A strategy for the synthesis of natural and non-natural 5-deoxy-6,7-dihydrocurcuminoids (diarylheptanoids) was developed for the preparation of 14 compounds with varying aromatic substituent patterns and a different functionality in the aliphatic seven-carbon chain. The in vitro protective activity against glutamate-induced neuronal cell death was examined in the murine hippocampal cell line HT-22 to find structural motifs responsible for neuroprotective effects in vitro. Among the tested compounds the ferulic acid-like unit, present in the structures of (E)-1,7-bis(4-hydroxy-3-methoxyphenyl)hept-1-en-3-one (5) and (E)-1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)hept-1-en-3-one (7), appeared to be an important feature for protection against glutamate-induced neurotoxicity. Both compounds demonstrated significant neuroprotective activity in a concentration range between 1 and 25 μM without showing toxic effects in a cytotoxicity assay with HT-22 cells. Furthermore, (E)-1,7-bis(3,4-dihydroxyphenyl)hept-1-en-3-one (9), exhibiting a caffeic acid-like structural motif, displayed a neuroprotective activity at a nontoxic concentration of 25 μM. In contrast, (1E,6E)-1,7-bis(3,4-dihydroxyphenyl)hepta-1,6-diene-3,5-dione (4, di-O-demethylcurcumin) showed mainly cytotoxic effects. A corresponding single-ring analogue that contains the ferulic acid-like unit as an enone was not active.
In this work, we try to hydrogenate selectively phenylacetylene to styrene and 3-phenylpropyne to allylbenzene using immobilized or pure Wilkinson's catalyst. The catalyst was immobilized using two approaches-immobilization using ionic exchange and immobilization using covalent bonding. In the first case, the smectite minerals (hectorite and montmorillonite) were used as the supports. In the second case, MCM-41 and SBA-15 were used as the supports. Both types of immobilization were successful and the solid products were characterized. For the covalent bond formation, it was necessary to first modify the surface of the silica material. The modification was carried out using two substances, one adding an amino group to the silica material, and the second adding a phenyl group to the material. The selectivity of hydrogenation of both substances was higher using heterogeneous catalyst in the case of phenylacetylene. In the case of phenylpropyne, no difference in selectivity using Wilkinson's catalyst in homogeneous or heterogeneous arrangement was observed. The type of immobilization has no influence on either activity or selectivity of catalyst.
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