Synthesis and crystal structure of peptide dimethyl biphenyl hybrid C52H60N6O10·0.25H2O

The synthesis and crystal structure of peptide 6,6′-dimethyl biphenyl hybrid are described. The title compound was synthesized by reaction between 6,6′-dimethyl-[1,1′-biphenyl]-2,2′-dicarbonyl dichloride in CH2Cl2, amine HN–proline–phenylalanine–alanine–COOMe and Et3N at 273 K under N2 atmosphere and characterized by single-crystal X-ray diffraction. The asymmetric unit contains one peptide molecule and a quarter of a water molecule. A disorder of a methyl and methoxycarbonyl group of one alanine residue is observed with occupancy ratio 0.502 (6):0.498 (6). The structure is consolidated by intra- and intermolecular hydrogen bonds.

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

Starting from γ-ketoesters with an o-iodobenzyl group we studied a palladium-catalyzed cyclization process that stereoselectively led to bi- and tricyclic compounds in moderate to excellent yields. Four X-ray crystal structure analyses unequivocally defined the structure of crucial cyclization products. The relative configuration of the precursor compounds is essentially transferred to that of the products and the formed hydroxy group in the newly generated cyclohexane ring is consistently in trans-arrangement with respect to the methoxycarbonyl group. A transition-state model is proposed to explain the observed stereochemical outcome. This palladium-catalyzed Barbier-type reaction requires a reduction of palladium(II) back to palladium(0) which is apparently achieved by the present triethylamine.

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

A synthesis of new NeoPHOX ligands derived from serine or threonine has been developed. The central intermediate is a NeoPHOX derivative bearing a methoxycarbonyl group at the stereogenic center next to the oxazoline N atom. The addition of methylmagnesium chloride leads to a tertiary alcohol, which can be acylated or silylated to produce NeoPHOX ligands with different sterical demand. The new NeoPHOX ligands were tested in the iridium-catalyzed asymmetric hydrogenation and palladium-catalyzed allylic substitution. In both reactions high enantioselectivities were achieved, that were comparable to the enantioselectivities obtained with the up to now best NeoPHOX ligand derived from expensive tert-leucine.

Fmoc–RGDS based fibrils: atomistic details of their hierarchical assembly

We describe the 3D supramolecular structure of Fmoc–RGDS fibrils, where Fmoc and RGDS refer to the hydrophobic N-(fluorenyl-9-methoxycarbonyl) group and the hydrophilic Arg-Gly-Asp-Ser peptide sequence, respectively.

Crystal structure of 4-(methoxycarbonyl)phenylboronic acid

In the title compound, C8H9BO4, the methoxycarbonyl group is rotated out of the plane of the benzene ring by 7.70 (6)°. In the crystal, molecules are linkedviapairs of O—H...O hydrogen bonds, involving the boronic acid OH groups, forming inversion dimers. The dimers are linkedviaO—H...O hydrogen bonds, involving a boronic acid OH group and the carbonyl O atom, forming undulating sheets parallel to (10-2). Within the sheets there are also C—H...O hydrogen bonds present, also involving the carbonyl O atom. The sheets are linkedviaC—H...π and offset face-to-face π-interactions between inversion-related molecules [inter-centroid distance = 3.7843 (16) Å, interplanar distance = 3.3427 (4) Å and offset = 1.744 Å], forming a three-dimensional structure.

Synthesis, Photophysical Properties and Photoinduced Intermolecular Electron Transfer of a Novel Aryl Benzyl Ester Dendritic Axially Substituted Silicon (IV) Phthalocyanine

An aryl benzyl ester dendritic axially substituted silicon (IV) phthalocyanine, a di-{3,5-di-(4-methoxycarbonyl group benzyloxy) benzyloxy) benzyloxy} axially substituted silicon (IV) phthalocyanine (DSiPc) was synthesized. Its structure was characterized by elemental analysis, 1H NMR, IR and ESI-MS. The photophysical property of DSiPc was studied by steady and time-resolved spectroscopic methods. The steric hindrance of dendritic structure can reduced the aggregation efficiently. The photoinduced intermolecular electron transfer between this novel macromolecule and benzoquinone was studied. The results showed that the fluorescence emission of this dendritic phthalocyanine could be quenched by BQ. Therefore, this novel dendritic phthalocyanine was an effective new electron donor and transmission complex could be used as a potential artificial photosynthesis system.