Synthesis and conformation of fluorinated ß-peptidic compounds.

Experimental and theoretical data indicate that, for α-fluoroamides, the F-C-C(O)-N(H) moiety adopts an antiperiplanar conformation. In addition, a gauche conformation is favoured between the vicinal C-F and C-N(CO) bonds in N-ß-fluoroethylamides. This study details the synthesis of a series of fluorinated ß-peptides (1-8) designed to use these stereoelectronic effects to control the conformation of ß-peptide bonds. X-ray crystal structures of these compounds revealed the expected conformations: with fluorine ß to a nitrogen adopting a gauche conformation, and fluorine α to a C=O group adopting an antiperiplanar conformation. Thus, the strategic placement of fluorine can control the conformation of a ß-peptide bond, with the possibility of directing the secondary structures of ß-peptides.

Crystal structure and magnetism of a well isolated 2D-quantum Heisenberg antiferromagnet, (Quinolinium)(2)CuBr(4).2H(2)O, and its anhydrous form.

Reaction of quinoline with HBr and CuBr(2) generates a mixture of two compounds, (quinolinium)(2)CuBr(4).2H(2)O (1) and (quinolinium)(2)CuBr(4) (2) for which single-crystal X-ray structures have been solved. Compound 1 crystallizes in the monoclinic space group C2/c as layers of tetrabromocuprate ions which are separated by intervening layers of quinolinium ions. Compound 2 crystallizes in the triclinic space group P1. Magnetic data analysis reveals that 1 behaves as a 2D-quantum Heisenberg antiferromagnet with 2J/k(B) = -6.17(3) K within the layers. High field magnetization data at low temperatures suggests that T(N) must be less than 1.8 K for 1, yielding a figure of merit |k(B)T(N)/2J| < 0.29, which indicates excellent isolation between the layers. Magnetic exchange in compound 2 was much weaker and was fit to a linear chain antiferromagnet with 2J/k(B) = -1.59(3) K.

Bis(pyridine-κN){N,N-[1,1'-(pyridine-2,6-di-yl)diethyl-idyne]benzene-sulfono-hydrazonato-κO,N,N',N'',O'}nickel(II).

In the crystal structure of the title compound, [Ni(C(21)H(19)N(5)O(4)S(2))(C(5)H(5)N)(2)], the metal center is seven-coordinate, with an approximate penta-gonal-bipyramidal configuration. The Ni atom is chelated by a dianionic penta-dentate Schiff base via the pyridine N atom, the two azomethine N atoms and the two sulfonyl O atoms. The latter coordinate to Ni at different distances, viz. 2.3337 (12) and 2.7988 (12) Å. Two apically coordinated pyridine mol-ecules complete the seven-coordin-ate geometry. The dihedral angle between the two pyridine ring planes is 68.25 (6)°.

N'-[1-(5-Bromo-2-hydroxy-phen-yl)ethyl-idene]-3,4,5-trihydroxy-benzohydrazide dimethyl sulfoxide solvate trihydrate.

The benzohydrazide mol-ecule in the title compound, C(15)H(13)BrN(2)O(5)·C(2)H(6)OS·3H(2)O, is almost planar with an r.m.s. deviation for the non-H atoms of 0.078 Å. The organic mol-ecules, water and dimethyl sulfoxide solvent mol-ecules are linked by N-H⋯O, O-H⋯O and O-H⋯S inter-molecular hydrogen bonds, forming zigzag chains along the a axis. Intra-molecular O-H⋯O and O-H⋯N hydrogen bonds also occur.

2-(Benzo[d]thia-zol-2-ylsulfon-yl)-1-(4-bromo-phen-yl)ethanone.

In the title mol-ecule, C(15)H(10)BrNO(3)S(2), the dihedral angle between the benzothia-zole ring system and the benzene ring is 67.57 (12)°. The crystal structure is stabilized by weak inter-molecular C-H⋯O inter-actions. In addition, there is an inter-molecular Br⋯C [3.379 (3) Å] contact which is shorter than the sum of the van der Waals radii of these atoms.

Bis[4-(dimethyl-amino)pyridinium] tetra-bromidobis(4-chloro-phen-yl)stannate(IV)-4-bromo-chloro-benzene (1/1).

In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(6)H(4)Cl)(2)]·C(6)H(4)BrCl, the Sn(IV) atom in the tetra-bromidobis(4-chloro-phen-yl)stannate(IV) anion lies on a centre of inversion. The distances between the 4-(dimethyl-amino)pyridinium N atom and the Br atoms of the anion are 3.450 (2) and 3.452 (2) Å, suggesting weak hydrogen bonding. The 4-bromo-chloro-benzene solvent mol-ecule, which is a bromination by-product from the reaction, is disordered about a twofold rotation axis with approximately equal occupancy.

