Regioselective synthesis of N-beta-hydroxyethylaziridines by the ring-opening reaction of epoxides with aziridine generated in situ.
(65/274)[reaction: see text] Biologically important N-beta-hydroxyethylaziridine intermediates were conveniently prepared by regioselective ring-opening reactions of diversely substituted epoxides. Ethyleneimine generated in situ under basic conditions from beta-chloroethylamine was used as a nucleophile to open the epoxides in an aqueous environment. (+info)
Inactivation of infectious bursal disease virus by binary ethylenimine and formalin.
(66/274)In this experiment conducted to study the inactivation dynamics of infectious bursal disease virus (IBDV) by binary ethylenimine (BEI) in comparison with formalin, IBDV was isolated from the bursa of infected chickens and its confirmation was done by agar gel precipitation test. Viral suspensions were subjected to inactivation with BEI and formalin for pre-set time intervals. BEI was employed at concentrations of 0.001 and 0.002 mol/L while formalin was used at 0.1% and 0.2%. Sampling was done at 6, 12, 24, 36 and 48 h of incubation and samples were tested for their inactivation status in 9-day-old embryonated eggs and 3-week-old broiler chickens. IBDV was completely inactivated by 0.001 and 0.002 mol/L BEI after 36 h of incubation at 37 degrees C, whereas formalin at 0.1% and 0.2% concentrations inactivated IBDV in 24 h. (+info)
Structural insights into stereochemical inversion by diaminopimelate epimerase: an antibacterial drug target.
(67/274)D-amino acids are much less common than their L-isomers but are widely distributed in most organisms. Many D-amino acids, including those necessary for bacterial cell wall formation, are synthesized from the corresponding L-isomers by alpha-amino acid racemases. The important class of pyridoxal phosphate-independent racemases function by an unusual mechanism whose details have been poorly understood. It has been proposed that the stereoinversion involves two active-site cysteine residues acting in concert as a base (thiolate) and an acid (thiol). Although crystallographic structures of several such enzymes are available, with the exception of the recent structures of glutamate racemase from Bacillus subtilis and of proline racemase from Trypanosoma cruzi, the structures either are of inactive forms (e.g., disulfide) or do not allow unambiguous modeling of the substrates in the active sites. Here, we present the crystal structures of diaminopimelate (DAP) epimerase from Haemophilus influenzae with two different isomers of the irreversible inhibitor and substrate mimic aziridino-DAP at 1.35- and 1.70-A resolution. These structures permit a detailed description of this pyridoxal 5'-phosphate-independent amino acid racemase active site and delineate the electrostatic interactions that control the exquisite substrate selectivity of DAP epimerase. Moreover, the active site shows how deprotonation of the substrates' nonacidic hydrogen at the alpha-carbon (pKa approximately 29) by a seemingly weakly basic cysteine residue (pKa approximately 8-10) is facilitated by interactions with two buried alpha-helices. Bacterial racemases, including glutamate racemase and DAP epimerase, are potential targets for the development of new agents effective against organisms resistant to conventional antibiotics. (+info)
Aziridine-2,3-dicarboxylates, peptidomimetic cysteine protease inhibitors with antileishmanial activity.
(68/274)Chemotherapy of leishmaniasis is mainly based on antimonials. However, they are extremely toxic and cause serious side effects, and there is a worldwide increasing frequency of chemoresistance to antimonials. These issues emphasize the urgent need for affordable alternative drugs against leishmaniasis. Leishmania cysteine proteases are essential for parasite growth, differentiation, pathogenicity, and virulence and are thus attractive targets for combating leishmaniasis. Herein we demonstrate that the cysteine protease inhibitors aziridine-2,3-dicarboxylates 13b and 13e impaired promastigote growth at mid-micromolar concentrations and decreased the infection rate of peritoneal macrophages at concentrations 8- to 13-fold lower than those needed to inhibit parasite replication. Simultaneous treatment of infected cells with compound 13b and gamma interferon resulted in an even further reduction of the concentration needed for a significant decrease in macrophage infection rate. Notably, treatment with the compounds alone modulated the cytokine secretion of infected macrophages, with increased levels of interleukin-12 and tumor necrosis factor alpha. Furthermore, the decreased infection rate in the presence of compound 13b correlated with increased nitric oxide production by macrophages. Importantly, at the concentrations used herein, compounds 13b and 13e were not toxic against fibroblasts, macrophages, or dendritic cells. Together, these results suggest that the aziridine-2,3-dicarboxylates 13b and 13e are potential antileishmanial lead compounds with low toxicity against host cells and selective antiparasitic effects. (+info)
Immunogenicity of formaldehyde and binary ethylenimine inactivated infectious bursal disease virus in broiler chicks.
