Search

We demonstrate a fast electron jet along the target surface in the interaction of a femtosecond laser pulse with a solid foil. Numerical simulations show that the jet is formed due to the confinement of the surface quasistatic electromagnetic fields induced by the fast electrons themselves. The results suggest an easy way to obtain a well collimated, highly directional and stable laser-based fast electron source with a ultrashort pulse duration.

The design, synthesis, and pharmacological evaluation of a novel class of δ opioid receptor agonists, N,N-diethyl-4-(phenylpiperidin-4-ylidenemethyl)benzamide (6a) and its analogues, are described. These compounds, formally derived from SNC-80 (2) by replacing the piperazine ring with a piperidine ring containing an exocyclic carbon carbon double bond, were found to bind with high affinity and exhibit excellent selectivity for the δ opioid receptor as full agonists. 6a, the simplest structure in the class, exhibited an IC50 = 0.87 nM for the δ opioid receptors and extremely high selectivity over the μ receptors (μ/δ = 4370) and the κ receptors (κ/δ = 8590). Rat liver microsome studies on a selected number of compounds show these olefinic piperidine compounds (6) to be considerably more stable than SNC-80. This novel series of compounds appear to interact with δ opioid receptors in a similar way to SNC-80 since they demonstrate similar SAR. Two general approaches have been established for the synthesis of these compounds, based on dehydration of benzhydryl alcohols (7) and Suzuki coupling reactions of vinyl bromide (8), and are herewith reported.

Nonpeptide δ opioid agonists are analgesics with a potentially improved side-effect and abuse liability profile, compared to classical opioids. Andrews analysis of the NIH nonpeptide lead SNC-80 suggested the removal of substituents not predicted to contribute to binding. This approach led to a simplified lead, N,N-diethyl-4-[phenyl(1-piperazinyl)methyl]benzamide (1), which retained potent binding affinity and selectivity to the human δ receptor (IC50 = 11 nM, μ/δ = 740, κ/δ > 900) and potency as a full agonist (EC50 = 36 nM) but had a markedly reduced molecular weight, only one chiral center, and increased in vitro metabolic stability. From this lead, the key pharmacophore groups for δ receptor affinity and activation were more clearly defined by SAR and mutagenesis studies. Further structural modifications on the basis of 1 confirmed the importance of the N,N-diethylbenzamide group and the piperazine lower basic nitrogen for δ binding, in agreement with mutagenesis data. A number of piperazine N-alkyl substituents were tolerated. In contrast, modifications of the phenyl group led to the discovery of a series of diarylmethylpiperazines exemplified by N,N-diethyl-4-[1-piperazinyl(8-quinolinyl)methyl]benzamide (56) which had an improved in vitro binding profile (IC50 = 0.5 nM, μ/δ = 1239, EC50 = 3.6 nM) and increased in vitro metabolic stability compared to SNC-80.

When morphine and clonidine are coadministered into the spinal cord (intrathecally) the resulting antinociception is greater than would be expected if the drug responses were additive; thus, a synergistic interaction. The mechanism for this synergistic interaction was investigated using agents which alter calcium channel function and G protein function. Drugs were administered intrathecally to mice and antinociception was measured using the tail flick test. The L-type calcium channel antagonists nifedipine (15 micrograms) and verapamil (15 micrograms) and the N-type antagonist omega-conotoxin GVIA (3 and 30 ng) decreased ED50 values for both morphine and clonidine three-to five-fold. The L-type calcium channel activator Bay K 8644 had a biphasic effect; 1.7 ng increased, although 170 ng decreased, morphine and clonidine ED50 values. None of the calcium channel modifiers affected the morphine/clonidine synergism. In mice pretreated with pertussis toxin (PTX, one, 10-ng dose 21 days previously), the morphine ED50 value increased two-fold, although the clonidine ED50 value was not changed. PTX pretreatment did not alter the morphine/clonidine synergism. Also, in PTX-pretreated mice, nifedipine and 1.7 ng Bay K 8644 did not alter the morphine/clonidine synergism. However, in PTX-pretreated animals omega-conotoxin GVIA (3 ng) changed the morphine/clonidine synergism to an additive interaction. Thus, both N-type calcium channels and PTX-sensitive G proteins are likely involved in spinal morphine/clonidine synergism.

To assess the binding parameters and the structure-function relationship of the Vibrio harveyi lux autoinducer, N-(D-3-hydroxybutanoyl)homoserine lactone (D-HBHL), to light emission, a series of acylhomoserine lactone analogues were synthesized and their effects on the stimulation of luminescence of an autoinducer-deficient mutant of V. harveyi, D1, examined. Of the analogues with 3-hydroxyacyl chains, only N-(3-hydroxyvaleryl)homoserine lactone (HVHL) could act as an inducer, with about 85% of the potency of D-HBHL in stimulation of luminescence; the apparent Kd of the putative receptor for HVHL was 3.8 microM, close to that for the natural autoinducer (1.4 microM). Analogues with longer 3-hydroxyacyl chains, N-(3-hydroxyhexanoyl)homoserine lactone and N-(3-hydroxyheptanoyl)homoserine lactone, acted as competitive inhibitors of HBHL with apparent KI values of 77 and 53 microM respectively. Replacement of the 3-hydroxybutanoyl moiety with a 3-methylbutanoyl or 3-methoxybutanoyl group created weak competitive inhibitors, N-(isovaleryl)- and N-(3-methoxybutanoyl)- homoserine lactones, with apparent KI values of 150 and 360 microM respectively. Two other analogues, N-(2-hydroxybutanoyl)- and N-(4-hydroxybutanoyl)-homoserine lactone, could neither stimulate nor inhibit luminescence. The approach used in these studies to demonstrate binding of autoinducer analogues at the same site, as well as measurement of the relative dissociation constant, may be of value in analysing analogues activating or inhibiting luminescence and other processes that are under control of acylhomoserine lactone autoregulators.

The aldehydes (I) are coupled with the α‐bromo ketones (II) in the presence of metallic zinc to produce the β‐hydroxy ketones (III).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The allylalkoxysilanes (V), prepared as shown in the reaction scheme, react with the aldehydes (VIa) ‐ (VIe) to produce the 4‐chloro‐2,6‐dialkyltetrahydropyrans (VIIa) ‐ (VIIc).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The allylalkoxysilane (I) reacts with the aldehydes (II) in the presence of aluminum trichloride to yield the cis‐4‐chloro‐2,6‐disubstituted tetrahydropyrans (III).