Transition metals in organic synthesis: Highlights for the year 2003

Size-Dependent Catalytic Activity and Fate of Palladium Nanoparticles in Suzuki-Miyaura Coupling Reactions

Stable, catalytically active palladium nanoparticles of various average diameters (1.9-7.4 nm) have been synthesized and characterized by X-ray diffraction, spectroscopy, and microscopy techniques to demonstrate remarkable size-dependent and renewed catalytic activity toward the Suzuki-Miyaura coupling reaction in green protocol. The catalytic activity is found to depend on the amount of the reducing agent, stabilizer-precursor ratio, solvent composition, and aryl halides used. The product obtained by this reaction is characterized by ¹H NMR, ¹³C NMR, and IR spectroscopy analyses. A newly developed kinetic equation illustrates that while the catalyst particles of the lowest dimension are gradually exposed to the reactants and hence activated due to partial removal of capping polymer from the catalyst surface, others are deactivated due to agglomeration during the progress of the reaction, as conformed by the microscopic profiles of the used and unused catalysts.

Versatile synthesis and biological evaluation of novel 3'-fluorinated purine nucleosides

A unified synthetic strategy accessing novel 3'-fluorinated purine nucleoside derivatives and their biological evaluation were achieved. Novel 3'-fluorinated analogues were constructed from a common 3'-deoxy-3'-fluororibofuranose intermediate. Employing Suzuki and Stille cross-coupling reactions, fifteen 3'-fluororibose purine nucleosides 1-15 and eight 3'-fluororibose 2-chloro/2-aminopurine nucleosides 16-23 with various substituents at position 6 of the purine ring were efficiently synthesized. Furthermore, 3'-fluorine analogs of natural products nebularine and 6-methylpurine riboside were constructed via our convergent synthetic strategy. Synthesized nucleosides were tested against HT116 (colon cancer) and 143B (osteosarcoma cancer) tumor cell lines. We have demonstrated 3'-fluorine purine nucleoside analogues display potent tumor cell growth inhibition activity at sub- or low micromolar concentration.