Efficient Fluorescein Spirolactam and Bis-Spirolactam Synthesis

Synthesis of taurine–fluorescein conjugate and evaluation of its retina-targeted efficiency in vitro

“…Surprisingly, we found the intensely red-orange active ester solution was converted into a nearly colorless solution after the reaction and the non-fluorescent white solid (F–Tau) was isolated by preparative HPLC. The resulting F–Tau was in a closed, spirolactam form, consistent with the results of Adamczyk and Grote 26 . This configuration was confirmed by the characteristic spirolactam peak near 64 ppm in the 13 C NMR spectrum ( Supplementary Fig.…”

“…The synthetic pathway for F–Tau is illustrated in Scheme 1 . Traditionally, fluorescein has been viewed to exist in two forms ( Scheme 2 ): a highly fluorescent, open, quinone form and a non-fluorescent, closed, spirolactone form 26 . In order to obtain F–Tau, the first step involved the activation of fluorescein because it was difficult to react with primary amines like taurine when the carboxyl group was masked.…”

Investigating rhodamine B‐labeled peptoids: Scopes and limitations of its applications

“…Nevertheless, the possibility of cyclization can also be a drawback for common fluorescence microscopy experiments. Adamczyk and Grothe showed that fluorescein methyl ester reacts rapidly with a variety of primary amines in N , N ‐dimethylformamide (DMF) at ambient temperature to form colorless compounds 13. Labeled peptides and peptoids demonstrate similar effects if they are covalently bound with these fluorescent dyes via a primary amide bond at the carboxyphenyl group: Often aminohexanoic acid (Ahx) serves as a spacer between the biomolecules and the fluorophore to avoid quenching and steric interactions.…”

Cell Compatible Fluorescent Chemosensor for Hg2+ with High Sensitivity and Selectivity Based on the Rhodamine Fluorophore

“…Herein, we synthesize compound c, (Scheme 1) in which Rhodamine B is connected to 2-hydroxy-1-naphthaldehyde through a hydrazine bridge; c is obtained through a one-step Schiff base reaction. [7] As a result of the excellent photophysical properties, such as high fluorescence, large absorption co-4438 rately. Furthermore, this "turn-on"-type fluorescent sensor, upon the addition of Hg 2+ over other competitive species, was successfully applied to bioimaging in yeast and HeLa cells.…”