Bis[4-(dimethyl-amino)pyridinium] tetra-bromidobis(4-methyl-phen-yl)stannate(IV).

In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(7)H(7))(2)], the tetra-bromidobis(4-methyl-phen-yl)stannate(IV) anion possesses a centre of inversion located at the Sn(IV) atom. In the crystal structure, two inversion-related cations are linked to the anion via weak N-H⋯Br hydrogen bonds.

2-(1,3-Benzoxazol-2-ylsulfan-yl)-1-phenyl-ethanone.

In the title compound, C(15)H(11)NO(2)S, a new thio-benzoxazole derivative, the dihedral angle between the benzoxazole ring and the phenyl ring is 9.91 (9)°. An inter-esting feature of the crystal structure is the short C⋯S [3.4858 (17) Å] contact, which is shorter than the sum of the van der Waals radii of these atoms. In the crystal structure, mol-ecules are linked together by zigzag inter-molecular C-H⋯N inter-actions into a column along the a axis. The crystal structure is further stabilized by inter-molecular π-π inter-actions [centroid-centroid = 3.8048 (10) Å].

2-(1,3-Benzothia-zol-2-ylsulfan-yl)-1-phenyl-ethanone.

In the mol-ecule of the title compound, C(15)H(11)NOS(2), the 1,3-benzothia-zole ring is oriented at a dihedral angle of 6.61 (6)° with respect to the phenyl ring. In the crystal structure, inter-molecular C-H⋯O inter-actions link the mol-ecules in a herring-bone arrangement along the b axis and π-π contacts between the thia-zole and phenyl rings [centroid-centroid distance = 3.851 (1) Å] may further stabilize the structure.

(E)-3-(6-Nitro-benzo[d][1,3]dioxol-5-yl)-1-(2,4,6-trimethoxy-phen-yl)prop-2-en-1-one.

In the mol-ecule of the title compound, C(19)H(17)NO(8), the benzodioxole unit is oriented at a dihedral angle of 61.45 (6)° with respect to the meth-oxy-substituted phenyl ring. The nitro group is not co-planar to the benzene ring to which it is attached, making a dihedral angle of 31.86 (17)°. In the crystal structure, inter-molecular C-H⋯O inter-actions link the mol-ecules into chains through R(2) (2)(8) ring motifs. The π⋯π contacts between the benzodioxole rings, [centroid-centroid distances = 3.7610 (9), 3.6613 (9) and 3.7975 (9) Å] may further stabilize the structure.

A second monoclinic polymorph of 2-(diformyl-methyl-idene)-3,3-dimethyl-2,3-dihydro-1H-indole.

The crystal structure of the title compound, C(13)H(13)NO(2), is a polymorph of the structure first reported by Helliwell et al. [Acta Cryst. (2006), E62, o737-o738]. It is also monoclinic (space group P2(1)/c), but with completely different cell constants. The mol-ecular conformations of these polymorphs differ by a 180° rotation of one formyl group. The present mol-ecule is planar [maximum deviation 0.089 (2) Å] with the exception of the two methyl groups which lie on either side of the plane. There are strong intra- and inter-molecular N-H⋯O hydrogen bonds. The latter link pairs of mol-ecules across crystallographic centers of symmetry. Two aldehyde O atoms are brought close together [2.896 (4) Šin this arrangement but are not hydrogen bonded. In the earlier polymorph, one formyl group is rotated by 180° to yield inter-molecular hydrogen bonding and an infinite polymeric chain. The other formyl group is involved in the same intra-molecular hydrogen bonding as has been found here.

3,4,5-Trihydr-oxy-N'-(1H-indol-2-ylmethyl-idene)benzohydrazide-1H-indole-2-carbaldehyde azine-methanol (2/1/2).

The title compound, 2C(16)H(13)N(3)O(4)·C(18)H(14)N(4)·2CH(4)O, was crystallized from the reaction between 3,4,5-trihydroxy-benzoyl-hydrazine and indole-2-carbaldehyde in a mixture of ethanol and methanol. The compound is a stoichiometric 2:1 cocrystal of the methanol-solvated reaction product, 3,4,5-trihydr-oxy-N'-(1H-indol-2-ylmethyl-idene)benzohydrazide and 1H-indole-2-carbaldehyde azine that arose unexpectedly during the synthesis. The former mol-ecules are linked by O-H⋯O hydrogen bonds and also by π-π stacking inter-actions between benzoyl-hydrazide rings into a two-dimensional network. The methanol solvent mol-ecules are hydrogen bonded to this network. The centrosymmetric azine mol-ecules are not engaged in hydrogen bonding.

catena-Poly[[triphenyl-tin(IV)]-µ-2-[(3,5-di-tert-butyl-4-hydroxy-benz-yl)sulfan-yl]acetato-κO:O'].

