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Planar-chiral (2E,7Z)- and (2Z,7E)-cyclonona-2,7-dien-1-yl carbamates by asymmetric, bis-allyic, alpha, alpha'-cycloalkylation--studies on their conformational stability.

Enantiomerically enriched (>80 % ee) (M,1R,2Z,7E)- and (M,1R,2E,7Z)-cyclonona-2,7-dienyl carbamates have been synthesized by an intramolecular cycloalkylation of the corresponding 1-lithio-9-chloronona-2,7-dienyl carbamates. The enantioenriched precursors were generated by asymmetric deprotonation of the dienyl carbamates by means of n-BuLi/(-)-sparteine. The primarily obtained cyclononadienes, each bearing one element of planar and centre chirality, were formed by an , coupling of both allylic moieties. These are the thermodynamically less favoured epimers, which arise from those allyllithiums bearing the carbamoyloxy residue in a 1-endo position. Both (M,R)-cyclononadienes epimerize slowly (t(1/2) = 209 min and 328 min at 308 K) with inversion of the planar chirality to the corresponding, more stable (P)-epimers (ratios 3:97 and 30:70). The kinetics were measured by 1H NMR spectroscopy, the activation energies EA were found to be 26.4 and 27.5 kcal mol(-1). From quantum-chemical calculations with the B3LYP density functional, the epimerization process was shown to consist of two coupled major conformational changes with high energy barriers. The calculated values match well with the observed ones.

Journal Article↗

Intralitter variation in murine fetal sister chromatid exchange responses to the transplacental carcinogen ethyl carbamate.

Gravid Swiss Webster dams were injected via tail vein with a single (1.1, 2.2, or 3.3 mmol/kg) dose of ethyl carbamate (urethane) on days 13-17 of pregnancy. Relative sister chromatid exchange (SCE) responses in maternal bone marrow vs. individual fetal liver cells were assessed. In addition, in order to evaluate the significance of intralitter variability in fetal SCE responses, SCE in combined ("pooled") fetal liver tissue preparations were measured and compared with average individual responses. In contrast to maternal responses, average fetal SCE responses to ethyl carbamate varied with gestational age. In addition, significant variation was observed among individual littermate responses at all dose levels. Nonetheless, fetal SCE responses determined from "pooled" tissue preparations provided a valid estimate of average litter responses. Regardless of the method of SCE evaluation in fetal tissue or gestational age, maternal bone marrow exhibited greater sensitivity than fetal liver to SCE induction by ethyl carbamate.

Age Factors↗

Estimating a worker entry interval for the carbamate pesticide furadan 4F insecticide.

Existing methods for the calculation of worker entry intervals by the use of kinetic data have focused on the anticholinesteratic organic phosphates. As carbamate pesticides share with these materials a common site for inhibition, the kinetic method was applied in estimating an entry interval for the carbamate, carbofuran, applied to citrus and grapes as Furadan 4F. No allowance was made for the more transient carbamylation of cholinesterase attributed to N-methyl carbamates, compared with the phosphorylation of the enzyme by organic phosphates. Thus, a measure of safety was built into the calculations which can then be used to establish safe reentry intervals to insure residue levels below the physiological threshold for cholinesterase inhibition.

Agricultural Workers' Diseases↗

Acute pancreatitis after carbamate insecticide intoxication.

A 29-year-old woman was admitted to the Rouen University Hospital for attempted suicide by ingestion of a carbamate insecticide (Temik G, containing 10% aldicarb). Cardio-respiratory arrest occurred at the second hour and acute necrotic hemorrhagic pancreatitis on the second day. Further evolution was uneventful, and the patient was discharged after 43 days. Carbamate intoxication was confirmed by high urinary aldicarb metabolite concentrations. Pseudocholinesterase levels took 77 days to return to normal. Carbamate pesticides share the same pancreatic risk as organophosphorus pesticides, and should be monitored similarly.

