Characteristics of Ramachandran maps of L-alanine diamides as computed by various molecular mechanics, semiempirical and ab initio MO methods. A search for primary standard of peptide conformational stability

The optimized geometries and relative energies obtained by four force field and two semi-empirical methods were compared with ab initio results computed for formyl-L-alaninamide. Not all methods yielded the same number of minimum energy conformers. Furthermore, while the optimized geometries of the conformers found were comparable, the computed relative energies varied substantially. Also, the force field calculations produced Ramachandran maps that did not even have the appearance of the ab initio Ramachandran map. Correlating the ab initio relative energies (Delta E) or free energy (Delta G) with the log of relative populations, In(p(x)/p(gamma L)), led to linear relationships from which four conformers deviated; two of them (alpha(L) and epsilon(L)) were overly destabilized and two of them (gamma(L) and gamma(D)) were over-stabilized. It is suggested that, after such deviations are corrected, a primary standard may be obtained that might be useful in further investigations related to force-field parametrization as well as protein folding. (C) 1998 Elsevier Science B.V. All rights reserved

A Conformational Study of Flexible Cyclic Compounds (Hydrocarbon Rings of 9-12 Members)

We report here a conformational study of cyclic flexible compounds (rings with 9-12 members). Two methods of systematic search for the minima were used. The results were compared with those obtained using other exploratory methods

A Conformational Study of Flexible Cyclic Compounds (Hydrocarbon Rings of 9-12 Members)

Abstract: We report here a conformational study of cyclic flexible compounds (rings with 9-12 members). Two methods of systematic search for the minima were used. The results were compared with those obtained using other exploratory methods

The Importance of Keto-Enol Forms of Arylpropanoids Acting as Antifungal Compounds

We report here the importance of a keto-enol equilibrium of an arylpropanoid series acting as antifungal agents. An interesting relationship between ln MIC, ∆E enolization and net atomic charges was found. Two compounds were synthesized and their MIC evaluated in order to prove the above relationship

New medicines inspirated in Annonaceae = Nuevos fármacos inspirados en Annonáceas

Active secondary metabolites (ASM) play a highly significant role in the drug discovery. Natural complex chemical skeleton such as statins isolated from Aspergillus terreus, or acetogenins specific from Annonaceae family, are not able to be invented in any laboratory. The ASM isolated from Annonaces, especially acetogenins and isoquinoline alkaloids should be considered as a source of continuous inspiration for the chemists, the pharmacologists and all researchers that are interested in discovering a new drug family. --- Los metabolitos secundarios activos (MSA) juegan un papel importante en el descubrimiento de nuevos medicamentos. Moléculas naturales con esqueletos complejos, tales como las estatinas aisladas de Aspergillus terreus, o las acetogeninas específicas de la familia Annonaceae, no hubieran podido ser inventadas en ningún laboratorio. Los MSA aislados en Annonaceae, especialmente las acetogeninas y los alcaloides isoquinoleínicos, pueden ser considerados como fuente constante de inspiración para químicos, farmacólogos y para todos los investigadores interesados en el descubrimiento de una nueva familia de medicamentos