Intermolecular reaction of internal alkynes and imines: propargyl tosylates as key partners in a gold-catalyzed [4 + 1] unusual cyclization leading to cyclopent-2-enimines.

Propargyl tosylates react with N-tosylaldimines to afford cyclopent-2-enimines in a gold-catalyzed process that involves a deep reorganization of both substrates. The formal [4 + 1] cyclization is initiated by a 1,2-migration of the tosylate that eventually generates a substituted 1,3-diene. Subsequent interaction with the imine launches a series of reaction steps prior to a Nazarov-like cyclization to yield the final product.

1,2-Diaryl(3-pyridyl)ethanone oximes. Intermolecular hydrogen bonding networks revealed by X-ray diffraction.

The synthesis of a set of 1-aryl-2-aryl(3-pyridyl)ethanones 1-5 and the corresponding ketoximes 6-9 is reported. Structural studies of oximes 6, 7 and 9 were performed in solution using (1)H-NMR and in the solid state by X-ray crystallography, providing evidence of H-bonding networks. The crystal packing was controlled by homomeric intermolecular oxime.

Effects of a novel disulfide bond and engineered electrostatic interactions on the thermostability of azurin.

Identification and evaluation of factors important for thermostability in proteins is a growing research field with many industrial applications. This study investigates the effects of introducing a novel disulfide bond and engineered electrostatic interactions with respect to the thermostability of holo azurin from Pseudomonas aeruginosa. Four mutants were selected on the basis of rational design and novel temperature-dependent atomic displacement factors from crystal data collected at elevated temperatures.

New Fischer carbene complexes of rhodium(i): preparation and 2-cyclopentenone ring synthesis by annelation to alkynes.

A new type of metal carbene complexes of group 9, specifically a cationic Fischer carbene of rhodium(I), has been synthesized from chromium carbene complexes via double transfer of carbene and CO ligands. These complexes reveal a different reactivity than other transition metal carbenes, including their chromium precursors, toward neutral and electron-poor alkynes, giving selectively polysubstituted cyclopentenones.

Combining image-seeking functions and a subtraction strategy: a vector-space procedure to improve many-body searches in molecular replacement.

Many-body searches in molecular replacement are usually carried out sequentially and each step benefits from the structural information obtained in previous rotational and translational stages. In this context, the incorporation of known structural information has proved to enhance the discrimination of a rotation function in Patterson space when many independent molecules have to be located in the asymmetric unit of the crystal cell. This improvement is achieved by subtraction of the contributions of already positioned molecules from the observed Patterson map, which makes the determination of the correct orientation of the remaining molecules easier.