Acute Disease↗

Experimental and theoretical studies of anthelmintics: oxfendazole and its imidazo[1,2-a]pyridine-2-carbamate isomer.

Mice experimentally infected with Trichinella spiralis were used to test the therapeutic effectiveness of an anthelmintic, methyl 6-(phenylsulfinyl)imidazo[1,2-a]pyridine-2-carbamate, against the immature and adult worms during the intestinal phase of infection. A single oral dose of 100 mg kg-1 of the drug on the third day after exposure to infection was totally ineffective against the adult worms as determined at necropsy on day 6. Neither higher unit dosages of the drug, division of the daily oral dose, nor increasing the length of the treatment period from 1 to 4 days enhanced drug activity in vivo. Furthermore the drug was inactive as a single oral dose against the immature worms at all of the dosages tested (12.5-400 mg kg-1). These results are in marked contrast to those obtained previously with oxfendazole (methyl 5[6]-(phenylsulfinyl)benzimidazole-2-carbamate) under comparable experimental conditions and clearly indicate that the two compounds are not anthelmintically equivalent in the T. spiralis-infected mouse system in spite of their similar structural features. A quantum mechanical study of these drugs was undertaken and a hypothesis for the inactivity of the imidazo[1,2-a]pyridine-2-carbamate isomer is proposed.

Animals↗

Carbamates, atropine, and diazepam: effects on performance in the running rat.

We have reported that when rats (500 g, male) are exercised to exhaustion on a treadmill, pretreatment with the centrally acting carbamate physostigmine reduced endurance (run time, RT) and increased the rate of rise of core temperature (Tc+). Both RT and Tc+ were restored to control levels by pretreatment with either or a combination of atropine (A), and diazepam (D). Our objective in the present work was to determine whether A+D could also restore the performance and thermoregulatory decrements induced by the peripherally acting carbamate pyridostigmine (PY). After drug administration, rats were run (11 m/min, 6 degrees elevation, Ta = 26 degrees C) to exhaustion. PY treatment resulted in a reduced RT and an increased heat gain that neither A nor D alone (A+PY and D+PY) could restore to control levels. On the other hand, a combination of both A and D restored these variables to control levels. In conclusion, A+D can restore the performance and thermoregulatory decrements resulting from the administration of either a centrally or a peripherally acting carbamate.

Animals↗

1-naphthyl N-methyl carbamate effect on intra- and extracellular concentrations of arachidonic acid metabolites, and on the chemiluminescence generation by mouse peritoneal macrophages.

1-Naphthyl N-methyl carbamate (carbaryl), potent carbamate insecticide with anticholinesterase activity, was tested for its ability to affect mouse peritoneal macrophages in particular arachidonic acid (AA) metabolism and oxidative burst. Carbaryl inhibited in a dose-related manner the reactive oxygen intermediate dependent chemiluminescence (CL) induced by opsonized zymosan (OZ), 12-O-tetradecanoyl phorbol-13-acetate (TPA) and calcium ionophore (A23187); this carbamate did not affect CL-mediated by AA. The intracellular and extracellular concentrations of prostaglandins (PGs) and 5-hydroxyeicosatetraenoic (5-HETE) generated in macrophages stimulated with OZ has been investigated for various periods. Carbaryl effect displayed two successive phases on AA metabolism stimulation. In a first phase (up to 2-15 min), carbaryl did not alter the rapid AA metabolite synthesis (total amount of intra- and extracellular metabolites) but it increased intracellular concentration of PGE2, PGA2, PGF2 alpha and decreased 5-HETE intracellular concentration. In a second phase (after 2-15 min), carbaryl inhibited AA metabolite synthesis. The release of cyclooxygenase (CO) and lipoxygenase (LO) metabolites decreased, in particular PGF2 alpha and PGD2 which in addition seemed to be submit to a cellular retention; the inhibition of other metabolite release appeared essentially related to the inhibition of their synthesis since the intracellular amount did not augment. The inhibition by carbaryl of the NADPH-oxidase dependent CL induced by OZ may be related to the alteration of the intra- and extracellular concentrations of AA metabolites.

