Peptide damage under Fenton conditions is sequence-dependent.

Peptides with two or more acidic amino acids are damaged to a greater extent than other peptides under Fenton conditions as revealed by treating a 29791 membered one-bead-one-compound peptide library with FeCl(3), sodium ascorbate and hydrogen peroxide.

Flexible but with a defined turn-influence of the template on the binding properties of two-armed receptors.

Combinatorial binding studies revealed that the di(trans-4-aminoproline)diketopiperazine is an ideal template for two-armed receptors with highly selective binding properties towards peptides. It is not only superior to structurally very different diamines but also to the diastereomeric di(cis-4-aminoproline)diketopiperazine. These empiric results are rationalized by the analysis of the conformation of the diastereomeric diketopiperazines in the solid state, by X-ray crystal structure analysis, as well as by NMR studies in solution: to observe highly selective binding, the template needs to be not only conformationally rigid but it must have a specific turn geometry.

C-5-substituted antifeedant silphinene sesquiterpenes from Senecio palmensis.

The new sesquiterpenes, 5alpha-senecioyloxysilphinen-3-one (5), 5alpha-tigloyloxysilphinen-3-one (7), and 3beta-hydroxy-5alpha-angeloyloxysilphinene (8), and the known compounds (6S)-2,10-bisaboladien-1-one (1), 6,7-epoxy-3(15)-caryophyllene (2), 6,7-epoxy-2,9-humuladiene (3), 5alpha-angeloyloxysilphinen-3-one (4), and 5alpha-acetoxysilphinen-3-one (6) were isolated from bioactive fractions of Senecio palmensis. The structures of these compounds were established by spectroscopic analysis and chemical evidence. The semisynthetic analogues silphinen-3,5-dione (9), 5alpha-hydroxysilphinen-3-one (10), 5beta-hydroxysilphinen-3-one (11), 5beta-acetoxysilphinen-3-one (12), and 5beta-isobutyryloxysilphinen-3-one (13) were generated to carry out a structure-activity study on the antifeedant action of these molecules against several divergent insect species.