Jean-Claude Poulin
University of Paris-Sud
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Featured researches published by Jean-Claude Poulin.
Journal of Organometallic Chemistry | 1975
Tuan Phat Dang; Jean-Claude Poulin; Henri B. Kagan
Abstract Various chiral diphosphines related to diop, isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane, have been prepared. Substitution of a methyl group at the meta position of each aromatic ring increases optical yields, which can reach 90% (asymmetric synthesis of a 3-(3,4-dihydroxyphenyl)alanine derivative). Excellent results from asymmetric catalysis have also been obtained using structural analogues of diop in which the acetonide ring is placed by a carbon ring.
Optics Express | 2008
B. Poumellec; Matthieu Lancry; Jean-Claude Poulin; Santhi Ani-Joseph
We ascertain by measuring the surface topography of a cleaved sample in which damage lines have been written in volume by scanning with a femtosecond laser, that matter shearing occur along the laser track with alternating sign (scissor or chiral effect). We note that the shearing in the head of the laser tracks change its sign with the change in scanning direction (pen effect or non reciprocal writing). We also show that nanostructures in the head are nano-shearing, with all the same sign whatever the direction of writing may be. We suggest that symmetries revealed by the shearing mimic the laser induced electron plasma density structures and inform on their unusual symmetries induced by the laser beam structures.
Tetrahedron | 1984
Sana El-Baba; Jean-Claude Poulin; Henri B. Kagan
Abstract A racemic mixture of a compound bearing a reactive prochiral center can partially react with a chiral reagent ; diastereomeric products are formed and the starting material is kinetically resolved. The relationships between the relative amounts and the enantiomeric excesses of reaction products and recovered starting material are discussed. Applications are given for asymmetric hydrogenation of racemic AcΔPheAlaOMe catalyzed by a rhodiumdiop complex.
Journal of Organometallic Chemistry | 1975
Jean-Claude Poulin; Tuan-Phat Dang; Henri B. Kagan
Abstract The catalytic activity of Wilkinsons rhodium complexes with a diphosphine is studied in the hydrogenation of styrene and α-acetamido cinnamic acid. There is a large effect of the chain linking the two diphenylphosphino groups, which can change the selectivity of the obtained catalyst.
Tetrahedron-asymmetry | 1992
A. Hammadi; Jean-Marc Nuzillard; Jean-Claude Poulin; Henri B. Kagan
Abstract Protected (Z)dehydrophenylalanyl-Leu-enkephalin, (Z)dehydrotyrosyl-Leuenkephalin and (Z)dehydrotyrosyl-(R)Ala 2 -Leu-enkephalin. have been synthesized. These compounds have been hydrogenated to give protected Leu-enkephalins in the presence of various chiral rhodium complexes. Deprotection of the product gave Leu-enkephalins or epimers, ytterbium in liquid ammonia allows smooth deprotection of NHCBz or OTs groups on small amounts of peptides. Strong stereocontrol could be achieved by suitable choice of the chiral catalyst. This method has good potential for stereospecific labelling of enkephalins and other small peptides.
Tetrahedron | 1982
H. Levine-Pinto; J.L. Morgat; P. Fromageot; D. Meyer; Jean-Claude Poulin; Henri B. Kagan
Abstract Rhodium-(+)diop complex catalyzes the stereoselective addition of two tritium atoms in Ac-ΔPhe-( S ) PheOMe (diop stands for isopropylidene - 2,3 - dihydroxy - 2,3- bis - diphenylphosphino - 1,4 - butane). Tritiated Ac( S ) Phe-( S ) PheOMe and Ac-( R ) Phe-( S ) PheOMe were obtained with a theoretical specific radioactivity. Each diastereoisomer was isolated in a pure state, their 3 H-nmr spectra indicated the ratio and the sites (C α -C β ) of 3 H labelling. 3 H- 3 H and 1 H- 1 H coupling constants used together allowed the unequivocal assignment of the three staggered rotamers around C α -C β in the N-terminal phenylalanine moiety. The scope of the reaction for selective preparation of tritiated dipeptides is discussed.
Tetrahedron | 1986
S. El-Baba; Jean-Marc Nuzillard; Jean-Claude Poulin; Henri B. Kagan
Abstract Monodehydropeptides with the dehydroaminoacid fragment in C-terminal or N-terminal position were synthetized as well as a family with the general formula Ac-ΔPhe-(Gly) n -Leu-OR (n = 0–2, R H or Me). Asymmetric reduction of these compounds catalyzed by chiral rhodium complexes was investigated. The results were discussed in terms of double asymmetric induction. A method was developped to avoid the use of both enantiomers of the substrate or of the catalyst, it consists in the total reduction of a racemic dehydropeptide. The products distribution gives access to the two desired facial selectivities.
Tetrahedron Letters | 1986
Jean-Marc Nuzillard; Jean-Claude Poulin; Henri B. Kagan
Abstract (S,S)-Z-(0)Ts-Tyr-Gly 2 -ΔPhe-Leu-OMe was synthesized. Some chiral rhodium complexes catalyze the reduction of the CC bond. The stereochemistry of reduction of the ΔPhe moiety was investigated, 93 % de could be achieved with dipamp as ligand in the catalyst.
Journal of Molecular Catalysis A-chemical | 1995
Jean-Claude Poulin; Henri B. Kagan; Michael N. Vargaftik; Igor P. Stolarov; I. I. Moiseev
Abstract STM observation showed giant palladium-561 clusters which are larger in size than observed earlier by TEM and HREM studies. The difference is presumably due to the ligand shell of the clusters, which is invisible to electron microscopy.
Chemical Communications | 2003
Richard Gil; Jean-Claude Fiaud; Jean-Claude Poulin; Emmanuelle Schulz
Charge-transfer complexes have been detected by chemical force microscopy (CFM) between a tip and a substrate respectively functionalized with trinitrofluorenone and 9-anthracenemethanol siloxane derivatives.