New Mixed Li/Mg and Li/Mg/Zn Amides for the Chemoselective Metallation of Arenes and Heteroarenes

New mixed Li/Mg and Li/Mg/Zn amides have been synthesized starting from readily prepared secondary amines. They allow a highly chemoselective directed magnesiation or zincation of various polyfunctional aromatics and heteroaromatics. The kinetic basicity, solubility and stability of these new bases have been compared with those of the corresponding 2,2,6,6-tetramethylpiperamide-derived bases. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Isobutyl amides - potent compounds for controlling Diatraea saccharalis

BACKGROUND: A dichloromethane-methanol extract of the seeds of Piper tuberculatum Jacq. (Piperaceae) and two isobutyl amides, 4,5-dihydropiperlonguminine (1) and pellitorine (2), which were isolated by chromatographic methods, were assayed for their lethality against the sugarcane borer Diatraea saccharalis F. (Lepidoptera: Pyralidae). RESULTS: Bioassays were carried out with fourth-instar caterpillars through topical application of test solutions to the dorsal surface of the prothorax, and dose-response correlations were determined. Significant insect mortalities were observed 24, 48 and 72 h after treatment at concentrations of >= 100 mu g insect(-1). The LD(50) and LD(90) values for compound 1 were 92.83 and 176.50 mu g insect(-1), and for compound 2 they were 91.19 and 184.56 mu g insect(-1). CONCLUSION: According to the LD(50) and LD(90) for compounds 1 and 2, it can be inferred that the values reflect an acute lethal response to both compounds, based on interaction(s) of the toxicants with a primary target or series of targets. Thus, the amides were demonstrated to have potential value in the control of the sugarcane borer. (C) 2008 Society of Chemical Industry

Chemoenzymatic synthesis of boron-containing chiral amines and amides

The first application of lipases as catalysts to obtain optically active boron-containing amines and amides is described. We studied several reaction conditions to achieve the kinetic resolution of boron-containing amines via enantioselective acylation mediated by Candida antarctica lipase B (CAL-B). Excellent enantioselectivity (E>200) and high enantiomeric excess (up to >99%) of both the remaining amines and amides were obtained. (C) 2010 Elsevier Ltd. All rights reserved.

First chemoenzymatic synthesis of organoselenium amines and amides

A series of organoselenium amines have been synthesized and submitted to the enzymatic kinetic resolution by acetylation mediated by CAL-B (Novozym 435) to give the corresponding chiral amides in an enantiomerically pure form. After evaluating the appropriate lipase, solvent, temperature,and lipase/substrate ratio in the kinetic resolution, the chiral organoselenium amides were obtained with enantiomeric excess of up to 99%. (C) 2008 Elsevier Ltd. All rights reserved.

Mild and efficient one-pot synthesis of chiral beta-chalcogen amides via 2-oxazoline ring-opening reaction mediated by indium metal

A simple and efficient procedure for the synthesis of beta-seleno and beta-thio amides via the ring-opening reaction of chiral 2-oxazolines in the presence of indium metal has been developed. Features of this method include the following: (i) easily and accessible starting materials; (ii) indium metal is more stable and less expensive then its respective salts; (iii) useful to excellent yields of beta-chalcogen amides derivatives. (C) 2008 Elsevier B. V. All rights reserved.

Insect feeding preferences on Piperaceae species observed in São Paulo city, Brazil

Piperaceae species have been placed among the basal angiosperm and are adapted to a variety of habitats including moist forests, secondary vegetation and dry high lands. The major anatomical/morphology features are of small trees, vines, and shrubs for Piper species, while the epiphytic and succulent characteristics are predominant forms among Peperomia species. Their secondary chemistry can be mostly represented by amides, phenylpropanoids/lignoids, and chromenes in addition to a phletoria of biosynthetically mixed-origin secondary compounds. Although several amides and lignans are known as insecticides, several phytophagous insects, among which some considered pests of economic importance, have been observed feeding vigorously on Piperaceae species. Herein we describe the feeding preferences of fourteen phytophagous species of Coleoptera, Lepidoptera and Hemiptera over approximately fifty Piperaceae species observed in São Paulo, SP, Brazil, in a long-term basis.

Trypanocidal activity of Piper arboreum and Piper tuberculatum (Piperaceae)

In the scope of our ongoing research on bioactive agents from Brazilian flora, twenty-four extracts and fractions obtained from Piper arboreum Aub. and Piper tuberculatum Jacq. (Piperaceae) were screened for trypanocidal activity by using MTT colorimetric assay. The strongest activity was found in hexane fractions from the leaves of P. arboreum (IC50= 13.3 µg/ mL) and P. tuberculatum (IC50 = 17.2 µg/mL). Hexane fractions of the fruits of P. tuberculatum and P. arboreum showed potent toxic effects on epimastigote forms of Trypanosoma cruzi, with values of IC50 (µg/mL) of 32.2 and 31.3, respectively. Additionally, the phytochemical study of the hexane fraction of P. arboreum leaves furnished two pyrrolidine amides, piperyline (1) and 4,5-dihydropiperyline (2), which could be responsible, at least in part for the observed antiprotozoal activity.

omega-Transaminases as efficient biocatalysts to obtain novel chiral selenium-amine ligands for Pd-catalysis

omega-Transaminases have been evaluated as biocatalysts in the reductive amination of organoselenium acetophenones to the corresponding amines, and in the kinetic resolution of racemic organoselenium amines. Kinetic resolution proved to be more efficient than the asymmetric reductive amination. By using these methodologies we were able to obtain both amine enantiomers in high enantiomeric excess (up to 99%). Derivatives of the obtained optically pure o-selenium 1-phenylethyl amine were evaluated as ligands in the palladium-catalyzed asymmetric alkylation, giving the alkylated product in up to 99% ee.

