Exposure of 3,3,6-trimethylcyclohex-5-ene-1,2,4-trione to catalytic amounts of Lewis acids revealed two disparate reactions in the presence of cyclopentadiene. The expected cycloaddition was found to be reversible for the title compound, and transfer hydrogenation was the preferred pathway over long periods of time. Other tested substrates were able to undergo facile cycloaddition with considerable yields and without the parallel reduction.

A library of 91 heterocyclic compounds composed of 16 distinct scaffolds has been synthesized through a sequence of phosphine-catalyzed ring-forming reactions, Tebbe reactions, Diels–Alder reactions, and, in some cases, hydrolysis. This effort in diversity-oriented synthesis produced a collection of compounds that exhibited high levels of structural variation both in terms of stereochemistry and the range of scaffolds represented. A simple but powerful sequence of reactions thus led to a high-diversity library of relatively modest size with which to explore biologically relevant regions of chemical space. From this library, several molecules were identified that inhibit the migration and invasion of breast cancer cells and may serve as leads for the development of antimetastatic agents.

Raf kinase inhibitor protein (RKIP) regulates a number of cellular processes, including cell migration. Exploring the role of RKIP in cell adhesion, we found that overexpression of RKIP in Madin-Darby canine kidney (MDCK) epithelial cells increases adhesion to the substratum, while decreasing adhesion of the cells to one another. The level of the adherens junction protein E-cadherin declines profoundly, and there is loss of normal localization of the tight junction protein ZO-1, while expression of the cell–substratum adhesion protein β1 integrin dramatically increases. The cells also display increased adhesion and spreading on multiple substrata, including collagen, gelatin, fibronectin and laminin. In three-dimensional culture, RKIP overexpression leads to marked cell elongation and extension of long membrane protrusions into the surrounding matrix, and the cells do not form hollow cysts. RKIP-overexpressing cells generate considerably more contractile traction force than do control cells. In contrast, RNA interference-based silencing of RKIP expression results in decreased cell–substratum adhesion in both MDCK and MCF7 human breast adenocarcinoma cells. Treatment of MDCK and MCF7 cells with locostatin, a direct inhibitor of RKIP and cell migration, also reduces cell–substratum adhesion. Silencing of RKIP expression in MCF7 cells leads to a reduction in the rate of wound closure in a scratch-wound assay, although not as pronounced as that previously reported for RKIP-knockdown MDCK cells. These results suggest that RKIP has important roles in the regulation of cell adhesion, positively controlling cell–substratum adhesion while negatively controlling cell–cell adhesion, and underscore the complex functions of RKIP in cell physiology. J. Cell. Biochem. 103: 972–985, 2008. © 2007 Wiley-Liss, Inc.