How is 3,6-Diamino-9-[2-(methoxycarbonyl)phenyl]xanthenium chloride (CAS: 62669-70-9) typically synthesized?

3,6-Diamino-9-[2-(methoxycarbonyl)phenyl]xanthenium chloride (CAS: 62669-70-9) is typically synthesized via the coupling of 3,6-diaminobenzanthrone with 2-(methoxycarbonyl)benzaldehyde. The reaction involves protecting the amine groups, coupling them with the aldehyde, and then chlorinating the resulting product to form the xanthenium chloride. Common catalysts include palladium(II) acetate and triphenylphosphine. The yield is generally around 70%, and the reaction is performed under mild conditions to ensure selectivity.