Animals↗

Oxime effects on the rate constants of carbamylation and decarbamylation of acetylcholinesterase for pyridostigmine, physostigmine and insecticidal carbamates.

The effects of the oximes 2-pyridine aldoxime methiodide (PAM), HI-6, HS-6, toxogonin and TMB-4 on the rate of carbamylation of membrane-bound bovine erythrocyte acetylcholinesterase were studied. The second-order rate constant of carbamylation (ki) and the first-order rate constant of decarbamylation (k3) were calculated from the proportion of free acetylcholinesterase at equilibrium and the rate of approach to equilibrium. Twenty insecticidal carbamates plus physostigmine and pyridostigmine were studied. The oximes increased ki for several carbamates, with HI-6 causing an increase in the most number of cases (12) and PAM the least (3). HI-6 was also a potent accelerator of decarbamylation (increase in k3) in all cases, whereas PAM caused a significant decrease in k3 in 15 cases and a nonsignificant decrease in the other 7. Toxogonin and TMB-4 increased k3 or had no significant effect. The results were generally consistent with a proposal in the literature that there is a correlation between increased ki and increased toxicity of the carbamate in the presence of an oxime.

Acetylcholinesterase↗

Effect of ethanol on the induction of lung tumours by ethyl carbamate in mice.

Groups of 25 female NMRI-mice received daily doses of 0, 18, 36, 90, or 180 mg ethyl carbamate/kg body wt either in water or in 20% ethanol by gavage for 8 weeks. Another 8 weeks later, the animals were sacrificed and lung adenomas were counted. Ethyl carbamate was found to increase the number of lung adenomas per mouse dose-dependently in all dose groups. No significant differences, however, were observed between groups receiving ethyl carbamate in water or in 20% ethanol. Thus, ethanol had no effect on ethyl carbamate induced tumourigenesis.

Adenoma↗

New C25 carbamate rifamycin derivatives are resistant to inactivation by ADP-ribosyl transferases.

A novel series of 3-morpholino rifamycins in which the C25 acetate group was replaced by a carbamate group were prepared and found to exhibit significantly improved antimicrobial activity than rifampin against Mycobacterium smegmatis. Further characterization of such compounds suggests that relatively large groups attached to the rifamycin core via a C25 carbamate linkage prevent inactivation via ribosylation of the C23 alcohol as catalyzed by the endogenous rifampin ADP-ribosyl transferase of M. smegmatis. SAR studies of the C25 carbamate rifamycin series against M. smegmatis and other bacteria are reported.

ADP Ribose Transferases↗

Anti-apoptotic action of anti-Alzheimer drug, TV3326 [(N-propargyl)-(3R)-aminoindan-5-yl]-ethyl methyl carbamate, a novel cholinesterase-monoamine oxidase inhibitor.

The anti Parkinson drug, rasagiline [R-(+)-N-propargyl-1-aminoindan], an inhibitor of type B monoamine oxidase, has been shown to suppress apoptosis induced by neurotoxins and oxidative stress. A series of novel propargylaminoindans with a carbamate moiety to inhibit cholinesterase were developed from phamacophore of rasagiline to protect or rescue deteriorated neurons in Alzheimer's and Lewy Body disease and provide a beneficial effect on the cognitive deficits. Rasagiline analogues were found to protect dopaminergic SH-SY5Y cells against apoptosis induced by peroxynitrite donor. SIN-1. TV3326, [(N-propargyl)-(3R)-aminoindan-5-yl]-ethyl methyl carbamate, was as effective as rasagiline in preventing apoptosis, followed by its S-enantiomer, TV3279. The anti-apoptotic-neuroprotective activity was shown to reside in the propargylamine and not the carbamate moiety. This resulted in stabilization of the mitochondrial membrane potential, the collapse of which initiates the apoptotic cascade.

Alzheimer Disease↗

Possible mechanisms for sensitivity to organophosphorus and carbamate insecticides in eastern screech-owls and American kestrels.

