5-Nitrofluorescein (3′,6′-dihydroxy-6-nitrospiro[2-benzofuran-3,9′-xanthene]-1-one) is a key intermediate in the synthesis of various fluorescent compounds such as 5-aminofluorescein (5-amino-3′,6′-dihydroxy-3H-spiro[isobenzofuran-1,9′-xanthen]-3-one), fluorescein 5-isothiocyanate (FITC; 3′,6′-dihydroxy-5-isothiocyanato-3H-spiro[isobenzofuran-1,9′-xanthen]-3-one), and fluorescein lisicol (previously known as cholyl-lysylfluorescein or CLF.
Process for the preparation of 5-/6-nitrofluorescein(
US20120220787A1)