Antimicrobial activity of Piper arboreum and Piper tuberculatum (Piperaceae) against opportunistic yeasts

In the scope of our ongoing research on bioactive agents from natural sources, 24 extracts and fractions obtained from Piper arboreum Aub. and Piper tuberculatum Jacq. ( Piperaceae) were screened for antifungal activity by using broth microdilution method. The current investigation reveals that P. arboreum extracts and fractions were more effective against Candida krusei and Candida parapsilosis than Cryptococcus neoformans. The growth of Candida albicans was weakly affected by all the tested extracts and fractions. The strongest effects were observed for hexane and ethyl acetate fractions from leaves of P. arboreum, with MIC values ( in mu g/ml) of 15.6 and 31.2 mu g/ml against C. krusei, respectively. Additionally, phytochemical investigation of the hexane fraction of P. arboreum leaves furnished 3 pyrrolidine amides; piperyline, 4,5-dihydropiperyline and tetrahydropiperyline, which could be responsible, at least in part for the observed antifungal activity. The most active compound, tetrahydropiperyline, displayed MIC values of 15.6 mu g/ml against C. krusei, C. parapsilosis and C. neoformans.

Study of Salmonella typhimurium mutagenicity assay of (E)-piplartine by the Ames test

Phytochemical studies carried out with Piperaceae species have shown great diversity of secondary metabolites among which are several displayed considerable biological activities. The species Piper tuberculatum has been intensively investigated and a series of amides have been described. For instance, (E)-piplartine showed significant cytotoxic activity against tumor cell lines, especially human leukemia cell lines; antifungal activity against Cladosporium species; trypanocidal activity and others. Considering the popular use of P. tuberculatum and the lack of pharmacological studies regarding this plant species, the mutagenic and antimutagenic effect of (E)-piplartine was evaluated by the Ames test, using the strains TA97a, TA98, TA100 and TA102 of Salmonella typhimurium. No mutagenic activity was observed for this compound.

Dodigen 213-N as corrosion inhibitor for ASTM 1010 mild steel in 10% HCL

This article describes a study of the behavior of a mixture of amines and amides, commercially known as Dodigen 213-N (D-213 N), as a corrosion inhibitor for ASTM 1010 mild steel in 10% w/w HCl solution. The concentration range used was 1 x 10(-5) M to 8 x 10(-4) M. The weight loss and electrochemical techniques used were corrosion potential measurement, anodic and cathodic polarization curves, and electrochemical impedance spectroscopy (EIS). The solution temperature was 50 +/- A 1 A degrees C and it was naturally aerated. The corrosion potential values shifted to slightly more positive values, thus indicating mixed inhibitor behavior. The anodic and cathodic polarization curves showed that D-213 N is an effective corrosion inhibitor, since both the anodic and the cathodic reactions were polarized in comparison with those obtained without inhibitor. For all concentrations the cathodic polarization curves were more polarized than the anodic ones. The inhibition efficiency was in the range 75-98%, calculated from values of weight loss and corrosion current density, i (corr), obtained by extrapolation of Tafel cathodic linear region.

Nucleophilic addition of potassium organotrifluoroborates to chiral cyclic N-acyliminium ions: stereoselective synthesis of functionalized N-heterocycles

The stereoselective nucleophilic addition of potassium aryl- and alkynyltrifluoroborates to cyclic N-acyliminium ion derivatives from N-benzyl-3,4,5-triacetoxy-2-pyrrolidinone, affording the respective 5-substituted 2-pyrrolidinone is described. The products were obtained in moderate to good yields and with preference for the syn diastereomer. (C) 2008 Elsevier Ltd. All rights reserved.

Piperamides and their derivatives as potential anti-trypanosomal agents

We describe herein an evaluation of the trypanocidal effect of eight piperamides (1-8) isolated from Piper tuberculatum bearing dihydropyridone, piperidine, and isobutyl moieties against epimastigote forms of Trypanosoma cruzi, the causative agent of Chagas` disease. Based on such results, three hydrogenated and two hydrolyzed derivatives (10-14) were prepared and evaluated as well. The dihydropyridone amides (1-3) displayed higher anti-trypanosomal activity. The (Z)-piplartine (1) showed higher activity with a 50% inhibition concentration (IC(50)) value of 10.5 mu M, almost four times more potent than the positive control, benznidazole (IC(50) = 42.7 mu M), and should be further evaluated as a suitable hit for the design of new antiprotozoal agents.

Biomimetic Oxidation of Piperine and Piplartine Catalyzed by Iron(III) and Manganese(III) Porphyrins

Synthetic metalloporphyrins, in the presence of monooxygen donors, are known to mimetize various reactions of cytochrome P450 enzymes systems in the oxidation of drugs and natural products. The oxidation of piperine and piplartine by iodosylbenzene using iron(III) and manganese(III) porphyrins yielded mono- and dihydroxylated products, respectively. Piplartine showed to be a more reactive substrate towards the catalysts tested. The structures of the oxidation products were proposed based on electrospray ionization tandem mass spectrometry.

Synthesis, mechanism of formation, and molecular orbital calculations of arylamidoximes

A simple and easy synthesis of ten arylamidoximes from arylnitriles and hydroxylamine is described. The formation of the arylamides has been observed to a much lesser extent in the present work. A new mechanism for the formation of arylamidoximes, as well as arylamides, from arylnitriles and hydroxylamine is suggested. Quantum mechanical calculations have been carried out to support this mechanism. The enthalpy of formation in conjunction with atomic charges of the reactants and intermediates helped to understand more about the generation of the products.