Analysis of ergonomics problems contact-centers

The analysis of the ergonomic problems of the contact center. It allocates main factors of influence on man- operator

Nature of Amide Carbonyl−Carbonyl Interactions in Proteins

Nature of Amide Carbonyl−Carbonyl Interactions in Protein

Crystal structures of two 1,3-thiazolidin-4-one derivatives featuring sulfide and sulfone functional groups

The crystal structures of two closely related compounds, 1-cyclohexyl-2-(2-nitrophenyl)-1,3-thiazolidin-4-one, C15H18N2O3S, (1) and 1-cyclohexyl-2-(2-nitrophenyl)-1,3-thiazolidin-4-one 1,1-dioxide, C15H18N2O5S, (2), are presented. These compounds are comprised of three types of rings: thiazolidinone, nitrophenyl and cyclohexyl. In both structures, the rings are close to mutually perpendicular, with interplanar dihedral angles greater than 80° in each case. The thiazolidinone rings in both structures exhibit envelope puckering with the S atom as flap and the cyclohexyl rings are in their expected chair conformations. The two structures superpose fairly well, except for the orientation of the nitro groups with respect to their host phenyl ring, with a difference of about 10° between 1 and 2. The extended structure of 1 has two kinds of weak C—H...O interactions, giving rise to a closed ring formation involving three symmetry-related molecules. Structure 2 has four C—H...O interactions, two of which are exclusively between symmetry-related thiazolidinone dioxide moieties and have a parallel `give-and-take-fashion' counterpart. In the other two interactions, the nitrophenyl ring and the cyclohexane ring each offer an H atom to the two O atoms on the sulfone group. Additionally, a C—H...π interaction between a C—H group of the cyclohexane ring and the nitrophenyl ring of an adjacent molecule helps to consolidate the structure

Synthesis of 5-Fluoro- and 5-Hydroxymethanoprolines via Lithiation of <i>N</i>-BOC-methanopyrrolidines. Constrained C^γ-Exo and C^γ-Endo Flp and Hyp Conformer Mimics

Proline derivatives with a C^γ-exo pucker typically display a high amide bond trans/cis (<i>K</i>_T/C) ratio. This pucker enhances n→π* overlap of the amide oxygen and ester carbonyl carbon, which favors a trans amide bond. If there were no difference in n→π* interaction between the ring puckers, then the correlation between ring pucker and <i>K</i>_T/C might be broken. To explore this possibility, proline conformations were constrained using a methylene bridge. We synthesized discrete gauche and anti 5-fluoro- and 5-hydroxy-<i>N</i>-acetylmethanoproline methyl esters from 3-syn and 3-anti fluoro- and hydroxymethanopyrrolidines using directed α-metalation to introduce the α-ester group. NBO calculations reveal minimal n→π* orbital interactions, so contributions from other forces might be of greater importance in determining <i>K</i>_T/C for the methanoprolines. Consistent with this hypothesis, greater trans amide preferences were found in CDCl₃ for anti isomers en-MetFlp and en-MetHyp (72–78% trans) than for the syn stereoisomers ex-MetFlp and ex-MetHyp (54–67% trans). These, and other, <i>K</i>_T/C results that we report here indicate how substituents on proline analogues can affect amide preferences by pathways other than ring puckering and n→π* overlap and suggest that caution should be exercised in assigning enhanced pyrrolidine C^γ-exo ring puckering based solely on enhanced trans amide preference