Visual enantiomeric recognition of amino acid derivatives in protic solvents

• Published in: Journal of organic chemistry Vol. 70; no. 12; pp. 4609 - 4616
• Main Authors: TSUBAKI, Kazunori, TANIMA, Daisuke, NURUZZAMAN, Mohammad, KUSUMOTO, Tomokazu, FUJI, Kaoru, KAWABATA, Takeo
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 10-06-2005
• Subjects: Aliphatic compounds; Amino Acids - analysis; Amino Acids - chemistry; Chemistry; Crown Ethers - chemistry; Exact sciences and technology; Molecular Structure; Organic chemistry; Phenolphthalein - chemistry; Preparations and properties; Solvents; Stereoisomerism; Temperature; Phenolphthalein; Crown ethers; Aminoacid; Enantiomer; Molecular recognition; Inclusion compound; Protic solvent
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo050387u

Various types of chiral host molecules 2-7 based on a phenolphthalein skeleton and two crown ethers were prepared for use in visual enantiomeric recognition, and we examined their enantioselective coloration in complexation with chiral amino acid derivatives 9-22 in methanol solution. Methyl-substituted host (S,S,S,S)-3 showed particularly prominent enantiomer selectivity for the alanine amide derivatives 11 and 12. A combination of methyl-substituted host (S,S,S,S)-3 with guest (R)-11 or (R)-12 developed a purple color, whereas no color development was observed with (S)-11 or (S)-12. On the other hand, phenyl-substituted host (S,S,S,S)-6 showed deeper coloration with a wide range of (S)-beta-amino alcohols compared to that seen with host (S,S,S,S)-6 and the corresponding (R)-beta-amino alcohols at 0 degrees C. Furthermore, absorbance inversion temperatures (AIT) were observed within the range of 0-50 degrees C in many cases.