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- Title
Cellulose chiral induction during the synthesis of cellulose N-phthaloyl-amino acid esters.
- Authors
Vanthuyne, Nicolas; Roussel, Christian
- Abstract
Cellulose was acylated by N-phthaloyl amino acid chlorides in the presence of pyridine to prepare an original library of cellulose N-phthaloyl-amino acid esters as chiral solid supports for enantioselective adsorption of racemates. Cellulose esters derived from N-phthaloyl glycine, alanine, valine, leucine, phenylalanine, phenylglycine and isoleucine were isolated in high yields and with degrees of substitution approaching 3. Interestingly, the use of an optically pure ( d or l) or a rac-amino acid led to the same cellulose ester according to (1) the measured optical rotation, (2) the enantiomeric excesses of the amino acids resulting from a non-racemising and total hydrolysis and (3) the enantioselective adsorptions of rac-benzoin, rac-Pirkle's alcohol and rac-Tröger's base. This suggests that either the formation of a prochiral ketene intermediate which was diastereoselectively attacked by the cellulose alcohols or, alternatively (or concomitantly), the occurrence of a chiral induction in the formed triesters during prolonged contact with the pyridine base in the reaction medium. Enantiomeric excesses in favour of the ( S) form ranged from 8 % to 50 % depending on the N-phthaloyl amino acid. The memory of the chirality of the starting material was lost and new chirality was imprinted by the cellulose backbone on the amino acid residues.
- Subjects
CELLULOSE; ENANTIOSELECTIVE catalysis; AMINO acids; ESTERS; GLYCINE
- Publication
Cellulose, 2013, Vol 20, Issue 4, p2057
- ISSN
0969-0239
- Publication type
Article
- DOI
10.1007/s10570-013-9946-y