A catalytic amount of ruthenium(III) acetylacetonate (2 mol%) [Ru(acac)3] enables solvent-free tetrahydropyranylation of different types of alcohols and phenols at ambient temperature in moderate to excellent yields. Notably, selective monoprotection of diols can be achieved chemoselectively. Furthermore, the catalyst could be recovered and reused if necessary.Key words: tetrahydropyranyl ethers, protecting groups, ruthenium(III) acetylacetonate, alcohols, thiols.
Eleven chalcone derivatives have been tested for their inhibitory effects on platelet aggregation in rabbit platelet suspension and the activation of mast cells and neutrophils.
Arachidonic acid-induced platelet aggregation was potently inhibited by almost all the compounds and some also had a potent inhibitory effect on collagen-induced platelet aggregation and cyclooxygenase. Some hydroxychalcone derivatives showed strong inhibitory effects on the release of β-glucuronidase and lysozyme, and on superoxide formation by rat neutrophils stimulated with the peptide fMet-Leu-Phe (fMLP). We found that the anti-inflammatory effect of 2′,5′-dihydroxychalcone was greater than that of trifluoperazine. 2′,5′-Dihydroxy and 2′,3,4,4′-tetrahydroxyl chalcones, even at low concentration (50 μm), tested in platelet-rich plasma from man almost completely inhibited secondary aggregation induced by adrenaline.
These results suggest that the anti-platelet effects of the chalcones are mainly a result of inhibition of thromboxane formation.