Single point binding ruthenium Lewis acid catalysts [Ru(acetone)(S,S)-BIPHOP-F)Cp][SbF(6)] ((S,S)-1b) and [Ru(acetone)(S,S)-BIPHOP-F)(indenyl)][SbF(6)] ((S,S)-1c) efficiently catalyze intramolecular Diels-Alder (IMDA) reactions under mild conditions to afford the endo cycloaddition products as the major product in excellent yields with high diastereo- and enantioselectivities.

One-point binding chiral ruthenium Lewis acids incorporating the C(2)-symmetric electron-poor bidentate phosphinite ligand BIPHOP-F and a Cp or an indenyl 'roof' can efficiently catalyze asymmetric intramolecular Diels-Alder reactions of trienes to form bicyclic adducts with good to excellent asymmetric induction. This reaction forms the key step in a total synthesis of ent-ledol in 96% ee. The synthesis also helps to clarify the stereochemical assignment of ledol and inconsistencies in the measured optical rotation.

Background/purpose The colonization of microorganisms onto denture bases is one common problem that can contribute to oral diseases. Herein, three food preservatives, including zinc oxide, potassium sorbate, and sodium metabisulfite were introduced as anti-microbial additives into a heat-polymerized poly(methyl methacrylate) (PMMA). Materials and methods Relative microbial reductions of the modified PMMA resins against Staphylococcus aureus , Pseudomonas aeruginosa , and Candida albicans were evaluated. The in vitro cytotoxicity of the materials was measured against mouse fibroblast L929 cells. A three-point flexural test was performed to determine a flexural strength and modulus properties of the materials. Results The incorporation of all preservative agents into the material diminished the microbial growth of three microbial species. The PMMA resin combined with sodium metabisulfite exhibited the greatest anti-microbial activity that reduced almost all bacterial cells and about 40% of C. albicans . All modified resins showed no significant cytotoxicity against L929 cells. The addition of food preservatives did not significantly alter the flexural strength of the PMMA resin (∼84–92 MPa). However, the flexural modulus of the PMMA incorporated with food preservatives (∼2,024–2,144 MPa) was significantly lower than the unmodified PMMA. Conclusion Three food preservatives, especially sodium metabisulfite, could be applied as anti-microbial additives into the denture base resin. The PMMA incorporated with the additives did not show cytotoxicity. Although, the addition of the food preservatives altered the mechanical properties, the materials still provided acceptable flexural properties.

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The reaction of masked 5-alkylidene-2-cyclopentenones with aldehydes catalyzed by tributylphosphine in the presence of phenol provided the corresponding Morita-Baylis-Hillman adducts, which were subjected to flash vacuum pyrolysis to afford 5-alkylidene-2-(hydroxyalkyl)-2-cyclopentenones.