The chemically achiral title mol-ecule, [Ti(C(4)H(10)N)(2)(C(21)H(16)N(2))], crystallizes in the chiral space group P2(1). All three N atoms coordinating to the Ti(IV) atom adopt planar environments [sums of valence angles = 359.5 (6), 360.0 (7) and 360.0 (6)°], which is indicative of pπ-dπ donation from all of these N atoms to the metal and, thus, of the formal 18 e(-) nature of the complex. T...

Model reactions offer a chemical mechanism by which formation of a sulfenyl amide residue at the active site of the redox-regulated protein tyrosine phosphatase PTP1B protects the cysteine redox switch in this enzyme against irreversible oxidative destruction. The results suggest that 'overoxidation' of the sulfenyl amide redox switch to the sulfinyl amide in proteins is a chemically reversible...

Amide-amide hydrogen bonds have been implicated in directing protein folding and enhancing protein stability. Inversion transfer (13)C NMR spectroscopy and IR spectroscopy were used to compare the ability of various amide solvents and of water to alter the rate of the cis-trans isomerization of the prolyl peptide bond of Ac-Gly-[β,δ-(13)C]Pro-OMe and the amide I vibrational mode of [(13)C=O]Ac-...

This account reviews chelation-assisted carbonylation reactions catalyzed by late transition metals. New carbonylation reactions are achieved with these catalysts in the presence of pyridin-2-ylmethanol and pyridin-2-ylmethylamine. The reactions involve activation of O−H and N−H bonds, coordination of the pyridine nitrogen to Rh being essential for the reaction to proceed. In addition, a new ty...

Book: M. P. Doyle, M. A. McKervey, T. Ye Modern Catalytic Methods for Organic Synthesis with Diazo Compounds: From Cyclopropanes to Ylides; Wiley-VCH: New York, 1998. Comment: The authors propose an intriguing mechanistic pathways to explain the selectivity in the cyclopropanation with diazo reagents bearing two carboxy groups. It is proposed that the chiral rhodium complex preferentially binds...

Three lipocyclopeptides, aspartocins A (1), B (2), and C (3), were obtained from the aspartocin complex by reversed-phase HPLC separation. Their structures were elucidated by spectroscopic studies coupled with the previously published chemical degradation results. All three compounds, 1, 2, and 3, share the same cyclic decapeptide core of cyclo(Dab2-Pip3-MeAsp4-Asp5-Gly6-Asp7-Gly8-Dab9-Val10-Pr...

The title compound, [ZnCl(2)(C(10)H(12)N(4)O(2))]·0.5H(2)O, was readily prepared by the reaction between ZnCl(2) and 2-hydroxy-imino-N'-[1-(2-pyrid-yl)ethyl-idene]propanohydrazide. The Zn atom has a distorted trigonal-bipyramidal geometry with two Cl atoms and one azomethine N atom in the equatorial plane and one pyridine N atom and one amide O atom in the axial positions. In the crystal struct...

Amide and olefins are important synthetic intermediates with complementary reactivity which play a key role in the construction of natural products, pharmaceuticals and manmade materials. Converting the normally highly stable aliphatic amides into olefins directly is a challenging task. Here we show that a Ni/NHC-catalytic system has been established for decarbonylative elimination of aliphatic...

Orthogonal dipolar interactions between amide C=O bond dipoles are commonly found in crystal structures of small molecules, proteins, and protein-ligand complexes. We herein present the experimental quantification of such interactions by employing a model system based on a molecular torsion balance. Application of a thermodynamic double-mutant cycle allows for the determination of the increment...