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Optical enrichment of dansyl‐rac‐amino acids by formation of crystalline inclusion complexes with cyclodextrins
Author(s) -
Jin Heng L.,
Stalcup Apryll,
Armstrong Daniel W.
Publication year - 1989
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.530010207
Subject(s) - chemistry , norleucine , enantiomeric excess , enantiomer , cyclodextrin , phenylalanine , recrystallization (geology) , crystallization , inclusion compound , racemization , mother liquor , chromatography , organic chemistry , leucine , amino acid , enantioselective synthesis , paleontology , biochemistry , biology , catalysis
Optical enrichment from racemic dansyl‐leucine, dansyl‐norleucine, and dansyl‐phenylalanine with both β‐ and γ‐cyclodextrins in water is reported. Initial crystallization yielded the dansyl‐ L ‐leucine isomer complexed in excess with β‐cyclodextrin with an optical purity of 62–78% depending on experimental conditions. The optical purities obtained for L ‐norleucine and L ‐phenylalanine were 71 and 64%, respectively. The optical purity can be increased with continued recrystallization. The dansyl‐ D ‐leucine isomer was obtained in the mother liquor with an optical purity of 54–93% depending on experimental conditions. The optical purities obtained for D ‐norleucine and D ‐phenylalanine were 72 and 58%. The optical purity of the isomer depended on the molar ratio of host:guest and the pH value of the solution. Optimum enrichment of both enantiomers was achieved with host:guest ratios of 2 : 1 and 3 : 1. Although maximum crystalline yield of the dansyl‐leucine/CD inclusion complex was obtained at a pH of 3.5, optical purity of both enantiomers was less than that obtained at other pHs. The influence of the molar ratio of host:guest and the pH value of the solution are discussed. This method is suitable for large‐scale enantiomeric separations.