Didier Villemin

Support vector machines: development of QSAR models for predicting anti-HIV-1 activity of TIBO derivatives.

The tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepinone (TIBO) derivatives, as non-nucleoside reverse transcriptase inhibitors, acquire a significant place in the treatment of the infections by the HIV. In the present paper, the support vector machines (SVM) are used to develop quantitative relationships between the anti-HIV activity and four molecular descriptors of 82 TIBO derivatives. The results obtained by SVM give good statistical results compared to those given by multiple linear regressions and artificial neural networks. The contribution of each descriptor to structure-activity relationships was evaluated. It indicates the importance of the hydrophobic parameter. The proposed method can be successfully used to predict the anti-HIV of TIBO derivatives with only four molecular descriptors which can be calculated directly from molecular structure alone.

PALLADIUM COMPLEXES SUPPORTED ON HYBRID ORGANIC-INORGANIC ZIRCONIUM PHOSPHITE : SELECTIVITY IN THE HECK REACTION

Abstract Supported palladium complex on zirconium phosphite-phosphonate was made from triphenylphosphine phosphonic acid. The supported catalyst showed significant selectivity in the competitive Heck reaction between iodobenzene and different iodobenzoates. The reaction seems to take place between the lamellar of the catalyst.

An Easy Formation of Dithioacetals on Alumina-KF Under Microwave Irradiation. Synthesis of new Potential Antiviral Phosphonates

Abstract The preparation of dithioacetals by the reaction of methylene compounds with S-methyl methanesulfonothioate on Al2O3-KF is described. Microwave irradiation without solvent provides a powerful activation. Potential antiviral phosphonates are prepared.

Potassium Fluoride on Alumina: Synthesis of O-Aryl N,N-Dimethylthiocarbamates and their Rearrangement into S-Aryl N,N-Dimethyl-Thiocarbamates Under Microwave Irradiation

Abstract A series of O-aryl N,N-dimethyl thiocarbamates have been prepared by the reaction of dimethylthiocarbamoyl chloride with phenols absorbed on potassium fluoride on alumina. The rearrangement of O-aryl N,N-dimethylthiocarbamate into S-aryl N,N-dimethyl thiocarbamate under microwave irradiation was also studied. The use of conductive support like graphite or silicon carbide allow these rearrangements although the O-aryl N,N-dimethylthiocarbamates have very low dielectric lost.

Artificial neural networks: Non-linear QSAR studies of HEPT derivatives as HIV-1 reverse transcriptase inhibitors

Structure-anti HIV activity relationships were established for a sample of 801-[2-hydroxyethoxy-methyl]-6-(phenylthio)thymine(HEPT) using a three-layer neural network (NN). Eight structural descriptors and physicochemical variables were used to characterize the HEPT derivatives under study. The networks architecture and parameters were optimized in order to obtain good results. All the NN architectures were able to establish a satisfactory relationship between the molecular descriptors and the anti-HIV activity. NN proved to give better results than other models in the literature. NN have been shown to be particularly successful in their ability to identify non-linear relationships.

Anionic activation of organic compounds by adsorption on alumina and alumina–KF

Condensations of acidic carbon compounds with piperonal (1) were achieved by adsorption on neutral alumina without solvent for the more acidic compounds and on Al2O3–KF for the less acidic compounds; dry Michael condensations also took place on Al2O3–KF.

Neural networks studies : quantitative structure-activity relationships of antifungal 1-[2-(substituted phenyl)allyl]imidazoles and related compounds

Models of relationships between structure and antifungal activity of 1-[2-(substituted phenyl)allyl]imidazoles and related compounds were constructed by means of a multilayer neural network using the back-propagation (BP) algorithm. Each molecule was described by three structural and one physicochemical parameters. The leave-one-out procedure was used to assess the predictive ability of a neural network model. The results obtained were compared to those given in the literature by the multiple linear regression (MLR), and were found to be better. The contribution of each descriptor to the structure-activity relationships was evaluated. Hydrophobicity of the molecule was confirmed to take the most relevant part in the molecular description.

Stereoselective enolization of methyl dithiopropanoate by adsorption on alumina−potassium fluoride

Alkylation of methyl dithiopropanoate with benzyl chloride at room temperature by adsorption on alumina-potassium fluoride is more selective than in solution under selected conditions (Pri2NLi; -70 °C).

A new radical decarboxylation reaction for the conversion of carboxylic acids into hydrocarbons

The esters of trans-9-hydroxy-10-phenylthio-or -10-chloro-9,10-dihydrophenanthrene are smoothly reduced under neutral conditions by tri-n-butylstannane to furnish, by radical elimination, phenanthrene and the nor-hydrocarbon formed from decomposition of the corresponding acyloxy radical.

Formation of dithianes and dithiolanes catalysed by clay. An unexpected functional selectivity

Montmorillonite KSF at room temperature without solvent catalyses the synthesis of dithiolanes and dithianes from carbonyl compounds; chemoselectivity in dithiane and dithiolane formation is observed between aromatic aldehydes and ketones and between aromatic and aliphatic aldehydes.