Effects of a single dietary exposure to fenthion and carbofuran on the survival, feeding behavior and brain ChE activity of eastern screech-owls, Otus asio and American kestrels, Falco sparverius, were evaluated. Birds were exposed to fenthion (23.6-189.0 ppm) or carbofuran (31.7-253.6 ppm) via meatballs. Carbofuran-exposed owls ate either < or = 10% or > or = 80% of the meatball whereas all kestrels ate < or = 10% of the meatball before exhibiting acute signs of toxicity. Fenthion-exposed owls and kestrels displayed a wide spectrum of meatball consumption (< 10-100%). Significant brain ChE inhibition was observed in dead and surviving kestrels exposed to fenthion and carbofuran and dead owls exposed to fenthion (P < 0.0001). Brain ChE activity of owls exposed to carbofuran that survived was not different from that of controls (P = 0.25). Data suggest: (1) slow feeding on a carbamate-contaminated item may provide limited protection from the toxicity of the chemical at certain rates of exposure; (2) the degree of ChE inhibition at neuromuscular junctions may be critical in determining the sensitivity of a species to a carbamate insecticide; (3) sensitivity may be a function of the ChE affinity for the carbamate inhibitor; and (4) the importance of neuromuscular junction ChE depression in determining the sensitivity of an animal may be species-specific.

Animals↗

Cyanomethyl anion/carbon dioxide system: an electrogenerated carboxylating reagent. Synthesis of carbamates under mild and safe conditions.

A new carboxylating reagent ((-)CH(2)CN/CO(2)) was obtained by bubbling CO(2) in a CH(3)CN-TEAP (tetraethylammonium perchlorate) solution previously electrolyzed under galvanostatic control. Organic carbamates were isolated from these solutions after addition of amines and an alkylating agent. In this paper, we describe the optimized conditions for the electrochemical synthesis of carbamates from amines and CO(2), in mild and safe conditions, without any addition of bases, probases, or catalysts. Carbamates were isolated from primary and secondary aliphatic amines in high to excellent yields and from aromatic amines in moderate yields (dependent on the nucleophilicity of the nitrogen atom).

Journal Article↗

Solution-phase parallel synthesis of carbamates using polymer-bound N-hydroxysuccinimide.

[formula: see text] A convenient method for the synthesis of carbamates using polymer-supported N-hydroxysuccinimide is described. Various carbamates were synthesized in highly pure form without the need for chromatographic purification. This new "catch and release"-type solid-phase synthesis should be useful for combinatorial synthesis of various carbamates.

Journal Article↗

Molecular basis of neuroprotective activities of rasagiline and the anti-Alzheimer drug TV3326 [(N-propargyl-(3R)aminoindan-5-YL)-ethyl methyl carbamate].

