Links between the Slater Index and the Ryser Index of Tournaments

Given a tournament T, the Slater index i(T) of T is the minimum number of arcs that must be reversed to make T transitive. The Ryser index (T) of T, defined from the out-degrees of T, measures a remoteness between T and the transitive tournaments of same order. In this paper, we study some links between i(T) and (T). More precisely, calling I(n, ) the maximum value of i(T) over the set of tournaments on n vertices and such that (T)=, we compute an upper bound of I(n,) for every value of . Then we use this upper bound to study a conjecture stated by J.-C. Bermond on the regularity (i.e., the fact that all the out-degrees are equal or almost equal) of the tournaments with a maximum Slater index by showing that the out-degrees of such tournaments cannot be too far from the ones of the regular tournaments.     

Constructing complete tables of quartic fields using Kummer theory

We explain how to construct tables of quartic fields of discriminant less than or equal to a given bound in an efficient manner using Kummer theory, instead of the traditional (and much less efficient) method using the geometry of numbers. As an application, we describe the computation of quartic fields of discriminant up to , the corresponding table being available by anonymous ftp.     

β-Cyano meso-unsubstituted porphyrins for intramolecular charge transfer

β-Cyano meso-unsubstituted porphyrin 10, synthesized via a ‘3+1’ condensation using a bromotripyrrane, shows an effective charge transfer interaction across the porphyrin between electron-acceptor and -donor groups in β-positions.     

Reductive decomplexation of pi-allyltricarbonyliron lactone complexes using sodium naphthalenide as a route to stereodefined 1,7-diols and 2,3-diene-1,7-diols

Treatment of pi-allyltricarbonyliron lactone complexes, that contain an adjacent leaving group, with lithium naphthalenide causes decomplexation to acyclic dienols in excellent yield and without any stereochemical scrambling of the allylic centre. When an endo complex is employed (E,E)-geometry prevails with good selectivity whereas (Z,E)-geometry dominates in the case of exo complexes. A mechanism consistent with the observed stereo- and regiochemistry is proposed.     

Fully automated multi-step solution phase synthesis using polymer supported reagents: preparation of histone deacetylase inhibitors

The first fully automated multi-step polymer assisted solution phase (PASP) synthesis is described. An array of histone deacetylase (HDAc) inhibitors was prepared by an unattended 4-5 step sequence incorporating in-line 'catch and release' purification.     

Iterative oxime bond chemistry leads to protease inhibitors

[structure: see text] In the present paper, we have looked at iterative coupling as a strategy to form new druglike molecules. We have developed an iterative coupling chemistry based on oxime bond formation between hydroxyaromatic aldehyde building blocks to form linear oxime oligomers. The strategy is validated by the discovery of micromolar protease inhibitors.     

Total synthesis of the reputed structure of alcyonin and reassignment of its structure

Introduction of the C4 hydroxyl group by an epoxy ester rearrangement is a pivotal step in the first total synthesis of the purported structure of alcyonin. As the spectral data for diol acetate 3 do not match those reported for alcyonin, the structure of this marine diterpene must be revised. Reexamination of NMR spectra, MS data, and chemical transformations of natural alcyonin suggests that the structure of this marine metabolite is allylic peroxide 15.[structure: see text]     

Rational improvement of centrifugal partition chromatographic settings for the production of 5-n-alkylresorcinols from wheat bran lipid extract. I. Flooding conditions--optimizing the injection step

A dedicated CPC prototype permits direct flow pattern visualization in the partition cells of a CPC column. It was used to understand "flooding", a frequent phenomenon associated with large injections. A general strategy was developed to optimize the injection step in the framework of a particular preparative separation: the purification of 5-n-alkylresorcinols from a wheat bran lipid extract on a several hundred milligram scale. The construction of the "mobile phase/stationary phase/sample" pseudo ternary diagram characterizes the effect of the injected solution on mobile and stationary phases. The position of the binodal curve maximum indicates if the biphasic system is "robust" towards a large injection or not, and can be used for optimum mass load determination.     

Influence of the correlation,aggregation, and solvation on ab initio computed Li-C,Li-N,and Li-Li NMR coupling constants

The (1)J and (3)J(C-Li), (1)J(N-Li), and (2)J(Li-Li) NMR coupling constants have been calculated for various homogeneous and heterogeneous aggregates of methyllithium and lithium dimethylamide at the HF and MP2 levels of calculation. Ethereal solvation has also been taken into account either through a continuum model or through the explicit introduction of Me(2)O molecules. The results obtained are in good general agreement with the experimental data available for methyllithium itself or model alkyllithiums and supports the empirical rule proposed by Bauer, Winchester, and Schleyer to evaluate (1)J(C-Li) provided that calculations include solvent and/or aggregation effects.