115022-93-0Relevant academic research and scientific papers
Dioxygen activation with molybdenum complexes bearing amide-functionalized iminophenolate ligands
Zwettler, Niklas,Ehweiner, Madeleine A.,Schachner, J?rg A.,Dupé, Antoine,Belaj, Ferdinand,M?sch-Zanetti, Nadia C.
, (2019)
Two novel iminophenolate ligands with amidopropyl side chains (HL2 and HL3) on the imine functionality have been synthesized in order to prepare dioxidomolybdenum(VI) complexes of the general structure [MoO2L2] featuring pendant internal hydrogen bond donors. For reasons of comparison, a previously published complex featuring n-butyl side chains (L1) was included in the investigation. Three complexes (1-3) obtained using these ligands (HL1-HL3) were able to activate dioxygen in an in situ approach: The intermediate molybdenum(IV) species [MoO(PMe3)L2] is first generated by treatment with an excess of PMe3. Subsequent reaction with dioxygen leads to oxido peroxido complexes of the structure [MoO(O2)L2]. For the complex employing the ligand with the n-butyl side chain, the isolation of the oxidomolybdenum(IV) phosphino complex [MoO(PMe3)(L1) 2] (4) was successful, whereas the respective Mo(IV) species employing the ligands with the amidopropyl side chains were found to be not stable enough to be isolated. The three oxido peroxido complexes of the structure [MoO(O2)L2] (9-11) were systematically compared to assess the influence of internal hydrogen bonds on the geometry as well as the catalytic activity in aerobic oxidation. All complexes were characterized by spectroscopic means. Furthermore, molecular structures were determined by single-crystal X-ray diffraction analyses of HL3, 1-3, 9-11 together with three polynuclear products {[MoO(L2) 2]2 (μ-O)} (7), {[MoO(L2)] 4 (μ-O) 6} (8) and [C9H13N2O]4 [Mo8O26] 6OPMe3 (12) which were obtained during the synthesis of reduced complexes of the type [MoO(PMe3)L2] (4-6).
A Mechanism for bitter Taste Sensibility in Peptides
Ishibashi, Norio,Kouge, Katsushige,Shinoda,Ichizo,Kanehisa, Hidenori,Okai, Hideo
, p. 819 - 828 (2007/10/02)
To estimate the steric distance between the bitter taste determinant sites in peptides, some cyclic dipeptides, amino acid anilides, amino acid cyclohexylamides, and benzoyl amino acids were synthesized and their tastes were evaluated.The diketopiperazine ring of cyclic dipeptides acted as a bitter taste determinant site due to its hydrophobicity.The steric distance between 2 sites was estimated as 4.1 Angstroem from the molecule models of cyclic dipeptides composed of typical amino acids in the bitter peptides.Due to the hypothesis of two bitter taste determinant sites, which bind with the bitter taste receptor via a "binding unit" and a "stimulating unit," a mechanism for the bitterness in peptides was postulated.
