The influence of lone-pair repulsions on C–C bond lengths: a critical evaluation of the experimental and theoretical evidence

X-Ray structural data, as well as semiempirical and ab initio molecular orbital calculations, reveal no systematic and substantial difference between the C–C bond lengths of cis and trans 1,2-diketones. Additional results on various conformations of 1,2-diimines and 1,2-dithiones follow the same pattern. Therefore, lone-pair repulsions cannot be implicated in the observed lengthening of C–C bonds in isatin and several related molecules. Conjugation in these systems occurs peripherally avoiding the participation of the central C–C bond. Negative hyperconjugative interaction between the oxygen lone pairs and the adjacent C–C σ* orbital is suggested to be the principal reason for the relatively long C–C bond in diketones. This effect is found in both the cis and trans conformations.

A new general method for the introduction of the aldehyde function in aromatic compounds

Side chain bromination of aromatic amidomethylated compounds yields aldehydes.

Crystal and Molecular Structure of N-acetyl-L-glutamine

The crystal and molecular structure of the title compound has been determined by direct methods from diffractometer data. Crystals are orthorhombic, with Z= 4 in a unit cell of dimensions : a= 13.811 (10), b= 5.095(5), c= 12.914(10)Å, space group P212121. The structure was refined by least-squares to R 3.31% for 868 observed reflections. There is significant non-planarity of the peptide group and its nitrogen atom is significantly pyramidal. There is no correlation between the double-bond character and reactivity of the C–N bond of the terminal amide group in glutamine and acetamide

Poly propyl ether imine (PETIM) dendrimer: A novel non-toxic dendrimer for sustained drug delivery

In the present study, an attempt was made to study the acute and sub-acute toxicity profile of G3-COOH Poly (propyl ether imine) PETIM] dendrimer and its use as a carrier for sustained delivery of model drug ketoprofen. Drug-dendrimer complex was prepared and characterized by FTIR, solubility and in vitro drug release study. PETIM dendrimer was found to have significantly less toxicity in A541 cells compared to Poly amido amine (PAMAM) dendrimer. Further, acute and 28 days sub-acute toxicity measurement in mice showed no mortality, hematological, biochemical or histopathological changes up to 80 mg/kg dose of PETIM dendrimer. The results of study demonstrated that G3-COOH PETIM dendrimer can be used as a safe and efficient vehicle for sustained drug delivery. (C) 2010 Elsevier Masson SAS. All rights reserved.

A self-assembled, luminescent europium cholate hydrogel: a novel approach towards lanthanide sensitization

We propose a new self-assembly based strategy for the design of novel lanthanide based luminescent materials. In this approach a europium hydrogel is prepared and sensitization is achieved by doping the gel with pyrene in a non-coordinated fashion.

Diterpenoids of Roylea calycina(Roxb.) Briq.

The structures of three new diterpenes, calyone, calyenone, and precalyone, isolated from the aerial portion of Roylea calycina have been shown to be 3-acetoxy-15,16-epoxy-9-hydroxylabda-1 3(16),14-dien-7-one (2), 3-acetoxy-15,16-epoxylabda-8,13(16),14-trien-7-one (5), and 3-acetoxy-9,13;15,16-diepoxylabda-14-en-7-one (7), respectively, by chemical and spectroscopic studies. Precalyone showed antitumor activity against P-388 lymphocytic leukaemia.