How is 5-Nitrofluorescein (CAS: 3326-35-0) typically synthesized?

5-Nitrofluorescein (CAS: 3326-35-0) is synthesized by the nitration of fluorescein. A mixture of fluorescein and a nitration reagent (such as nitric acid) is heated under controlled conditions. The product is then purified by recrystallization from a suitable solvent. Common catalysts include sulfuric acid, and the yield is typically around 70-80%. This process requires careful control of reaction conditions to ensure selectivity and high purity.