Synthesis and structure of [(nitrito-O,O′) bis(di-2-pyridylamine)copper(II)] nitrite

The synthesis and molecular structure of the title compound, [(nitrito-O,O) (dpa)₂Cu(II)] (NO₂), 1, is reported. Compound 1 crystallized in the orthorhombic space group Pccn with a = 11.397(5) Å, b = 12.256(6) Å, c = 14.876(8) Å, and V = 2077.9(17) ų with Z = 4. The distorted octahedral copper(II) cations are linked through a hydrogen-bonded polymer network. The polymer network is formed through the amine N–H of the cations and hydrogen bonded to the N–HO nitrite anions.     

Synthesis of an unusual, cage-functionalized molecular cleft

The synthesis and X-ray crystal structure of a novel, cage-functionalized bis(-diketone), 4, is described. A molecular cleft is formed by two parallel planar aromatic diketone units bridged by a polycarbocyclic cage. Crystal data: T = 100(1) K, monoclinic, C2/c, a = 35.6383(2), b = 11.8110(1), c = 15.6319(2) Å, = 110.7745(2)°, V = 6152.04(9) ų, Z = 12, R = 0.0691. Compound 4 is of potential interest as a new type of host molecule for the study of host–guest interactions in solution.     

Synthesis of the seco-Limonoid BCD Ring System Identifies a Hsp90 Chaperon Machinery (p23) Inhibitor

D-Ring-seco-limonoids (tetranortriterpenoids), such as gedunin and xylogranin B display anti-cancer activity, acting via inhibition of Hsp90 and/or associated chaperon machinery (e.g., p23). Despite this, these natural products have received relatively little attention, both in terms of an enabling synthetic approach (which would allow access to derivatives), and as a consequence their structure–activity relationship (SAR). Disclosed herein is a generally applicable synthetic route to the BCD ring system of the seco-D-ring double bond containing limonoids. Furthermore, cell based assays revealed the first skeletal fragment that exhibited inhibition of the p23 enzyme at a level which was equipotent to that of gedunin, despite being much less structurally complex.     

Photoelectron Spectra of Azabenzenes and Azanaphthalenes: III. The orbital sequence in methyl- and trimethylsilyl-substituted pyridines

The ionization potentials of methyl-, t-butyl- and trimethylsilyl-substituted pyridines have been determined by high-resolution photoelectron spectroscopy. The results are discussed in terms of destabilizing inductive and stabilizing conjugative effects of the substituents, and have been parametrized on the basis of a HMO-type perturbation treatment. Our data are in accord with the idea that the topmost occupied orbital in pyridine is a ‘lone pair’ orbital.     

Production of "internal surface reversed-phase" supports: the hydrolysis of selected substrates from silica using chymotrypsin

The degree of hydrolysis of substrates attached to silica supports with alpha-chymotrypsin has been evaluated relative to the production of "internal surface reversed-phase" supports. The peptide substrates N-tert.-butoxycarbonyl-L-phenylalanine (Boc-L-Phe), N-carbobenzoxy-L-valine-L-phenylalanine, N-acetyl-L-phenylalanine (acetyl-L-Phe) and N-benzoyl-L-phenylalanine as well as phenylpropionic acid were attached to glycerylpropyl-bonded silica via a diamine spacer using 1,1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as a coupling catalyst. The products released from the silica support on enzyme treatment were quantified by high-performance liquid chromatography. Boc-L-Phe and acetyl-L-Phe were successfully cleaved from the rigid silica matrix in high yields, whereas the remaining substrates were hydrolyzed to a lesser extent.     

Aryl aldehydes as traceless dielectrophiles in bifunctional titanocene-catalyzed propargylic C-X activations

The titanocene-catalyzed construction of all-carbon substituted tertiary centers directly from aromatic aldehydes is described. The starting aldehyde behaves as a traceless functionality in the formation of multiple carbon-carbon bonds through consecutive carbon-heteroatom bond activations. The sequential addition of a metal acetylide and a second carbon nucleophile to the dielectrophilic aldehyde enables the construction of symmetrical and unsymmetrical 1,4-diynes in good yields.