A new and preparatively useful method for the synthesis of non racemic alpha-trifluoromethyl (Tfm) alpha-amino acids (AAs) is presented. Key-building blocks are the sulfinimines (S)-1a,b, prepared via Staudinger reaction from trifluoropyruvic esters and the chiral N-sulfinyl iminophosphorane (S)-5, which were reacted with benzyl and alkylmagnesium halides. The resulting N-sulfinyl alpha-Tfm alpha-amino esters 6a,b and 6c-g, respectively, were produced with opposite stereoselectivity. The stereocontrol with alkyl Grignard reagents was progressively higher with increasing steric bulk. Some of the adducts 6 were transformed into alpha-Tfm-phenylalanine (R)-8 (with regeneration and recycling the chiral auxiliary), alpha-Tfm-leucine (S)-11c, alpha-Tfm-butyrine (S)-11f and alpha-Tfm-alanine (S)-11g in two steps in one-pot. (C) 1998 Elsevier Science Ltd. All rights reserved.

Sulfinimines of Trifluoropyruvate: Novel Intermediates for Chiral non Racemic alpha-Trifluoromethyl alpha-Amino Acids

CRUCIANELLI, MARCELLO;
1998-01-01

Abstract

A new and preparatively useful method for the synthesis of non racemic alpha-trifluoromethyl (Tfm) alpha-amino acids (AAs) is presented. Key-building blocks are the sulfinimines (S)-1a,b, prepared via Staudinger reaction from trifluoropyruvic esters and the chiral N-sulfinyl iminophosphorane (S)-5, which were reacted with benzyl and alkylmagnesium halides. The resulting N-sulfinyl alpha-Tfm alpha-amino esters 6a,b and 6c-g, respectively, were produced with opposite stereoselectivity. The stereocontrol with alkyl Grignard reagents was progressively higher with increasing steric bulk. Some of the adducts 6 were transformed into alpha-Tfm-phenylalanine (R)-8 (with regeneration and recycling the chiral auxiliary), alpha-Tfm-leucine (S)-11c, alpha-Tfm-butyrine (S)-11f and alpha-Tfm-alanine (S)-11g in two steps in one-pot. (C) 1998 Elsevier Science Ltd. All rights reserved.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11697/5806
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