Solvent exchanges among molecular compounds

Solid-solid transformations between solvates of pharmaceutical compounds are investigated under various conditions. In the case of Roxithromycin, it is shown that starting from single crystals of the acetonitrile solvate, a transformation towards the monohydrate occurs according to a cooperative mechanism. This smooth exchange of solvent probably involves a transport of matter within channels, and the comparison of crystal structures is consistent with the persistence of the main features of the 3D lattice. By contrast, starting from the DMSO solvate of Dexamethasone acetate, the transformation towards the sesquihydrated form, induced by the immersion of the DMSO solvate in water, is fully destructive and reconstructive. This occurs far-from-equilibrium and is therefore controlled by kinetic factors. The existence of an intermediate liquid phase within the particle is postulated to account for the appearance of whisker-like crystals growing first on high-energy sites of the former particle. An extended analysis of these transformations between solvates shows that they could be classified according to rules previously proposed in the case of desolvation mechanisms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dosage des composes phenoliques dans les extraits vegetaux par oxydation cuivrique en milieu non aqueux

(The spectrophotometric determination of phenolic compounds in vegetable extracts by oxidation with copper(II) in nonaqueous media)Oxidation with copper(II) in nonaqueous medium is used for the o-diphenolic compounds chlorogenic acid, rutin, pyrocatechol and epicatechol. A spectrophotometric study of the o-diphenol and o-quinone forms leads to the establishment of two systems of equations for the determination of these compounds. This study complements earlier results. The validity of the method is discussed on the basis of results obtained with Passe-crassane pear extracts.     

New heterocycles with cycloamidine substructure and their ringtransformation reactions with acetylene dicarboxylic ester

The synthesis of pyrido[2,1‐c]‐1,2,4‐triazines 6 , pyrido[1,2‐b]‐1,2,4‐triazines 7 and pyrido[1,2‐b]pyri‐dazines 8 respectively by cycloacylation of derivatives of pyridine with imidoylchlorides of type 2 is described. The heterocycles of type 6 as well as of type 7 can be ring‐transformed with dimethyl acetylenedicarboxylate. In contrast to pyrido[1,2‐a]pyrazines 1, a complex reaction including cleavage of the acetylene subunit takes place. Starting from compound 6a , the pyrrolo[2,3‐d]imidazole 11a could be isolated from a mixture of unidentified by‐products, whereas derivatives 7 gave nearly quantitatively the tricyclic products of type 12 .     

Grafting Dendrons onto Pillar[5]Arene Scaffolds

With their ten peripheral substituents, pillar[5]arenes are attractive compact scaffolds for the construction of nanomaterials with a controlled number of functional groups distributed around the macrocyclic core. This review paper is focused on the functionalization of pillar[5]arene derivatives with small dendrons to generate dendrimer-like nanomaterials and bioactive compounds. Examples include non-viral gene vectors, bioactive glycoclusters, and liquid-crystalline materials.