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Ruthenium complexes catalyze the oxidation of alcohols to the corresponding ketones or aldehydes when Ca(OCl)2 or NaIO4 are used as oxygen donors in the presence of water (5–10 equiv.). The reactions take place at room temperature affording products in yields of 45–80%.

Metal-catalyzed cycloisomerization reactions of 1,n-enynes have appeared as conceptually and chemically highly attractive processes as they contribute to the highly demanded search for atom economy and allow the discovery of new reactions. Since the pioneering studies with palladium by the research group of Barry Trost in the mid-1980s, several other metals have been identified as excellent catalysts for the rearrangement of enyne skeletons. Moreover, the behavior of 1,n-enynes may be influenced by other functional groups such as alcohols, aldehydes, ethers, alkenes, or alkynes, thus enhancing the molecular complexity of the synthesized products. Apart from the intrinsic rearrangements of 1,n-enynes, several tandem reactions incorporating intramolecular trapping agents or intermolecular partners have been discovered. This Review aims to highlight the main contributions in this field of catalysis and to propose and comment on the mechanistic insights of the recent discoveries.

The removal of allylic protecting groups promoted by the catalytic system Pd(OAc)(2)/TPPTS has been achieved on bifunctional substrates with complete chemoselectivity and high efficiency, in aqueous media. By lowering the amount of palladium catalyst, substituted allylic carboxylates remained unaffected while allylcarbamates, in the same molecule, were quantitatively removed. When using a biphasic C3H7CN-H2O solvent, the water-soluble catalyst could also differentiate allylcarbonates from dimethylallylcarbamates on diprotected amino alcohols. All these reactions were carried out under mild and neutral conditions which are compatible with a large range of molecules including beta-lactams.

The synthesis of spermidine derivatives holding three independently removable N-protecting groups has been achieved from diallylamine using the key sequence : selective palladium-catalyzed monodesallylation of diallylamines / N-alkylation.

Peptides can be easily synthesized according to a stepwise strategy in solution without any purification. The selective removal of allyloxycarbonyl protecting groups catalyzed by a water-soluble palladium catalyst constitutes the key step of the peptide chain elongation. (C) 1997 Published by ElsevierScience Ltd.

The title compounds were conveniently synthesized by efficient sequential one-pot amination-alkylation starting from (Z)-4-acetoxy-2-butenyl ethyl carbonate (3) with tert-butyl (tert-butoxycarbonyloxy)carbamate, dimethylamine and methyl (diphenylmethyleneamino) acetate. Hydrogenation and hydrolysis of the 1,4-adducts afforded N 6 -hydroxylysine [2-amino-6-(hydroxyamino)hexanoic acid, 1) and laminine hydrochloride [2-amino-6-(trimethylammonio)hexanoic acid chloride, 2] in 65% and 39% yield, respectively

Ce manuscrit présente le développement d'une méthode de synthèse de motifs polypropionates et son application à la synthèse totale de deux molécules naturelles cytotoxiques : le Dolabélide A et le (+)-Discodermolide. Cette méthode, par analogie avec les voies de biosynthèse des polypropionates, permet la synthèse séquentielle et itérative de ces motifs par l'association de trois réactions : l'hydrogénation asymétrique de béta-cétoesters et de béta-hydroxycétones catalysée par des complexes chiraux du ruthénium, la méthylation diastéréosélective de Fráter-Seebach et la condensation de Claisen. Pour le Dolabélide A, deux fragments avancés ont été préparés, et 7 des 11 centres stéréogènes ont été installés par hydrogénation asymétrique avec des sélectivités supérieures à 95 %. Pour le (+)-Discodermolide, trois fragments intermédiaires ont été élaborés et 10 centres stéréogènes mis en place dont 7 par hydrogénation asymétrique ou méthylation diastéréosélective, ici encore avec des sélectivités supérieures à 95 %.