Chiral sulfonated phosphines. VIII. Hydrogenation of dehydropeptides in a two-phase system
Dehydropeptides have been reduced in a two-phase system using 2> associated with chiral water-soluble ligands derived from cyclobutanediop and BDPP.Diastereoselectivities of up to 87percent were obtained with tetrasulfonated BDPP.
Laghmari, M.,Sinou, D.,Masdeu, A.,Claver, C.
p. 213 - 216
(2007/10/02)
Lithium-salt effects in peptide synthesis. Part I: Conditions for the use of lithium-salts in coupling reactions
The influence of Li-salts on the course of peptide-coupling reactions was investigated. As a model for segment couplings, Ac-Phe-OH was coupled to HCl . H-Ala-OMe using the mixed anhydride, DCCl, DCCl/HOBt, BOPCastro and TBTU-Knorr methods. As a model for
Thaler, Adrian,Seebach, Dieter,Cardinaux, Francis
p. 617 - 627
(2007/10/02)
Effects of solvent and temperature on the 1,4-asymmetric induction in the diastereoselective hydrogenation of dehydrodipeptides
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Ikeda,Yamagishi,Yamaguchi,Hida
p. 3508 - 3512
(2007/10/02)
ASYMMETRIC HYDROGENATION OF DEHYDROAMINO ACIDS AND DEHYDRODIPEPTIDES WITH RHODIUM(I)-MODIFIED DIOP CATALYSTS.
( minus )-DIOP was modified in two ways: i), introduction of a large aromatic substituent at the dioxolane ring of ( minus )-DIOP and ii), replacement of one diphenylphosphino group by diarylphosphino group to give unsymmetrical DIOPs. Modification at the dioxolane ring had a small effect on the asymmetric induction by DIOP in the hydrogenation. Modification at the phosphino group affected the stereocontrol by the ligand and the unsymmetrical DIOP with di-2-naphthylphosphino group gave higher optical yields than ( minus )-DIOP for the hydrogenation of alpha -acetamidocinnamic acid and dehydrodipeptides.
Yamagishi,Yatagai,Hatakeyama,Hida
p. 1897 - 1901
(2007/10/02)
ASYMMETRIC HYDROGENATION OF DEHYDRODIPEPTIDES WITH RHODIUM(I)-CHIRAL DIPHOSPHINITES. SELECTIVE (S,S)- AND (R,R)-PRODUCT FORMATION BY DOUBLE ASYMMETRIC INDUCTION.
In the hydrogenation of dehydrodipeptides, the effect of chiral center of the substrate ((S) or (R)) on the asymmetric induction was examined using the catalysts of Rh(I)-chiral diphosphinite containing pyrrolidine moiety (POP). The catalysts with POP's h
Yatagai,Yamagishi,Hida
p. 823 - 826
(2007/10/02)
PARTIAL RESOLUTION THROUGH CHIRAL SYNTHESIS USING A RACEMIC MIXTURE
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.
El-Baba, Sana,Poulin, Jean-Claude,Kagan, Henri, B.
p. 4275 - 4284
(2007/10/02)
A NOVEL ROUTE TO DIPEPTIDE AND ITS DERIVATIVE BY MEANS OF THE PALLADIUM CATALYZED FACILE CLEAVAGE OF 1-(1-METHOXYCARBONYL)ALKYL-3-SUBSTITUTED-4-ARYLAZETIDIN-2-ONES
1-(1-Methoxycarbonyl)alkyl-3-substituted-4-arylazetidin-2-ones were found to be cleaved exclusively at the N-C4 bond by the hydrogenolysis on palladium catalyst to give the corresponding dipeptide and its derivative in excellent yields.
Ojima, Iwao,Suga, Shigemi,Abe, Rumiko
p. 3907 - 3910
(2007/10/02)
ASYMMETRIC SYNTHESIS OF DIPEPTIDES BY MEANS OF HOMOGENEOUS HYDROGENATION CATALYZED BY CHIRAL RHODIUM COMPLEXES
Asymmetric hydrogenation of dehydrodipeptides, α-acylaminocinnamoyl-(S)-amino esters catalyzed by rhodium complexes with chiral diphosphines gave either (R)-N-acylphenylalanyl-(S)-aminoesters or (S)-N-acylphenylalanyl-(S)-amino esters with high diastereom
Ojima, Iwao,Suzuki, Tadashi
p. 1239 - 1242
(2007/10/02)
Stereoselective Synthesis of Dipeptides by Asymmetric Reduction of Dehydropeptides Catalyzed by Chiral Rhodium Complexes
Asymmetric catalysis was used to control the creation of an asymmetric center in a chiral dehydropeptide.The reduction of Ac-ΔPhe-(S)-Phe-OR (R=H or Me) was studied as a model.Depending on the type of chiral rhodium catalyst used, it was possible to selec
Meyer, Dominique,Poulin, Jean-Claude,Kagan, Henri B.,Levine-Pinto, Huguette,Morgat, Jean-Louis,Fromageot, Pierre
p. 4680 - 4682
(2007/10/02)
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