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Synthesis of the First Chiral Bisindolyl Monomethinium Cyanine Dyes
Author(s) -
Eggers Lutz,
Buß Volker
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960618
Subject(s) - cyanine , chemistry , diastereomer , salt (chemistry) , indole test , stereochemistry , proton nmr , nuclear magnetic resonance spectroscopy , spectroscopy , organic chemistry , physics , quantum mechanics , fluorescence
The synthesis of the chiral monomethine cyanine dyes 8 and 9 starting with the achiral indole 1 is described. Key intermediates are the new chiral Fischer bases R ‐ and S ‐ 4 , which were separated after diastereomeric salt formation. The conformation of the dyes 8 and 9 is twisted di‐ Z , according to NOE and dynamic NMR spectroscopy. The free energy difference between oppositely twisted conformations is ca. 2.5 kJ mol −1 .