Monique Calmes

Preparation of Chiral Amino Esters by Asymmetric Phase‐Transfer Catalyzed Alkylations of Schiff Bases in a Ball Mill

The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase-transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75 %. Because an equimolar amount of starting material was used, purification was greatly simplified.

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.

How to build optically activeα-amino acids

SummaryVarious methodologies published in the literature dealing withα-amino carboxylic acid asymmetric synthesis are presented in a digest form. In each case, only some recent or most typical works are mentioned.

(S)-ABOC: a rigid bicyclic β-amino acid as turn inducer.

In order to investigate the ability of the (S)-aminobicyclo[2.2.2]octane-2-carboxylic acid 1 (H-(S)-ABOC-OH) to induce reverse turns into peptides, two model tripeptides, in which this bicyclic unit was incorporated into the second position, were synthesized and analyzed by FT-IR, CD, NMR, and X-ray studies.

Dynamic kinetic resolution of racemic N-phthalyl amino acids using (S)-α-methylpantolactone as the chiral auxiliary

Abstract A dynamic kinetic resolution of racemic N-phthalyl amino acids by stereoselective esterification was examined using (S)-α-methylpantolactone as the chiral auxiliary. The reaction of various racemic N-phthalyl amino acids with this chiral alcohol in the presence of both DCC and DMAP afforded predominantly the (S,S)-esters in nearly quantitative yield.

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%.

A general and accurate nmr determination of the enantiomeric purity of α-aminoacids and α-aminoacid derivatives

Abstract Derivatization of α-aminoacids, α-aminoesters and α-aminolactones as N-acetyl derivatives allow the accurate NMR determination of the enantiomeric purity. In these conditions the major coordination site with a chiral shift reagent will correspond to the NMR observation site. Experimental factors leading to the highest ΔΔδ values are ascertained. No straightforward correlation with absolute configurations can be established.

Asymmetric Synthesis of (S)-β2-Homoarylglycines

The synthesis of racemic N-phthalyl β2-homoarylglycines 5 and their asymmetric transformation have been investigated. The key step is the stereoselective addition of the (R)-pantolactone to the corresponding prochiral ketene 7.

Asymmetric synthesis of α-amino acids via diastereoselective addition of (R)-pantolactone to their ketenes

Abstract The diastereoselective addition of ( R )-pantolactone to various amino ketenes derived from phthalyamino acids is reported. The configuration of the newly-generated asymmetric center is dependent on alkyl Cα substitution. This method constitutes a novel and convenient way of amino acid deracemization.

Robust helix formation in a new family of oligoureas based on a constrained bicyclic building block.

BAC for more: a constrained bicyclic building block with urea linkages is an efficient combination for the formation of a highly rigid helical system. This type of bicyclic amino carbamoyl (BAC) foldamer was studied both in solution and in the solid state. A robust H-bond (dotted line) network was found between the carbonyl oxygen atoms (red) and the amino groups (dark blue) within the helix.