Based on the local Shannon entropy concept in information theory, a new measure of aromaticity is introduced. This index, which describes the probability of electronic charge distribution between atoms in a given ring, is called Shannon aromaticity (SA). Using B3LYP method and different basis sets (6-31G**, 6-31+G** and 6-311++G**), the SA values of some five-membered heterocycles, C(4)H(4)X, a...

A new formulation of a pose refinement technique using “active” models is described. An error term derived from the detection of image derivatives close to an initial object hypothesis is linearised and solved by least squares. The method is particularly well suited to problems involving external geometrical constraints (such as the ground-plane constraint). We show that the method is able to r...

Four fundamental physical parameters of series of benzene derivatives were studied to ascertain correlations with biological activity. These included octanol/water coefficient, vapor pressure, infrared absorption (out-of-plane C-H vibration), and the pi values. Each physicochemical constant exhibited a partial correlation with biological activity suggesting that each played a role. It was presu...

Psammaplin F, an unsymmetrical disulfide bromotyrosine, was isolated from the sponge Pseudoceratina purpurea in 2003. We reported here the first total synthesis of psammaplin F in 12% overall yield by employing Cleland's reagent reduction as key step. The longest linear synthetic sequence starting from 3-bromo-4-hydroxybenzaldehyde and hydantoin was seven steps. In addition, a detailed X-ray cr...

Acid-catalysed, '3+3' condensation of m-bispyrryl benzene derivatives with acetone afforded new non-aromatic macrocycles that can be converted to meso-alkylidenyl dibenzohexaphyrins carrying four exocyclic double bonds at meso-positions by DDQ oxidation.

2-(Alkyl-1-yl)-1H-imidazol-5(4H)-ones 5a-n were synthesized via nucleophilic substitution of the methylsulfanyl group of the corresponding 2-(methylthio)-1H-imidazol-5(4H)-ones 3a-c with suitably substituted secondary amines. The starting 2-thioxo- imidazolidin-4-ones 2a,2b were prepared by condensation of thiohydantoin and benzo[b]-thiophene-3-carbaldehyde or benzofuran-3-carbaldehyde under mi...

The methylation and oxidative demethylation of cytosine in CpG dinucleotides plays a critical role in the regulation of genes during cell differentiation, embryogenesis and carcinogenesis. Despite its low abundance, 5-methylcytosine (5mC) is a hotspot for mutations in mammalian cells. Here, we measured five oxidation products of 5mC together with the analogous products of cytosine and thymine i...

G-quadruplex is a four-stranded G-rich DNA structure that is highly susceptible to oxidation. Despite the important roles that G-quadruplexes play in telomere biology and gene transcription, neither the impact of guanine lesions on the stability of quadruplexes nor their repair are well understood. Here, we show that the oxidized guanine lesions 8-oxo-7,8-dihydroguanine (8-oxoG), guanidinohydan...