Ioana Maria Ungureanu

Modulation of bitter taste perception by a small molecule hTAS2R antagonist

Human bitter taste is mediated by the hTAS2R family of G protein-coupled receptors. The discovery of the hTAS2Rs enables the potential to develop specific bitter receptor antagonists that could be beneficial as chemical probes to examine the role of bitter receptor function in gustatory and nongustatory tissues. In addition, they could have widespread utility in food and beverages fortified with vitamins, antioxidants, and other nutraceuticals, because many of these have unwanted bitter aftertastes. We employed a high-throughput screening approach to discover a novel bitter receptor antagonist (GIV3727) that inhibits activation of hTAS2R31 (formerly hTAS2R44) by saccharin and acesulfame K, two common artificial sweeteners. Pharmacological analyses revealed that GIV3727 likely acts as an orthosteric, insurmountable antagonist of hTAS2R31. Surprisingly, we also found that this compound could inhibit five additional hTAS2Rs, including the closely related receptor hTAS2R43. Molecular modeling and site-directed mutagenesis studies suggest that two residues in helix 7 are important for antagonist activity in hTAS2R31 and hTAS2R43. In human sensory trials, GIV3727 significantly reduced the bitterness associated with the two sulfonamide sweeteners, indicating that hTAS2R antagonists are active in vivo. Our results demonstrate that small molecule bitter receptor antagonists can effectively reduce the bitter taste qualities of foods, beverages, and pharmaceuticals.

The reactivity of N-tosylphenylaziridine versus N-tosylphenylazetidine in heterocyclization reactions

N-Tosylaziridine (1) and N-tosylazetidine (2) react as 1,3 and 1,4 masked dipoles with electron rich alkenes, respectively, either under kinetic or thermodynamic control. The reactivity of the new aza oxo [4.4.0] 9, a precursor of N-tosyliminium, was exploited for the preparation of stereodefined substituted piperidines.

Phenylaziridine as a 1,3-dipole. Application to the synthesis of functionalized pyrrolidines

Abstract ce:simple-parahenylaziridine 1 in the presence of an appropriate Lewis acid reacts as a 1,3-dipole. The cyclocondensation of 1 with DHP in the presence of BF 3 ·Et 2 O produced the azaoxa[3.2.0] cycloadducts 4a–4b . The reactivity of the corresponding N -tosyliminium ions was explored.

From phenylaziridine to phenylkainoids. A formal synthesis of (±)-phenylkainic acid☆

Abstract The condensation of phenylaziridines ( 3a/3b ) with 3-cyclopentenylsilane ( 4 ) in presence of BF 3 .Et 2 O yielded amino-cyclopentenyl adducts ( 5a–8a ) and ( 5b–8b ). Heterocyclisation of the ω-amino-olefins assisted by Pd(OAc) 2 afforded the azabicyclo adducts 2a/2′a and 2b/2′b . Oxidation of the internal double bond, followed by epimerization at C(2) was realized by KH in presence of 18-crown-6 yielding 11 , the fully protected phenylkainic acid.

2-Phenyl-N-tosylazetidine as a formal 1,4dipole precursor

N-Tosyl-2-phenylazetidine 1 in the presence of BF3·Et2O reacts as a formal 1,4 dipole with various activated or non activated alkenes.