Sol–gel reactions have been performed within porous polymer bead templates with diameters of 15 or 30 μm. Subsequent removal of the organic template gives porous silica and titania spheres. The Figure shows an example of a broken titania sphere and its inner porosity. This technique results in porous inorganic spheres that are monodisperse and non‐aggregated.

Guggulsterone 1, the active principle of guggulipid, has been used in ethnic medicine for thousands of years for its antinflammatory and antilipidemic activities. The activities of 1 are apparently mediated by its interaction with an array of nuclear receptors, including endocrine steroid receptors and metabolic lipid receptors. Although relatively weak, the activity at the metabolic farnesoid X receptor (FXR) is particularly intriguing, as 1 is, so far, the only antagonist known for this receptor, with a peculiar ability of gene selective modulation. We report here a systematic study aimed at identifying the potential binding pocket of 1 at FXR. Although 1 could be docked into the canonical binding site, we identified a novel, so far undescribed binding pocket, localized near the loop region between helix 1 and helix 2. This novel binding pocket may explain some of the peculiar characteristics of 1 when acting at FXR.

Carbamate derivatives of bile acids were synthesized with the aim of systematically exploring the potential for farnesoid X receptor (FXR) modulation endowed with occupancy of the receptor's back door, localized between loops H1-H2 and H4-H5. Since it was previously shown that bile acids bind to FXR by projecting the carboxylic tail opposite the transactivation function 2 (AF-2, helix 12), functionalization of the side chain is not expected to interfere directly with the orientation of H12 but can result in a more indirect way of receptor modulation. The newly synthesized compounds were extensively characterized for their ability to modulate FXR function in a variety of assays, including the cell-free fluorescence resonance energy transfer (FRET) assay and the cell-based luciferase transactivation assay, and displayed a broad range of activity from full agonism to partial antagonism. Docking studies clearly indicate that the side chain of the new derivatives fits in a so far unexploited receptor cavity localized near the "back door" of FXR. We thus demonstrate the possibility of achieving a broad FXR modulation without directly affecting the H12 orientation.

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