- and (1S,2R,5R)-enantiomers of methyl 2-amino-5-tert-butyl-cyclopentane-1-carboxylate.
The oxygenate tert-amyl methyl ether (TAME) is a gasoline fuel additive used to reduce carbon monoxide in automobile emissions. To evaluate the relative health risk of TAME as a gasoline additive, information is needed on its pharmacokinetics and toxicity. The objective of this study was to use a physiologically-based pharmacokinetic (PBPK) model to describe the disposition of TAME and its major metabolite, tert-amyl alcohol (TAA), in male Fischer-344 rats. The model compartments for TAME and TAA were flow-limited. The TAME physiological model had 6 compartments: lung, liver, rapidly perfused tissues, slowly perfused tissues, fat, and kidney. The TAA model had 3 compartments: lung, liver, and total-body water. The 2 models were linked through metabolism of TAME to TAA in the liver. Model simulations were compared with data on blood concentrations of TAME and TAA taken from male Fischer-344 rats during and after a 6-hour inhalation exposure to 2500, 500, or 100 ppm TAME. The PBPK model predicted TAME pharmacokinetics when 2 saturable pathways for TAME oxidation were included. The TAA model, which included pathways for oxidation and glucuronide conjugation of TAA, underpredicted the experimental data collected at later times postexposure. To account for biological processes occurring during this time, three hypotheses were developed: nonspecific binding of TAA, diffusion-limited transport of TAA, and enterohepatic circulation of TAA glucuronide. These hypotheses were tested using three different model structures. Visual inspection and statistical evaluation involving maximum likelihood techniques indicated that the model incorporating nonspecific binding of TAA provided the best fit to the data. A correct model structure, based upon experimental data, statistical analyses, and biological interpretation, will allow a more accurate extrapolation to humans and, consequently, a greater understanding of human risk from exposure to TAME.
The molecules of 3-tert-butyl-5-[(4-methoxybenzyl)amino]-1-phenyl-1H-pyrazole, C21H25N3O, are linked into simple C9 chains by a single C-H...N hydrogen bond. 5-[(Benzotriazol-1-ylmethyl)(4-methoxybenzyl)amino]-3-tert-butyl-1-phenyl-1H-pyrazole, C28H30N6O, crystallizes with Z' = 2 in the space group P2(1)/c. The molecules are weakly linked into centrosymmetric tetramolecular aggregates by a combination of C-H...N and C-H...O hydrogen bonds.
In order to determine the susceptibility of newborn rats to 2-tert-butylphenol (2TBP) and 2,4-di-tert-butylphenol (DTBP) toxicity, studies were conducted with oral administration from postnatal days (PND) 4 to 21 and the findings were compared with results for young rats exposed from 5 or 6 weeks of age for 28 days. In the newborn rats, specific effects on physical and sexual development and reflex ontogeny were not observed. While there were no clear differences in toxicological profiles between newborn and young rats, the no-observed-adverse-effect levels (NOAELs) differed markedly. For 2TBP, clinical signs such as ataxic gait, decrease in locomotor activity and effects on liver, such as increase in organ weight, were observed and the NOAELs were concluded to be 20 and 100 mg/kg/day in newborn and young rats, respectively. Based on hepatic and renal toxicity (histopathological changes and increase in organ weight with blood biochemical changes), the respective NOAELs for DTBP were concluded to be 5 and 20 mg/kg/day. Therefore, the susceptibility of newborn rats to 2TBP and DTBP was found to be 4-5 times higher than that of young rats.
The search for new anti-inflammatory drugs has been constant in several research centers. The use of the Bioisostery concept allows the elaboration of new bioactive compounds with different properties through the introduction of substitute groups in one or more positions of a main molecule with known biological activity. Preliminary works accomplished at our laboratory with 2,4-thiazolidinedione isosters demonstrated inhibitory activity on edema formation for N-tryptophyl-5-(3,5-di-tert-butyl-4-hydroxybenzylidene)-2,4-thiazolidinedione (GS28) and N-tryptophyl-5-(3,5-di-tert-butyl-4-hydroxybenzylidene) rhodanine (GS26). We verified the antiedematogenic and ulcerogenic activity of these two compounds in Wistar rats. The carrageenan induced paw edema suffered significant (p<0.05) inhibition (28.36% on average) for GS28 (100 mg/kg; v.o.) during the entire time of the experiment. GS26 (50 and 100 mg/kg; v.o.) significantly inhibited (p<0.05) the paw edema dextran induced (22.1 and 27.8%, for the respective doses) after 180 min. The compounds GS26 and GS28 did not show ulcerogenic activity on gastric mucous. The results suggest antiedematogenic action for both compounds without the appearance of gastric lesions.