The title compound, [Sn(C(6)H(5))(3)(C(17)H(25)O(3)S)](n), comprises two symmetry-independent five-coordinated triphenyl-tin mol-ecules which are linked by carboxyl-ate bridges into a polymeric chain. The Sn(IV) atom is in a distorted trans-C(3)SnO(2) trigonal-bipyramidal geometry. The presence of two bulky tert-butyl groups on the benzene ring prevents any hydrogen-bonding inter-actions involving the hydroxyl substituents.

3,4,5-Trihydr-oxy-N'-[(1-methyl-1H-indol-2-yl)methyl-idene]benzohydrazide.

The structure of the title compound, C(17)H(15)N(3)O(4), displays inter-molecular O-H⋯N and O-H⋯O hydrogen bonding between adjacent mol-ecules. Intra-molecular O-H⋯O hydrogen bonds also occur. The molecule is essentially planar with a deviation of 0.090 (1) Šfrom the best plane running through the connected ring systems.

N'-(2,4-Dimethoxy-benzyl-idene)-3,4,5-trihydroxy-benzohydrazide ethanol solvate.

The title compound, C(16)H(16)N(2)O(6)·C(2)H(5)OH, was synthesized from 3,4,5-trihydroxy-benzoyl-hydrazide and 2,4-dimethoxy-benzaldehyde in ethanol. The compound is not planar, with the two aromatic planes of the two aromatic rings twisted by 15.6 (1)°. The hydr-oxy groups are involved in both intra-molecular O-H⋯O and inter-molecular O-H⋯N and O-H⋯O hydrogen bonds and a C-H⋯O interaction also occurs.

N-[1-(2-Hydroxy-phen-yl)ethyl-idene]-N-(1H-indol-3-ylmethyl-ene)carbonic dihydrazide.

In the crystal structure of the title compound {alternative name: 1-[1-(2-hydroxy-phen-yl)ethyl-ideneamino]-3-(1H-indol-3-ylmethyl-eneamino)urea}, C(18)H(17)N(5)O(2), the planar indole component is twisted at an angle of 63.7 (10)° with respect to the rest of the mol-ecule. This compound is one of a series being studied for biological activity. The hydr-oxy groups are involved in both intra-molecular (O-H⋯N) and inter-molecular (N-H⋯O) hydrogen bonds.

2-{3-Cyano-5,5-dimethyl-4-[4-(pyrrol-idin-1-yl)buta-1,3-dien-yl]-2,5-dihydro-furan-2-yl-idene}malononitrile dichloro-methane solvate.

The structure of the title compound, C(18)H(18)N(4)O·CH(2)Cl(2), was solved using data collected from a multiple crystal (note high R factors). The crystal structure is dominated by two bifurcated attractive C-H⋯N(cyano) inter-actions.

N'-[1-(2-Hydr-oxy-5-methyl-phen-yl)ethyl-idene]benzene-sulfonohydrazide.

The two independent mol-ecules in the asymmetric unit of the title compound, C(15)H(16)N(2)O(3)S, are each linked by an N-H⋯O(sulfon-yl) hydrogen bond into a linear chain that runs along the shortest axis of the triclinic unit cell. The hydr-oxy groups are engaged in intra-molecular hydrogen bonding and the amino N atom shows pyramidal coordination.

N'-(2-Hydr-oxy-5-nitro-benzyl-idene)-2-(1H-indol-3-yl)acetohydrazide.

The mol-ecule of the title compound, C(17)H(14)N(4)O(4), uses its amide -NH- group to form a hydrogen bond to the amido -C(=O)- group of an adjacent mol-ecule to furnish a linear chain structure. The hydr-oxy group forms an intra-molecular hydrogen bond; the indolyl -NH- unit does not engage in any strong hydrogen-bonding inter-actions.

Bis{2-bromo-4-chloro-6-[2-(phenyl-sulfon-yl)hydrazonometh-yl]phenolato-κN,O}copper(II).

The Cu atom in the title compound, [Cu(C(13)H(9)BrClN(2)O(3)S)(2)], is chelated by two deprotonated Schiff base ligands in a square-planar coordination geometry; the Cu atom lies on a center of inversion. The -NH- group of one anion forms an intra-molecular hydrogen bond to the phenolate atom of the symmetry-related ion.