Kerr constants of amides and peptides

Molar Kerr contants _mK have been determined for N-methylacetamide, N-ethyl-acatamide, N-methylpropionamide, N-acetylglycine-N′-methylamide, N-acetyl-L -ala-nine-N′-methylamide, and N-acetyl-L -leucine-N′-methylamide from electric birefringence measurements on dilute solutions in dioxane. The resultes are compared with configurational averatges 〈_mK〉 calculated on the basis of conformational energies. Values of_mK calculated for various fixed confromations on the peptides vary over a wide range depending on the choice of conformation; hece, the configurational averages 〈_mK〉 are sensitive to smalll changes in the conformational enerey. Kerr constants are calculated for random coiled oligoglycine and oligoalanine peptides as functions of chain length. The Kerr constant is an especially acute index of the average conformation.     

Anti-inflammatory, antioxidant and analgesic amides

The synthesis of some new aryl acetic acids and amides and a pharmacochemical study and quantitative structure-activity relationships (QSAR) on them are described. The compounds were screened for their biological activity using the carrageenin induced rat paw oedema model and a significant inhibition of oedema occurred (44.1-80.1%) at a concentration of 0.01 mmol/1 kg. The analgesic activity, based on the inhibition of acetic acid-induced writhing in rats was also found to be significant. The compounds were found to interact with the stable free radical 1,1-diphenylhydrazyl DPPH and with DMSO (for hydroxyl radicals). The compounds were screened for radical scavenging activity with the xanthine/xanthine oxidase system for O2-* and for inhibition of soybean lipoxygenase (LOX). The results are discussed in terms of the structural and physicochemical characteristics of the compounds.     

Piperidides and other amides from Achillea species

The investigation of the roots of four Achillea species afforded, in addition to known ones eight new amides most of them being piperidides. The structures were elucidated by spectrocopic methods. The chemotaxonomic importance of the amides is discussed briefly.     

Depolarized light scattering by amides and peptides

The Rayleigh ratios R_H have been measured for the depolarized scattering dilute solutions of N-ethylacetamide (EA), N-methylpropionamide (MP), and N-acetyl-pyrrolidine (AP) in P-dioxane, and dilute aqueous solutions of N-methylacetamide (MA), N,N-dimethylacetamide (DMA), EA, and MP. Squares of the optical anisot-ropies γ of the amides are obtained through extrapolation of these mesurements to infinite dilution. Values of γ² found for EA and MP in dioxane are in good agreement with calculations based principally on the previously evaluated polarizability tensor of the amide group in conjunction with C? C and C? H bond polarizabilities. The calculations also involve averaging over all conformations, each being weighted according to the estimated conformational energy. The mean-squared optical anisotropies (γ²) of the oligoglycines and oligoalanines are calculated by similarly averaging over all skeletal conformations. The anistropic polarizability tensor \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \alpha $\end{document} for the prolyl structural unit is derived for γ² for AP. The much larger optical anisotropies exhibited by the amides when dissolved in water as compared with those observed in dixane are discussed.     

Phenylpropanoid amides and phenylethanols from Nanophyton erinaceum

Phytochemical investigation of the aerial parts of Nanophyton erinaceum (Pall.) Bunge led to the isolation and identification of one new (1) and eight known phenylpropanoid amides (2–9), four phenylethanols (10–13), two flavonoids (14–15) and one coumarin (16). This is the first report of these isolates from the genus Nanophyton and their chemotaxonomic significance is summarized herein.     

Spilanthol-related amides from Acmella ciliata

From the flower heads of Acmella ciliata amides closely related to spilanthol were isolated. They possess isobutylamine, 2-phenylethylamine and 2-methylbutylamine parts. In the acidic part deca-2E,6Z,8E-trienoic acid, known from spilanthol, and its 2,3-dihydro derivative were found. Two compounds bear ester groups, a novelty for unsaturated amides. The structures were elucidated by means of high field ¹H NMR and high resolution mass spectrometry.     

Further amides from Echinacea purpurea

The aerial parts of Echinacea purpurea afforded, in addition to known compounds, five further highly unsaturated amides and a derivative of linolen     

Two amides from Piper amalago

The hexane extracts of the roots of Piper amalago afforded two trans-cinnamoylamides, 2-methoxy-4,5-methylenedioxy-trans-cinnamoyl piperidide and pyrrolidide.     

Stereoselective synthesis of N-galactofuranosyl amides

α- or β-Galactofuranosyl (Galf) amides can be synthesized with high stereoselectivity by traceless Staudinger ligation starting from unprotected β-galactofuranosyl azide or tetra-O-acetyl-β-galactofuranosyl azide, respectively. The resulting Galf amides are hitherto unknown molecules, with interesting potential as inhibitors of mycobacterial growth.