The effects of p-tert-butylphenyl trans-4-guanidinomethylcyclohexane carboxylate hydrochloride (NCO-650) and its metabolite, p-tert-butylphenol(BP), on the drug-metabolizing enzymes and fine structure in the rat liver were examined. Aminopyrine demethylase activity was inhibited by the administration of NCO-650 and BP at a dose of 2 and 10 mg/kg, p.o. The increases of microsomal cytochrome b5 and cytochrome P-450 contents were noticed at 1, 12 and 24 hr after NCO-650 and BP administration. Ascorbate-dependent lipid peroxidation of mitochondria and microsome increased by the administration of NCO-650 and BP, but NADPH-dependent lipid peroxidation decreased by these drugs. In the morphological observations of fine structure in the liver, NCO-650 and BP caused the swelling and decrease of rough endoplasmic reticulum and the increase of smooth endoplasmic reticulum. The morphological changes of liver fine structure were related to the changes of drug-metabolizing enzymes in the liver by the administration of NCO-650 and BP, which may be suggest the transitory and functional responses of these drugs in the liver. The effect of BP on the drug-metabolizing enzymes and fine structure in the liver was similar to that of NCO-650.
Di-tert.-butyl-dicarbonate is an ideal reagent for tert.-butyloxycarbonylating amino acids and their derivatives in regard to both reaction rate and simplicity of the procedure.
The mu opioid receptors are unquestionably implicated both in supraspinal and spinal analgesia, but there is some controversy about the role of delta receptors in the control of pain at the supraspinal level. This could be due, at least in part, to the local or i.c.v. administration of the opioid agonists. It was therefore interesting to reassess the overall contribution of mu and delta opioid receptors in modulating nociceptive thermal stimuli in the hot plate-test in mice after i.v. injections of DAMGO (Tyr-D-Ala-Gly-(NMe)Phe-Gly-ol) and BUBU (Tyr-D-Ser(O-tert-butyl)-Gly-Phe-Leu-Thr(O-tert-butyl), two highly selective mu and delta receptor agonists, respectively, whose passage into the brain has been demonstrated recently. Both agonists induced dose-dependent, short-lasting (less than 30 min), antinociceptive responses that peaked 5 min after the administration of DAMGO and 10 min after the administration of BUBU. At these times, DAMGO [ED50: 1.26 mumols (0.65 mg)/kg] was 34 times more potent than BUBU [ED50: 42.5 mumols (34 mg)/kg] in the jump response and 13 times more potent in the paw lick. Apparent pA2 values of naloxone (0.004-0.1 mg/kg s.c.) antagonism for DAMGO and BUBU did not differ significantly, 6.95 +/- 0.054 and 7.28 +/- 0.030 for paw lick tests and 7.11 +/- 0.045 and 7.25 +/- 0.027 for jump tests, respectively. The slopes of the pA2 plots were close to the theoretical -1 value for competitive antagonism.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of feeding mice and rats with 2(3)-tert-butyl-4-hydroxyanisole (BHA) and 3,5-di-tert-butyl-4-hydroxytoluene (BHT), the two most commonly used food-additive phenolic antioxidants with known anticarcinogenic properties but with only minor differences in their chemical structures, have been compared to search for common effects between the two agents in two different rodent species and then applied toward better understanding of the mechanisms involved in their protective actions. In liver microsomes of treated mice, both BHA and BHT enhanced the relative activity of aniline ring hydroxylation but decreased the relative benzo(a)pyrene monooxidase activities. However, in rats, although aniline ring hydroxylation activity was decreased by both compounds, the decrease of benzo(a)pyrene monooxidase activity was observed only with BHT. Thus, common effects could not be recognized at the microsomal mixed-function oxidase level. Contrary to expectations based on chemical structures, BHT feeding elevated by epoxide hydrolase activity to an even greater extent than that produced by BHA, especially in rats. However, enzyme activities involved in the glucuronide conjugation system (uridine diphosphate:glucuronyl transferase, uridine diphosphate:glucose dehydrogenase, and quinone reductase) are all elevated by both antioxidants in both rodent species. With BHA treatment, the levels of acid-soluble thiols were increased in both rats and mice. However, with BHT, the level was increased only in mice but not in rats. Similar trends were produced for glucose-6-phosphate dehydrogenase activity, but glutathione reductase activity was increased even for BHT-treated rats. Additionally, the glutathione S-transferase activities were also increased by both antioxidant treatments and in both rodent species. Based on these results, the elevations of epoxide hydrolase activity along with the enhanced glucuronide conjugation and glutathione oxidation and reduction conjugation system enzyme activities were common to both compounds in both rodent species. This suggests their involvement in anticarcinogenic mechanisms. Increases of these detoxification enzyme activities appeared to be all designed to accelerate the elimination of administered antioxidants but, inadvertantly, conferring protective effects from xenobiotics such as carcinogens.
