Synthesis of 2,2,4,4-Tetramethyl-N,N′-bis(2,6-dimethylphenyl)cyclobutane-1,3-diimine, a Unique Compound from Arundo donax, and Its Analogues to Test Their Antifeedant Activity Against the Boll Weevil, Anthonomus grandis
2,2,4,4-Tetramethyl-N,N′-bis(2,6-dimethylphenyl) cyclobutane-1,3-diimine (1), which was isolated from the Thai plant Arundo donax as an antifeedant against the boll weevil (Anthonomus grandis), and its analogues (9-13) were synthesized and shown to possess no remarkable antifeedant activity of practical interest.
Synthesis of -Chloroimines
Synthese de β-chloro-aldimines et -cetimines par reaction de composes β-chlorocarbonyles avec des alkylamines
Collagen dynamics in articular cartilage under osmotic pressure
Cartilage is a complex biological tissue consisting of collagen, proteoglycans and water. The structure and molecular mobility of the collagen component of cartilage were studied by 13C solid‐state NMR spectroscopy as a function of hydration. The hydration level of cartilage was adjusted between fully hydrated (∼80 wt% H2O) and highly dehydrated (∼30 wt% H2O) using the osmotic stress technique. Thus, the conditions of mechanical load could be simulated and the response of the tissue macromolecules to mechanical stress is reported. From the NMR measurements, the following results were obtained. (i) Measurements of motionally averaged dipolar 1H–13C couplings were carried out to study the segmental mobility in cartilage collagen at full hydration. Backbone segments undergo fast motions with amplitudes of ∼35° whereas the collagen side‐chains are somewhat more mobile with amplitudes between 40 and 50°. In spite of the high water content of cartilage, collagen remains essentially rigid. (ii) No chemical shift changes were observed in 13C cross‐polarization magic angle spinning spectra of cartilage tissue at varying hydration indicating that the collagen structure was not altered by application of high osmotic stress. (iii) The 1H–13C dipolar coupling values detected for collagen signals respond to dehydration. The dipolar coupling values gradually increase upon cartilage dehydration, reaching rigid limit values at ∼30 wt% H2O. This indicates that collagen is essentially dehydrated in cartilage tissue under very high mechanical load, which provides insights into the elastic properties of cartilage collagen, although the mechanical pressures applied here exceed the physiological limit. Copyright © 2006 John Wiley & Sons, Ltd.