(69/274)Infectious bursal disease virus (IBDV) was inactivated by two different chemicals--formaldehyde and binary ethylenimine (BEI). Formaldehyde was used at 0.1% and 0.2%, while BEI was used at concentrations of 0.001 and 0.002 mol/L. These four vaccines were tested for their efficiency in generating humoral immune response in different groups of broiler chicks. Both BEI-inactivated vaccines gave relatively higher antibody titers and were almost twice as efficient as formaldehyde-inactivated ones. (+info)
Synthesis of substituted phenyl diaziridines and characterization as mechanism-based inactivators of human cytochrome P450 2B6.
(70/274)The metabolism of arylhydrazines by cytochromes P450 (P450s) has previously been shown to yield aryl-iron complexes that inhibit P450 enzymes as a result of heme modification. These modifications of the heme have been used to probe the topology of the active site of several P450s. Therefore, diaziridines containing one or more substitutions on the phenyl ring were synthesized and evaluated as potential mechanism-based inactivators of P450 2B enzymes that could be used to elucidate the active site topology. Five of the six trifluoroaryldiaziridines tested selectively inactivated P450 2B6 in the reconstituted system in a time-, concentration-, and NADPH-dependent manner as measured using the 7-ethoxy-4-(trifluoromethyl)coumarin O-deethylation assay. The kinetic parameters for P450 2B6 inactivation by the five compounds were calculated. Analysis of the P450 heme from P450s inactivated by the five substituted diaziridines suggested that the activity loss was not due to heme destruction as measured by the reduced-CO spectrum or high-performance liquid chromatography of the P450 heme. Dialysis experiments indicated the irreversible nature of the inactivation and the reaction between the diaziridine compounds and the P450 enzyme. Interestingly, a thiomethyl-substituted phenyl diaziridine had no effect on the activity of P450 2B6 in the reconstituted system, but competitively inhibited the O-debenzylation activity of P450 3A4 with 7-benzyloxy-4-(trifluoromethyl)coumarin as substrate. Binding spectra suggest that this compound bound reversibly to P450 2B6, and preliminary results indicate that 3-(4-methylthiophenyl)-3-(trifluoromethyl)diaziridine is metabolized by P450 2B6. (+info)
Strain-release rearrangement of N-vinyl-2-arylaziridines. Total synthesis of the anti-leukemia alkaloid (-)-deoxyharringtonine.
(71/274)Deoxyharringtonine (1) is among the most potent of the anti-leukemia alkaloids isolated from the Cephalotaxus genus. A convergent total synthesis of (-)-1 is reported, involving novel synthetic methods and strategies that include (1) the strain-release rearrangement of N-aryl-2-vinylaziridines for benzazepine synthesis, (2) a vinylogous amide acylation-cycloaddition cascade for spiro-pyrrolidine construction, and (3) efficient acylation of the cephalotaxine core by alpha-(beta-lactone)carboxylic acid derivatives to access the biologically active cephalotaxus esters. These innovations should allow rapid access not only to other Cephalotaxus alkaloids but also to non-natural analogues of potential therapeutic utility. (+info)
Generation of aza-ortho-xylylenes via ring opening of 2-(2-acylaminophenyl)aziridines: application in the construction of the communesin ring system.
(72/274)A new protocol for generating aza-ortho-xylylenes via acid-catalyzed or fluoride-promoted ring opening of 2-(2-acylaminophenyl)aziridines is described. This methodology has been exploited in the rapid construction of a hexacyclic substructure of communesin B. (+info)