A method is presented that positions polar hydrogen atoms in protein structures by optimizing the total hydrogen bond energy. For this goal, an empirical hydrogen bond force field was derived from small molecule crystal structures. Bifurcated hydrogen bonds are taken into account. The procedure also predicts ionization states of His, Asp, and Glu residues. During optimization, side-chain confor...

3-Aminomethylation of salicylalkylamides afforded hybrids with a Mannich base. In addition, it triggered the rotation of the amide bond. The observed conformational switch is driven by strong intramolecular hydrogen bonding between the Mannich base and phenolic group. Crystal structure analysis reveals the stabilization of the hybrid molecules by double hydrogen bonding of the phenolic OH, whic...

In the title compound, C12H8Cl2N2O4S, the N-C bond in the C-SO2-NH-C segment has gauche torsions with respect to the S=O bonds. Further, the N-H bond is syn to the ortho-nitro group in the sulfonyl benzene ring and also syn to both the ortho- and meta-Cl atoms in the aniline ring. The mol-ecule is twisted at the S-N bond with a torsion angle of 61.15 (18)°. The dihedral angle between the planes...

have been structurally characterized, relatively few free Schiff bases have been similarly characterized.1 N-Substituted salicylaldimines show photochromism and thermochromism in the solid state. These effects are produced by intramolecular proton transfer associated with a change in the π-electron configuration.2 As part of a general study of tetradentate Schiff bases, we determined the struct...

In the title compound, C25H20N6O2·0.15H2O, the dihedral angles between the least-squares planes of the indole and pyrrolidine rings and between the oxindole and imidazole rings are 77.66 (7) and 45.31 (7)°, respectively. The pyrrolidine ring and the fused five-membered pyrrolidine ring of the oxindole moiety exhibit twisted conformations. The amide N atom is involved in both intra- and inter-mo...

The reliability of four force fields developed for 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids are compared to an ab inito molecular dynamics simulation regarding structural properties. Except the hydrogen bond structure between the most acidic hydrogen atom of the imidazolium ring and the nitrogen atom of the anion as well as the intramolecular potential surface...

In the title compound, C(14)H(12)ClNO(3)S·H(2)O, the dihedral angle between the sulfonyl and benzoyl benzene rings is 84.4 (2)°. In the crystal, every water mol-ecule forms four hydrogen bonds with three different mol-ecules of 4-chloro-N-(3-methyl-benzo-yl)benzene-sulfonamide. One of the water H atoms forms a bifurcated hydrogen bond with both the sulfonyl and the carbonyl O atoms of the same ...

In the title compound, C(13)H(10)N(2)O(5)S·H(2)O, the dihedral angle between the sulfonyl and benzoyl benzene rings is 83.4 (1)°. In the crystal, the water mol-ecule forms four hydrogen bonds with three different mol-ecules of N-benzoyl-4-nitro-benzene-sulfonamide. One of the H atoms of H(2)O forms a bifurcated hydrogen bond with a sulfonyl and the carbonyl O atoms. Mol-ecules are linked into a...

The title compound, C20H26O6, is chiral and crystallizes as a racemate: the relative configuration of the stereogenic centres is 1R*,2R*,3S*,4R*. The cyclo-hexane ring has a chair conformation. The ethyl fragment of the eth-oxy-carbonyl group in the 3-position is disordered over two sets of sites in a 0.650 (6):0.350 (6) ratio. The hy-droxy group acts as a bifurcated hydrogen-bond donor, formin...