... 2. 3',6'-Di-O-acetyl-4-nitrofluorescein (à 3',6'-Bis(acetyloxy)-4-nitrospiro[isobenzofuran-1(3H), 9'- [9H]xanthen]-3-one; 5). The mother liquor of 6 was concentrated to a smaller volume to give a second fraction of 6 (2 g). The filtrate was ... Helvetica Chimica Acta ± Vol. 86 (2003) 2315 ...