Diaryl ether and diaryl thioether syntheses on solid supports via copper (I)-mediated coupling.
An efficient method to synthesize diaryl ethers and thioethers on solid supports is described. Starting from immobilized phenols or arylhalides, coupling with an access of aryliodides/arylbromides or phenolic/thiophenolic substrates in solution was successful in the presence of CuCl and Cs(2)CO(3) as base. Coupling conditions known from solution-phase syntheses of diaryl ethers have been effectively modified and adapted to solid-phase synthesis. Optimized conditions enabled the coupling of sterically hindered and/or electronically deactivated aryl moieties. After coupling, a newly developed diversity-generating linker based on cinnamic acid allowed the diaryl ethers to be cleaved from the resin either via saponification/transesterification or via ozonolysis. Latter offers the possibility of generating several additional compounds by simple variation of the cleavage conditions. The target substances were generally isolated in good to excellent yields and high purities.
Chemical Constituents of Caesalpinia bonduc
This phytochemical investigation of Caesalpinia bonduc reported eight known compounds, namely threo-2,3-bis(4-hydroxy-3-methoxyphenyl)-3-methoxy-propanol (1), evofolin-B (2), trans-Linalool-3,6-oxide-β-D-glucopyranoside (3), 1-(2-methylbutyryl)phloroglucinol-glucopyranoside (4), 1-(3 methylbutyryl)phloroglucinol-glucopyranoside (5), (+)-isolariciresinol (6), protocatechuic acid (7), methyl gallate (8). The structures of these compounds were identified by 1D- and 2D- nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) and by comparison with those reported in the literature. Compound 2 exhibited significant cytotoxic effects against the HepG2 cell line with an IC50 value of 48.37±3.18 µM.
The Arab Spring: The End of Postcolonialism
* Introduction: The Arab Spring: The End of Postcoloniality * 1. Decentering the World: How the Arab Spring Unfolded * 2. Towards Liberation Geography * 3. A New Language of Revolt * 4. Discovering a New World * 5. From the Green Movement to the Jasmine Revolutions * 6. The center cannot hold * 7. The End of Postcolonialism * 8. Race, Gender, and Class in Transnational Revolutions * 9. Libya: The Crucible * 10. Delayed Defiance * Conclusion. The People Demand the Overthrow of the Regime