1. Synthesis of Novel 5-(N-Boc-N-Benzyl-2-aminoethyl)-7-oxo-4,7-dihydropyrazolo[1,5-a]pyrimidin-3-carboxamides and Their Inhibition of Cathepsins B and K
Branislav Lukić, Uroš Grošelj, Marko Novinec, Jurij Svete Acta Chim Slov. 2017 Dec;64(4):782-789. doi: 10.17344/acsi.2017.3421.
Eight novel 5-(N-Boc-N-benzyl-2-aminoethyl)-7-oxo-4,7-dihydropyrazolo[1,5-a]pyrimidin-3-carboxamides were prepared in three steps from methyl 3-amino-1H-pyrazole-4-carboxylate and methyl 5-(benzyl(tert-butoxycarbonyl)amino)-3-oxopentanoate. The synthetic procedure comprises cyclocondensation of the above starting compounds, hydrolysis of the ester, and bis(pentafluorophenyl) carbonate (BPC)-mediated amidation. Title carboxamides were tested for inhibition of cathepsins K and B. The N-butylcarboxamide 5a exhibited appreciable inhibition of cathepsin K (IC50 ~ 25 μM), while the strongest inhibition of cathepsin B was achieved with N-(2-picolyl)carboxamide 5c (IC50 ~ 45 μM).
2. Transition-Metal-Free Cleavage of CO
Marc Devillard, Bas de Bruin, Maxime A Siegler, J I van der Vlugt Chemistry. 2017 Oct 4;23(55):13628-13632. doi: 10.1002/chem.201703798. Epub 2017 Sep 7.
Tertiary silane 1H , 2-[(diphenylsilyl)methyl]-6-methylpyridine, reacts with tris(pentafluorophenyl)borane (BCF) to form the intramolecular pyridine-stabilized silylium 1+ -HBCF. The corresponding 2-[(diphenylsilyl)methyl]pyridine, lacking the methyl-group on the pyridine ring, forms classic N(py)→B adduct 2H -BCF featuring an intact silane Si-H fragment. Complex 1+ -HBCF promotes cleavage of the C≡O triple bond in carbon monoxide with double C-Csp2 bond formation, leading to complex 3 featuring a B-(diarylmethyl)-B-aryl-boryloxysilane fragment. Reaction with pinacol generates bis(pentafluorophenyl)methane 4 as isolable product, proving the transition-metal-free deoxygenation of carbon monoxide by this main-group system. Experimental data and DFT calculations support the existence of an equilibrium between the silylium-hydroborate ion pair and the silane-borane mixture that is responsible for the observed reactivity.
3. Graphene-Supported Pyrene-Modified Cobalt Corrole with Axial Triphenylphosphine for Enhanced Hydrogen Evolution in pH 0-14 Aqueous Solutions
Xialiang Li, Haitao Lei, Xiaojun Guo, Xueli Zhao, Shuping Ding, Xueqing Gao, Wei Zhang, Rui Cao ChemSusChem. 2017 Nov 23;10(22):4632-4641. doi: 10.1002/cssc.201701196. Epub 2017 Sep 21.
A cobalt complex of 5,15-bis(pentafluorophenyl)-10-(4)-(1-pyrenyl)phenyl corrole that contains a triphenylphosphine axial ligand (1-PPh3 ) was synthesized and examined as an electrocatalyst for the hydrogen evolution reaction (HER). If supported on graphene (G), the resulting 1-PPh3 /G material can catalyze the HER in aqueous solutions over a wide pH range of 0-14 with a high efficiency and durability. The significantly enhanced activity of 1-PPh3 /G, compared with that of its analogues 1-py/G (the Co-bound axial ligand is pyridine instead of triphenylphosphine) and 2-py/G (Co complex of 5,10,15-tris(pentafluorophenyl)corrole), highlights the effects of the pyrenyl substituent and the triphenylphosphine axial ligand on the HER activity. On one hand, the pyrenyl moiety can increase the π-π interactions between 1 and graphene and thus lead to a fast electron transfer from the electrode to 1. On the other hand, the triphenylphosphine axial ligand can increase the electron density (basicity) of Co and thus make the metal center more reactive to protons at the trans position through a so-called "push effect". This study concerns a significant example that shows the trans effect of the axial ligand on the HER, which has been investigated rarely. The combination of various ligand-design strategies in one molecule has been realized in 1-PPh3 to achieve a high catalytic HER performance. These factors are valuable to be used in other molecular catalyst systems.