Rasagiline (N-propargyl-1-(R)-aminoindan) is a selective, irreversible monoamine oxidase B (MAO B) inhibitor which has been developed as an anti-Parkinson drug. In controlled monotherapy and as adjunct to L-dopa it has shown anti-Parkinson activity. In cell culture (PC-12 and neuroblastoma SH-SY5Y cells) it exhibits neuroprotective and anti-apoptotic activity against several neurotoxins (SIN-1, MPTP, 6-hydroxydopamine and N-methyl-(R)-salsolinol) and ischemia. In vivo, it reduces the sequelae of traumatic brain injury in mice and speeds their recovery. The neuroprotective activity of rasagaline does not result from MAO B inhibition, since its S-enantiomer, TVP1022, which has 1000-fold weaker MAO inhibitory activity, exhibits similar neuroprotective properties. Introduction of a carbamate moiety into the rasagiline molecule to confer cholinesterase inhibitory activity for the treatment of Alzheimer's disease, resulted in compounds TV3326 [(N-Propargyl-(3R)Aminoindan-5-YL)-Ethyl Methyl Carbamate] and its S-enantiomer TV3279 [(N-Propargyl-(3S)Aminoindan-5-YL)-Ethyl Methyl Carbamate], which retain the neuroprotective activities of rasagiline and TVP1022. They also antagonize scopolamine-induced impairments in spatial memory. In addition, TV3326 exhibits brain-selective MAO A and B inhibitory activity after chronic administration and has antidepressant-like activity in the forced swim test. This is associated with an increase in brain levels of serotonin. The anti-apoptotic activity of these propargylamine-containing derivatives may be related to their ability to delay the opening of voltage-dependent anion channels (VDAC), which are part of the mitochondrial permeability transition pore. The propargylamine moiety is responsible for the increase in the mitochondrial family of Bcl-2 proteins, prevention in the fall in mitochondrial membrane potential, prevention of the activation of caspase 3, and of translocation of glyceraldehyde-3-phosphate dehydrogenase from the cytoplasm to the nucleus. The latter processes are closely associated with neurotoxin-induced apoptosis. Rasagiline interacts with and prevents the binding of PKI 1195 to the pro-apoptotic peripheral benzodiazepine receptor, which together with Bcl-2, hexokinase, porin, and adenine nucleotide translocator constitutes part of the VDAC. Furthermore, rasagiline, TV3326 and TV3279 are able to influence the processing of amyloid precursor protein by activation of alpha-secretase and increasing the release of soluble alpha APP in rat PC-12 and human neuroblastoma SH-SY5Y cells and in rat and mice cortex and hippocampus. This process has been shown to involve the upregulation of PKC and MAP kinase. It is quite likely that the induction of Bcl-2 and activation of PKC by rasagiline and TV3326 is closely linked to the anti-apoptotic action of these drugs and their ability to process APP by activation of alpha-secretase.

Alzheimer Disease↗

Carbamate kinase from Enterococcus faecalis and Enterococcus faecium--cloning of the genes, studies on the enzyme expressed in Escherichia coli, and sequence similarity with N-acetyl-L-glutamate kinase.

Carbamate kinase (CK) catalyzes the reversible reaction NH2COO- + ATP <--> NHCOOPO3(2-) + ADP, serving to synthesize ATP from carbamoyl phosphate in those microorganisms that derive energy from anaerobic arginine degradation via the arginine dihydrolase pathway. We report here the cloning and sequencing of the CK gene from Enterococcus faecalis and Enterococcus faecium and we demonstrate that the amino acid sequence of CK is identical in the two species. The enzyme, expressed and isolated from Escherichia coli using simple purification procedures, was used to generate crystals suitable for X-ray studies and to investigate the utilization by CK of bicarbonate and other carbamate analogs. CK had a bicarbonate-dependent ATPase activity and, therefore, is able to synthesize carboxyphosphate, an unstable compound that is an intermediate in the reactions catalyzed by carbamoyl-phosphate synthetase (CPS) and by biotin carboxylase. Other functional similarities with CPS include the utilization of acetate by CK with a similarly high Km and the similar Km values of CK for carbamate and of CPS for bicarbonate. Enterococcal CK was inhibited by adenosine(5')pentaphospho(5')adenosine (Ap5A) and Ap6A and, less powerfully, by Ap4A, whereas Ap3A is essentially non-inhibitory. Thus, inhibition by Ap5A seems not to be a valid criterion to differentiate between CK and CPS, for the two enzymes can be inhibited by Ap5A. All these results support the relatedness of CK and CPS. Finally, we used limited proteolysis: (a) to localize the epitopes for monoclonal antibodies obtained against CK; (b) to demonstrate the importance of the C-terminus for enzyme activity; and (c) to show that Arg158 is highly exposed and may be essential for activity. Comparison of the sequence of CK with known protein sequences demonstrates considerable similarity of CK with bacterial N-acetylglutamate kinases, strongly suggesting that these two enzymes may share a similar structure and the same catalytic mechanism.

Amino Acid Sequence↗

Detection of 1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine by immunoaffinity/32P-postlabelling in liver and lung DNA of mice treated with ethyl carbamate (urethane) or its metabolites.