We performed comparative studies to determine an acute toxicity of microsomal Ca(2+)ATPase inhibitor, 2,5-di(tert-butyl)-1,4-hydroquinone (DTBHQ) and its related analog, mono(tert-butyl)-1,4-hydroquinone (MTBHQ), which are both used as antioxodants. Wistar rats, 5 weeks old, male and female, were used. By a single dose of oral administration, DTBHQ-induced LD50 values (obtained by Lorke method) in male and female rats were estimated 295.1 and 234.4 mg/kg BW, respectively, whereas each LD50 value for MTBHQ was 711.6 and 400.0 mg/kg BW, respectively. MTBHQ-induced deaths occurred from 8 to 20 minutes after administration, however, DTBHQ-induced deaths occurred more delayed from 1 to 5 days after administration. The observed toxic signs of DTBHQ included diarrhea (jelly like), prone position, lacrimation, salivation and abnormal gait (such as reluctance to walk, limping). Localized purpura and loss of the tail (perhaps as a result of necrosis) were also observed. In comparison, MTBHQ elicited prone position, panting, staggering gait and spastic gait. Without loss of the tail montioned above, dead and sacrified rats showed no remarkable changes in macroscopic examination due to exposure to both compounds.
Topaquinone (TPQ) is a cofactor present at the active site of copper amine oxidases, derived from a Tyr residue inserted in the polypeptide chain through a copper-dependent but otherwise largely unknown mechanism. A simple model system was developed that permits to obtain the overall transformation of 4-tert-butylphenol, chosen as a model for Tyr, into a TPQ-like, para-hydroxyquinonic structure in the presence of Cu(II)-imidazole mononuclear complexes.
The reaction between beta-diketiminato-stabilized aluminum dihydride LAlH2 and tBuOOH leads to the formation of a pentacoordinated tert-butylperoxo aluminum compound.
The compound 2,6-bis(N-tert-butylacetamide)pyridine (2) was obtained via a Ritter synthesis, and oxidation with oxone provided the title pyridine-N-oxide (3). The compounds were characterized by spectroscopic methods, and the molecular structure of the N-oxide was determined by single-crystal X-ray diffraction methods. The coordination chemistry with Eu(NO3)3 was examined by using 1:1 and 2:1 ligand/Eu ratios, and a single-crystal X-ray analysis for Eu(3)(NO3)3(H2O) was completed. The ligand 3 is found to chelate in a tridentate fashion on the Eu(III).
Oxidation-reduction condensation using in situ-formed alkoxydiphenylphosphines, 2,6-dimethyl-1,4-benzoquinone, and carboxylic acids provided a new and efficient method for the preparation of inverted tert-alkyl carboxylates from various chiral tertiary alcohols.
tert-Butyl radicals add to the carbon atom of benzylideneanilines to form anilino radicals, which are protonated in the presence of PTSA or NH(4)(+) in Me(2)SO. Reduction of the resulting aniline radical cations occurs readily by the ate complex, t-BuHgI(2)(-). In the absence of a proton donor, t-BuHgI will also transfer a hydrogen atom to the anilino radical to give the reductive alkylation product. Protonation can promote a free radical chain process involving electron transfer by substrate activation and/or by increasing the electron affinity of the intermediate radicals. Since the adduct radicals formed from benzylideneanilines are more easily protonated than the parent Schiff bases, PTSA but not NH(4)(+) demonstrates substrate activation, although both proton donors promote the free radical reaction.
The chiral ligand controlled asymmetric conjugate addition reaction of lithium N-allyl-N-(tert-butyldimethylsilyl)amide to alkenoates proceeded smoothly to give, after protodesilylation, the corresponding 3-allylaminoalkanoates with high enantioselectivities in high yields. The allyl group on the nitrogen atom was easily removable to afford 3-aminoalkanoates.
Application of N alpha,Nca-di-tert-butyloxycarbonylhomoglutamine to synthesis of thyrotropin-releasing hormone (TRH) analogs was examined. The delta-lactam formation from homoglutaminylpeptides took place more easily than gamma-lactam formation from glutaminylpeptides in water or dioxane containing acetic acid. [pHgu1,Nva2]-TRH had dose-dependent antagonistic activity against pentobarbital anesthesia in mice, but almost no binding activity to TRH receptor in rat brain.
Ethene/norbornene copolymerization by the catalyst system [Me2Si(3-(tert)BuCp) (N(tertBu)]TiCl2/ MAO was investigated in detail at 30 degrees C, 60 degrees C, and 90 degrees C. A mass flow controller was used in this work to obtain kinetic data and investigate temperature's effects on activity, norbornene incorporation, copolymerization parameter, microstructure, glass transition temperature, and molar masses were described. High copolymerization values r(E) and high alternation are determined. The number of isotactic alternating sequences is much higher than that of the syndiotactic alternating sequences.