Natural products have historically been a mainstay source of anticancer drugs, but in the 90's they fell out of favor in pharmaceutical companies with the emergence of targeted therapies, which rely on antibodies or small synthetic molecules identified by high throughput screening. Although targeted therapies greatly improved the treatment of a few cancers, the benefit has remained disappointing for many solid tumors, which revitalized the interest in natural products. With the approval of rapamycin in 2007, 12 novel natural product derivatives have been brought to market. The present review describes the discovery and development of these new anticancer drugs and highlights the peculiarities of natural product and new trends in this exciting field of drug discovery.

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The present work reports the hydrolysis of ions of the series of lanthanides (III) and actinide (IV) elements in dilute aqueous solutions. It has been systematically examined in the presence of sodium perchlorate, which has been used for maintaining the solution at constant ionic strength. The number, the nature of the species in solution and their hydrolysis constants logb 10i for all ions at I = 0.1 mol dm -3 and at 25°C were determined by different softwares: Superquad and Sirko_P. A pH-potentiometric method was used with glass electrodes to determine the equilibrium constants K i :n+ represents Ce 3+ , Pr 3+ , Nd 3+ , Eu 3+ , Sm 3+ and Th 4+ ions. For the lanthanides, hydrolysis increases with the increase of the atomic number and the contraction of the ionic radius. The Th 4+ ion undergoes significant hydrolysis. To cite this article: E. Bentouhami et al., C. R. Chimie 7 (2004). RésuméCette étude concerne l'hydrolyse des ions de la série lanthanides (III) et du thorium (IV) ; elle a été effectuée en présence de perchlorate de sodium, utilisé pour maintenir constante la force ionique des solutions I, égale à 0,1 mol dm -3 . Le nombre et la nature des espèces en solutions, ainsi que leurs constantes d'hydrolyse logb 10i , ont été déterminées à 25°C à l'aide de différents softwares de calculs, à savoir, Superquad et Sirko_P. Une méthode potentiométrique est utilisée sur électrode de verre pour déterminer les constantes d'équilibres K i :OH) (n−1)+ + H + où M n+ représente les ions Ce 3+ , Pr 3+ , Nd 3+ , Eu 3+ , Sm 3+ et Th 4+ . Pour les lanthanides, l'hydrolyse augmente avec le numéro atomique et la diminution du rayon atomique. On montre que l'ion Th 4+ subit l'hydrolyse de manière significative. Pour citer cet article : E. Bentouhami et al., C. R. Chimie 7 (2004).

A series of polynuclear assemblies based on ligand L (1,4,7-tris[hydrogen (6-methylpyridin-2-yl)phosphonate]-1,4,7-triazacyclononane) has been developed. The coordination properties of ligand L with Ln (Ln = La, Eu, Tb, Yb, Lu) have been studied in water (pH = 7.0) and in DO (pD = 7.0) by UV-absorption spectrometry, spectrofluorimetry, H andP NMR, DOSY, ESI-mass spectrometry, and X-ray diffraction. This nonadentate ligand forms highly stable mononuclear complexes in water and provides a very efficient shielding of the Ln cations, as emphasized by the very good luminescence properties of the Yb complex in DO, especially regarding its lifetime (τ = 10.2 μs) and quantum yield (ϕ = 0.42%). In the presence of excess Ln cation, polynuclar complexes of [(LnL)Ln ] stoichiometry (x = 1 and x = 2) are observed in solution. In the solid state, a dinuclear complex of La could be isolated and structurally characterized by X-ray diffraction, unraveling the presence of strong hydrogen bonding interactions between a La(HO) cation and the [LaL] complex.

An ew wayo fi ntroducingaN-heterocyclic carbene cap onto cyclodextrinsh as been devised. The benzimidazolium intermediatesw ere found to behavea s receptors towards cavity matching anions. The corresponding C 1 -a nd C 2 -symmetrical regioisomericc arbene gold(I) complexes have been tested in ab enchmark asymmetric cycloisomerization of 1,6-enynes. Up to 50 % ee was achieved for the enantioselectivec ycloisomerization of N-allyl-4-methyl-N-(3-phenylprop-2-yn-1-yl)benzenesulfonamide.Confining cavity-shaped ligands are increasingly popular in catalysis because of their capacity to controlt he first coordination sphere of metals and in doing so produce unusual selectivities during metal-catalyzed reactions. [1] However,t heir use in asymmetric catalysis remains scarce due to the lack of suitable chiral macrocyclicr eceptors. [2] Amongst them, the naturally-occurring cyclodextrins (CDs) [3] occupy ap lace of choice as they are cheap, enantiopure, available in different sizes, and can be easily derivatized at specific locations.S of ar,m ost efforth as concentrated on asymmetric catalytic reactions taking place in water to take advantage of the host-guest properties of CDs in this medium. [4] It is only recently with the advent of new ways of functionalizing CDs [5] that ligandsw ith rigidified donor atomsh ave been able to force am etal centert or eside inside the CD cavity in organic media, resulting in very promising selectivities, in particular stereoselectivity,f or severalm etal-catalyzed reactions. [6] Achieving such ad esirable outcome in gold(I) catalysis [7] still constitutes to date ah ighly challenging targeti np articular for mononuclear complexes sincet he gold catalyticc enter needstob easc lose as possible to the selectivity-inducing steric environment as for example in helicenebased systems. [8] Such af eature can also be achievedb yc onfining N-heterocyclic carbenel igands (NHCs) derived from perbenzylated CDs, as recently shown by Sollogoub et al. [6a,e] The correspondingm ono-gold complexesg ave rise to promising enantio-and ring-size selectivities in two different enyne cycloizomerization reactions. So far,n either their permethylated counterparts, nor C 1 -symmetrical AC-capped derivatives have been tested. Having ar athera ccessible cavity compared with their benzylated analogues, such confining NHC ligandss hould be suitable for sterically more demanding enyne substrates. Moreover,f ollowing our previouss tudies on anion encapsulation in metalloCDs, [9] we wondered whether we could achieve the same properties with metal-free imidazolium-capped CDs. Herein, we present an ew way of introducingaNHC cap onto CDs, the capacity of benzimidazolium-capped, methylated CDs to behave as middle-sized anion receptors, and the catalytic properties of gold complexesd erived from both C 1 -a nd C 2symmetrical NHC-capped, methylatedC Ds in the asymmetric cycloisomerization of 1,6-enynes.Contrary to their perbenzylated analogs, permethylated CDs could not be capped with an imidazolium or benzimidazolium unit...

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