87974-75-2Relevant academic research and scientific papers
Stereoselective Alkylation of Dianions derived from Chiral Half-Esters of Monosubstituted Malonic Acids: Asymmetric Synthesis of α-Alkyl α-Amino Acids and Key Synthetic Intermediates for Hunteria and Aspidosperma Indole Alkaloids
Ihara, Masataka,Takahashi, Masanobu,Taniguchi, Nobuaki,Yasui, Ken,Niitsuma, Hiroko,Fukumoto, Keiichiro
, p. 525 - 535 (2007/10/02)
Substitution of the chiral half-esters of monosubstituted malonic acids with halides leads to the formations of mixtures of the diastereomeric alkyl- or benzyl-malonic half-esters.The (R)-isomers (13A and 15A-22A) were obtained from the phenylmenthyl half-ester 14 of methylmalonic acid in high diastereoisomeric excess.The same stereoisomers were also produced by reaction of the half-esters 9, 23 and 24 with methyl iodide.Their absolute configurations were determined by transforming the major products into the known α-alkyl α-amino acid derivatives 30, 33 and 35.The major product 43, prepared by allylation of the half-ester 9, was converted into two lactones 41 and 42, key intermediates for synthesis of indole alkaloids of the Hunteria and Aspidosperma types.The mechanism of the above alkylation is discussed.
ALKYLATION AND PROTONATION OF CHIRAL SCHIFF BASES: DIASTEREOSELECTIVITY AS A FUNCTION OF THE NATURE OF REACTANTS
Tabcheh, Mohamed,Achqar, Abdelrhani El,Pappalardo, Louis,Roumestant, Marie-Louise,Viallefont, Philippe
, p. 4611 - 4618 (2007/10/02)
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.
REACTIONS OF SCHIFF BASE ANIONS WITH ELECTROPHILES: ROLE OF THE INITIAL STEREOCHEMISTRY
El Achqar, Abdelrhani,Roumestant, Marie-Louise,Viallefont, Philippe
, p. 2441 - 2444 (2007/10/02)
It is shown that the reactivity towards electrophiles of diastereomeric Schiff bases of *R and *S valine, leucine, phenylalanine and norvaline methyl esters with (1S,2S,5S) or (1R,2R,5R) 2-hydroxy 3-pinanone, is highly dependent on the stereochemistry of the starting product.
SYNTHESE ASYMETRIQUE D'ACIDES AMINES α-DISUBSTITUES
Bajgrowicz, J. A.,Cossec, B.,Pigiere, Ch.,Jacquier, R.,Viallefont, Ph.
, p. 3721 - 3724 (2007/10/02)
α-Disubstituted amino acids are prepared with good optical yields by enantioselective substitution using Schiff bases between α-monosubstituted amino acids and (S,S,S) or (R,R,R)-2-hydroxypinan-3-one as chiral reagent.The configuration of these acids is found to be dependent on the shielding effect of their aliphatic chain in the intermediary Schiff dianion.
