Jacques Uziel

Huisgen cycloaddition reaction of C-alkynyl ribosides under micellar catalysis: synthesis of ribavirin analogues.

Carbonated analogues of ribavirin were synthesized from ethyl C-ribosylpropiolate obtained by an alkynylation reaction mediated by indium(0). The C-ribosides were then engaged in a Huisgen 1,3-dipolar cycloaddition reaction under a micellar catalysis. In these conditions, formation of 1,2,3-triazoles with control of the regioselectivity was observed. The regiochemistry of the adducts was determined by HMBC 2D-NMR analysis.

Chemo-, regio- and stereoselective conversion of P-chirogenic phosphorus borane complexes into their PO or PS derivatives

Abstract Chiral and achiral organophosphorus borane complexes are readily transformed into their corresponding phosphoryl or thiophosphoryl compounds in high yields using one-pot procedures with stereoselectivities reaching 100% in many cases. Both oxidation and sulfuration were performed under neutral or mild conditions and were applied to various organophosphorus borane complexes (phosphines, phosphinates, chlorophosphines, aminophosphines, etc.). In the case of the dissymmetric diphosphine or aminophosphine phosphinite ligands, the reaction of their diborane complexes proceeds regiospecifically to a single phosphorus group, affording the corresponding hybrid derivatives.

NMR enantiodifferentiation of triphenylphosphonium salts by chiral hexacoordinated phosphate anions

Abstract BINPHAT anion—rather than TRISPHAT—is an efficient NMR chiral shift reagent for triphenylphosphonium salts containing stereogenic centers on the aliphatic side-chain.

Monohydroxylation of cyclic and acyclic β-keto esters with molecular oxygen catalyzed by cobalt(II) chloride in neutral conditions†

Abstract Cyclic and acyclic α-alkyl-α-hydroxy-β-keto esters 2 were obtained with 50–100% isolated yields from the corresponding β-keto esters 1 by oxidation with molecular oxygen in a mixture of CH 3 CN/ i -PrOH and in the presence of cobalt(II) chloride.

A practical synthesis of chiral and achiral phosphonium salts from phosphine borane complexes

Abstract Phosphine borane complexes are transformed under mild conditions, in presence of an olefin, into quaternary phosphonium salts by reaction with an alkyl (or aryl) halide. In the case of the reaction of ( R )-PAMP.BH 3 1e with benzyl bromide, the enantiomerically pure phosphonium salt 3h is obtained.

Direct C-glycosylation by indium-mediated alkynylation on sugar anomeric position.

Indium-mediated alkynylation reaction was studied for the direct preparation of C-glycosides. Easily available starting sugar derivatives with an acetyl group at the anomeric position were tested as electrophiles toward alkynylindium reagents under Barbier conditions. Good yields and stereoselectivities were observed during the reaction. The alkynylation was applied to the synthesis of an alpha-(1-->6)-C-disaccharide analogue of isomaltoside.

1H and 31P NMR determination of the enantiomeric purity of quaternary phosphonium cations using TRISPHAT as chiral shift agent

The enantiomeric purity of quaternary phosphonium cations can be easily determined in 1H and 31P-NMR using TRISPHAT anion as chiral shift agent.

Synthesis of α -aminophosphonic acids by Pd(O) alkylation of diethyl aminomethylphosphonate schiff bases.

Abstract γ, δ -Unsaturated α -amino phosphonic acids are obtained by alkylation of Schiff bases 2 , 3 in the presence of a palladium catalyst under neutral or basic conditions in THF or DME, using allylic carbonates, esters or halides (50–80 % yields).

Indium-mediated alkynylation of sugars: synthesis of C-glycosyl compounds bearing a protected amino alcohol moiety

The coupling of glycals with an alkynyl iodide bearing a protected amino alcohol moiety was achieved in the presence of metallic indium under Barbier conditions. It gave functionalized C-glycosyl compounds, precursors of C-glycosyl amino acids with α configuration.

Electrophilic ring opening of oxazolines derived from serine and threonine: A practical entry to N(N)-protected β-halogeno α-aminoesters

Abstract Treatment of oxazolines 4a – c derived from serine or threonine with chloroformates, leads to the oxazoline ring opening and to the formation of N,N-protected β-chloro-α-aminoesters 1a – e in 30–88% isolated yields. In the presence of NaI (0.9 equiv), oxazolines 4a , b , d react with ethyl chloroformate to afford the N,N-protected β-iodo α-amino esters 1f–h (67–89% yields), whereas the reaction of 4a , b with trimethylsilyl halide gives the analogous N -benzoyl β-halogeno derivatives 1i , k with 30–86% yields.