Jacques Daunis

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.

Asymmetric synthesis of ketoprofen : A surprising base catalyst effect during asymmetric addition of pantolactone to methyl (3-benzoylphenyl) ketene

Abstract The best diastereoselectivity of addition of a chiral alcohol to the ketene derived from ketoprofen was obtained with R or S pantolactone (ed=99%). Depending on the tertiary amine used both for ketene formation and as catalyst during addition, the diastereoisomeric ratio of esters could be strongly modified and even inverted. Mild saponification afforded R or S ketoprofen in enantiomeric excess of up to 99%.

Supramolecular asymmetric induction : A new concept applied to the supported enantioselective synthesis of α-amino acids

Abstract A polyacrylic resin with pendant chirality has been used as a chiral auxiliary. The prochiral ester enolate, reversibly linked to the polymer chain via a Schiff base, is surrounded by chiral pendants, allowing supramolecular asymmetric induction to occur. Amino acids with enantiomeric excesses up to 88–89% could be synthesized from supported glycine t-butyl ester enolate by reaction with alkyl halides. Enantioselective protonation depends on the initial configuration of the supported aminoacid. Alanine was obtained in 90% ee by repetitive asymmetric protonation.

SYNTHESIS OF ENANTIOMERICALLY PURE 2-ALKYL 1-AMINO CYCLOPROPANE-1-CARBOXYLIC ACID

Abstract Asymmetric synthesis of 1-amino 2-alkyl cyclopropane carboxylic acids using (1R,2R,5R)-2-hydroxy pinan-3-one as the chiral auxiliary and Coreys ylide as reagent is described.

A convenient synthesis of optically active phenylglycine

Abstract Optically active R phenylglycine methyl ester hydrochloride ( ee = 98%) was prepared in 90% yield from racemic phenylglycine. The key step was the base catalysed diastereoselective addition at −78°C of R pantolactone to the N-phthalyl protected phenylglycine ketene

Determination of the chiral purity of benzylic amines using marfey's reagent

Abstract 1-Fluoro-2,4-dinitrophenyl-5-(S)-alanine amide (Marfeys reagent) was used as a chiral derivatizing agent for benzylic amines in order to determine optical purities.

Total synthesis and Ionophoric behaviour of a gramicidin A analogue.

Abstract A new gramicidin A analogue (GAA) containing a C-terminal β-alaninamide group instead of the natural ethanolamine moiety has been synthesized on a polyacrylic resin and examined after its incorporation into a black lipid membrane (BLM). Preliminary conductance data show that this peptide and the natural gramicidin both display the same ionophoric activity.

Asymmetric supported reactions: Synthesis of chiral amines

Abstract Deracemization of amines, linked via Schiff bases to a chiral polyacrylic polymer has been studied. An enantiomeric excess of 72% has been obtained with α-methyl benzylamine.

Diastereoselective cyclisation of 2-hydroxypinan-3-onyl amino esters

Abstract A totally diastereoselective cyclisation of esters resulting from partial resolution during the condensation of 2-hydroxypinan-3-one wifh various racemic α-amino acids via Schiff bases has been observed and provides a route to homochiral α-amino acids.

Improved synthesis of preformed Boc-aminoacid-bridging groups for use in solid phase peptide synthesis

Abstract Preformed Boc-aminoacid-bridging groups are synthesized by an improved method, using Tmse temporary protection of the starting 4-(halomethyl)phenylacetic acid or bromoacetic acid.