Philippe Viallefont

Alkylation and protonation of chiral schiff bases: Diastereoselectivity as a function of the nature of reactants

Abstract The factors controlling the diastereoselective alkylation and protonation reactions of chiral Schiff bases prepared from 2-hydroxypinan-3-one and α-aminoesters are reported: nature of the ester, of the alkylating agent and of the base.

Synthesis of enantiomerically pure (2R, 5S)- and (2R, 5R)-5-hydroxypipecolic acid from glycinate Schiff bases

Abstract An asymmetric synthesis of cis - and trans - 5-hydroxy-(D)-pipecolic acid, starting from glycinate Schiff bases is described. The approach involves the stereoselective alkylation to generate an unsaturated side chain which on cyclisation leads to the desired trans - or cis - 5-hydroxy-(D)-pipecolic acid.

Asymmetric synthesis of cis and trans 2-methyl and 2-ethyl 1-amino cyclopropanecarboxylic acids

Abstract A new four step asymmetric synthesis of 2-methyl and 2-ethyl 1-amino cyclopropane carboxylic acids resulted from the cycloaddition of diazomethane to the corresponding chirally derivatized dehydro-aminoacid.

Reactions of fluorobenzene tricarbonylchromium complexes with anions from schiff bases of α-amino esters ; enantioselective synthesis of α-aryl amino acids

Abstract We report here a convenient synthesis of α-substituted aryl amino acids via the addition of α-amino esters to fluorobenzene tricarbonylchromium complexes. Optically pure α-aryl amino acids have been prepared by enantioselective substitution of fluorobenzene complexes using Schiff bases of L-alanine, leucine and valine methyl esters and (1R,2R,5R)-2-hydroxypinan-3-one.

Synthesis of enantiomerically pure phosphonic analogues of homoserine derivatives

Abstract Enantiomerically pure phosphonic analogues of homoserine derivatives are synthesized the key-step being the diastereoselective alkylation of a chiral Schiff base.

New biocatalysts for peptide synthesis :Gels of copolymerized acrylic derivatives of α-chymotrypsin and polyoxyethylene

Abstract Copolymers of acrylated derivatives of α-chymotrypsin and polyethylene glycol (PEG*) have been prepared and used as biocatalysts for the synthesis of model peptides in organic solvent. AcTyrLeuNH 2 is quantitatively obtained even after a dozen of cycles.

Rapid solid phase synthesis of α-amino acids

Abstract A solid phase synthetic method for amino acids is developed. The N-acetyl-dehydroalanine is quatitatively bound to Wang resin by the Mitsunobu method. Then a Michael addition is achieved on the double bond with different nucleophiles. Non proteinic N-acetyl-α-amino acids are obtained after cleavage from the resin by mild acid treatment (Scheme 1).

Antitumoral cyclic peptide analogues of chlamydocin

A series of cyclic tetrapeptides bearing the bioactive alkylating group on an epsilon-amino-lysyl function have been examined for their antitumoral activity on L1210 and P388 murine leukemia cell lines. One analogue belonging to the chlamydocin family and bearing a beta-chloroethylnitrosourea group was found to be potent at inhibiting L1210 cell proliferation and had a higher therapeutic index than the reference compound bis-beta-chloroethylnitrosourea (BCNU) on the in vivo P388-induced leukemia model.

PYRROLIDINOPIPERAZINEDIONE AS CHIRAL AUXILIARY AND ITS USE IN ASYMMETRIC MANNICH SYNTHESIS

Abstract Functionalised diketopiperazines (DKPs) are easily obtained optically pure by disymmetrization of a mesopyrrolidine and can be easily converted to an α-amino amine containing compound. As a first example, one of the new chiral auxiliaries has been used to prepare an optically pure β-amino ester through a Mannich reaction.

Asymmetric synthesis of (2S,3R,4R)-ethoxycarbonylcyclopropyl phosphonoglycine

Abstract The synthesis of enantiomerically pure (2 S ,3 R ,4 R )-ethoxycarbonylcyclopropyl phosphonoglycine is described, the key-step involving 1,4-addition of a chiral enolate to ethyl 4-bromo-crotonate.