Sur l'acylation des méthylfluorènes III [1]: Benzoylation et acétylation du méthyl-3-fluorène

Benzoylation and acétylation of 3-methyl-fluorene according to Friedel-Crafts in carbon disulfide with aluminium chloride yielded the corresponding 2-acyl derivatives. By oxidation the benzoyl derivative gave 2-benzoyl-9-oxo-fluorene-3-carboxylic acid, cychsable into the known 2,3-phthalyl-fluorenone. By Clemmensen reduction, the acetyl derivative gave 3-methyl-2-ethyl-fluorene.     

Sur les dérivés de la fluorénone. IX. La (pyridyl-2)-3-fluorénone,la méthyl-2-(pyridyl-2)-3-fluorénone et la méthyl-3-(pyridyl-2)-3-fluorénone

Fluorenone Derivatives. IX. 3-(Pyrid-2-yl)-fluorenone, 2-methyl-3-(pyrid-2-yl)-fluorenone, and 2-(3-methyl-pyrid-2-yl)fluorenone Unsuccessful attempts to synthesize an aza-cis-fluorenacene system starting from 2-aza-chalcone or 6-methyl-2-aza-chalcone led to the title compounds.     

Chemistry of the phenoxathiins. III. Synthesis of benzo[1″,2″:5,6:5″,4″:5′,6′]bis[1,4]oxathiino[3,2-b:3′,2′-b']dipyridine

As a result of studies dealing with the synthesis of 1-azaphenoxathiins, the synthesis of benzo[1″,2″:5,6:5″,4″:5′,6′]bis[1,4]oxathiino[3,2-b:3′,2′-b']dipyridine was examined. Unique evidence of solvent participation in the synthesis of these compounds by the structure elucidation of a novel minor by-product formed during the synthesis of the title compound is also reported.     

Vacancy at the Si(111) unreconstructed surface: Electron states and absence of the Jahn-Teller distortion

The electron states of a vacancy at the Si(111) surface are calculated by means of a tight-binding scheme. The results for a vacancy at the surface layer show one state of A_l symmetry below the surface dangling bond band, and another doubly degenerate state of E symmetry above it. The Fermi energy at an isolated vacancy remains fixed by the surface. This allows to derive two important consequences: i) The vacancy state is a neutral one as can be shown by integrating the local density of states up to the Fermi energy. ii) The electronic charge around the vacancy has got the whole surface point symmetry and therefore a Jahn-Teller effect is not induced.     

Re-entrant phase behavior for systems with competition between phase separation and self-assembly

In patchy particle systems where there is a competition between the self-assembly of finite clusters and liquid-vapor phase separation, re-entrant phase behavior can be observed, with the system passing from a monomeric vapor phase to a region of liquid-vapor phase coexistence and then to a vapor phase of clusters as the temperature is decreased at constant density. Here, we present a classical statistical mechanical approach to the determination of the complete phase diagram of such a system. We model the system as a van der Waals fluid, but one where the monomers can assemble into monodisperse clusters that have no attractive interactions with any of the other species. The resulting phase diagrams show a clear region of re-entrance. However, for the most physically reasonable parameter values of the model, this behavior is restricted to a certain range of density, with phase separation still persisting at high densities.     

A combinatorial approach toward the generation of ambiphilic peptide-based inhibitors of protein:geranylgeranyl transferase-1

A combinatorial synthesis of oligopeptide analogues and their evaluation as protein:geranylgeranyl transferase inhibitors is presented. The combinatorial strategy is based on the random mutation, in each new generation, of one of any of the four amino acid building blocks of which the most effective compounds of the previous generation are assembled. In this way, a progressive improvement of the average inhibitory activity was observed until the fifth generation. The most active inhibitors were found to inhibit PGGT-1 in the low micromolar range (IC(50): 3.8-8.1 microM).     

STEREOCHEMICAL PROPERTIES OF THE 1-CHLORO-1- PHENYL-2,5-DIMETHYL-2-PHOSPHOLENIUM ION AND DERIVED OXIDE AND PHOSPHINE

Abstract

The cycloaddition of phenylphosphonous dichloride and trans, trans-2,4-hexadiene, or the addition of chlorine to trans-1-phenyl-cis-2,5-dimethyl-3-phospholene, gave 1-chloro-1-phenyl-2,5-dimethyl-2-phospholenium chloride. This compound shows no evidence in its ³¹P and ¹H nmr spectra for the existence of cis, trans isomers, yet on hydrolysis or dehalogenation with magnesium the resulting oxide and phosphine, respectively, are seen to be isomer mixtures. This phenomenon is explained by a rapid equilibration of the cis, trans form of the I-chloro ion through a pentacovalent species. Structures of the oxides and phosphines were assigned by ¹H and ¹³C nmr relations. The 1-phenyl-cis-2,5-dimethyl-3-phospholenium ion and related compounds were also characterized.