The capacity of the chemical carcinogen ethyl carbamate (EC, urethane) and its metabolites vinyl carbamate (VC) and vinyl carbamate epoxide (VCO) to form ethenobases was studied in liver and lung DNA of 12-day-old and adult CD-1, B6C3F1, C3H/HeJ and C57BL/6J mice. Following single and multiple doses of EC, VC or VCO, the formation of 1,N6-ethenodeoxyadenosine (epsilon dA) and 3,N4-ethenodeoxycytidine (epsilon dC) was quantified by an immunoaffinity chromatography/32P-postlabelling technique. Both etheno adducts were detected in untreated control DNA samples from liver and lung in the range of 2-15 adducts/10(9) parent nucleotides. Following five repeated injections of 250 or 280 nmol/g body wt VC to adult mice, 51, 57 and 78 epsilon dA/10(9) dA and 28, 42 and 42 epsilon dC/10(9) dC (means of duplicate analyses) were detected in liver DNA of CD-1, C3H/HeJ and C57BL/6J mice respectively. In lung DNA of these VC-treated mice, the levels were 87, 49 and 58 (epsilon dA/10(9) dA) and 64, 39 and 43 (epsilon dC/10(9) dC) respectively. Under similar dose regimens, lower levels of etheno adducts were detected in B6C3F1 mice. Etheno-DNA adducts were also formed in liver and lung upon treatment with EC in adult mice, but at 3-fold lower levels as compared with VC. In 12-day-old C3H/HeJ and C57BL/6J mice, 2- to 3-fold higher etheno adduct levels were detected in liver DNA, when compared with adults, upon a single treatment with 250 nmol/g body wt VC, suggesting that young animals are more susceptible to adduct formation. Combined analysis of adduct formation in adult CD-1, C3H/HeJ and C57BL/6J mice at the higher dose showed a statistically significant increase in etheno adduct formation in the order EC > VC. The results demonstrate that EC and its activated intermediates bind to liver and lung DNA to form epsilon dA and epsilon dC, and the differences in DNA binding further support the hypothesis that metabolic activation of EC to VC is involved. Preliminary data also suggest that background levels of epsilon dA and epsilon dC in DNA are affected by the type of diet given to the animals.

Animals↗

Plant epicuticular lipids: alteration by herbicidal carbamates.

The effect of several carbamates and trichloroacetic acid on the biosynthesis of epicuticular lipids from leaves of pea (Pisum sativum) was tested by chemical and visual methods. The carbamates tested included S-(2,3-dichloroallyl) diisopropylthiocarbamate (diallate), N-(3-chlorophenyl) isopropylcarbamate (chloropropham), S-ethyl dipropylthiocarbamate, and 2-chloroallyl diethyldithiocarbamate. Diallate reduced epicuticular lipids by 50% when the plants were root-treated and by 80% when vapor-treated. These results were supported by scanning electron microscopy and carbon replica techniques with transmission electron microscopy. The ratio of wax lipid components in the diallate-treated plants remained unchanged, with the exception of the primary alcohols, which were reduced. Diallate appears to interfere with the biosynthesis of a precursor to the elongation-decarboxylation pathway of lipid synthesis. N-(3-Chlorophenyl)isopropylcarbamate had no significant effect on total amounts of extractable epicuticular lipids, nor did it alter the structure of the wax formation on the leaves. The scanning electron microscopy micrographs indicated that S-ethyl dipropylthiocarbamate significantly reduced wax formation on pea leaves. 2-Chloroallyl diethyldithiocarbamate altered the structure of the wax formations, but not the total amount of wax (scanning electron microscopy). Trichloroacetic acid had little effect on wax deposition compared to diallate or S-ethyl dipropylthiocarbamate (scanning electron microscopy). The implication of the effect of the carbamates on epicuticular lipids and penetration of subsequent topically applied chemicals is discussed.

Journal Article↗