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Synthesis and evaluation of a new water‐soluble fluorescent red dye, xanthene bis‐ C ‐glycoside
Author(s) -
Sato Shingo,
Nojiri Toshikatsu,
Okuyama Nao,
Maeda Koya,
Kirigane Aoi
Publication year - 2020
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.4050
Subject(s) - xanthene , chemistry , glycoside , fluorescence , glyoxylic acid , aqueous solution , pyridine , alizarin red , medicinal chemistry , organic chemistry , staining , physics , quantum mechanics , medicine , pathology
Condensation of 2 eq. of C ‐ β ‐D‐glucosylphloroacetophenone with glyoxylic acid in an aqueous solution of Na 2 CO 3 , followed by air oxidation in MeOH in the presence of 11 eq. of pyridine to afford a 36% yield of a bright red dye, xanthene bis‐ C ‐glycoside. This dye is 10 times more fluorescent (Φ f [EtOH] 581 nm = 3.9 × 10 −2 ) and 7.5 times more water‐soluble (57 mg/mL H 2 O) than the natural red pigment, carthamin. Detailed NMR analysis of its methyl analogs was used to confirm the structure of the dye as methyl 4,5‐diacetyl‐1,3,8‐trihydroxy‐3‐oxo‐3 H ‐2,7‐di‐ C ‐ β ‐D‐glucopyranosylxanthene‐9‐carboxylate from among three possible ring‐closure isomers. Xanthene is safe and shows high light‐resistance; therefore, xanthene bis‐ C ‐glycoside could be used as a food colorant or an in vivo probe.