Ring opening of oxazolines, prepared from L-serinates, with trimethylsilyl halides (TMSX) led to -halogeno-N-benzoyl- -amino esters in good to excellent yields. Quaternization of triphenylphosphine by the -bromo or -iodo amino esters gave the corresponding -phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl--amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding -halogeno-N-benzoyl--amino acids in 70–95% yields. Quaternization of triphenylphosphine by the bromo or iodo derivatives led to the phosphonium salts bearing a free acid function in 95% yield, without racemization. The efficiency of this synthesis was demonstrated by the preparation of these phosphonium salts in excellent overall yields, by a one-pot procedure starting from the oxazoline.
EFFICIENT SYNTHESIS OF BETA-HALOGENO PROTECTED L-ALANINES AND THEIR BETA-PHOSPHONIUM DERIVATIVES / F. MEYER; A. LAAZIRI; A.M. PAPINI; J. UZIEL; S. JUGÉ. - In: TETRAHEDRON-ASYMMETRY. - ISSN 0957-4166. - STAMPA. - 14:(2003), pp. 2229-2238. [10.1016/S0957-4166(03)00484-1]
EFFICIENT SYNTHESIS OF BETA-HALOGENO PROTECTED L-ALANINES AND THEIR BETA-PHOSPHONIUM DERIVATIVES
PAPINI, ANNA MARIA;
2003
Abstract
Ring opening of oxazolines, prepared from L-serinates, with trimethylsilyl halides (TMSX) led to -halogeno-N-benzoyl- -amino esters in good to excellent yields. Quaternization of triphenylphosphine by the -bromo or -iodo amino esters gave the corresponding -phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl--amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding -halogeno-N-benzoyl--amino acids in 70–95% yields. Quaternization of triphenylphosphine by the bromo or iodo derivatives led to the phosphonium salts bearing a free acid function in 95% yield, without racemization. The efficiency of this synthesis was demonstrated by the preparation of these phosphonium salts in excellent overall yields, by a one-pot procedure starting from the oxazoline.File | Dimensione | Formato | |
---|---|---|---|
36-Terahedron_Asymmetry_2003_14_2229-2238.pdf
Accesso chiuso
Tipologia:
Versione finale referata (Postprint, Accepted manuscript)
Licenza:
Tutti i diritti riservati
Dimensione
264.81 kB
Formato
Adobe PDF
|
264.81 kB | Adobe PDF | Richiedi una copia |
I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.