PROCESS FOR THE SYNTHESIS OF 4,5,6,7-TETRACHLORO-3,6-DIHYDROXY- 2,4,5,7-TETRAIODO-3H-SPIRO[ISOBENZOFURAN-1,9-XANTHEN]-3-ONE (ROSE BENGAL) AND RELATED XANTHENES 4567--36--2457--3H-[-1 9-]-3-()

A new process for the manufacture of iodinated xanthenes in high purity includes a cyclization step followed by an iodination step. No extraction, chromatographic or solvent concentration steps are required, and the intermediate as well as final compounds are isolated via filtration or similar means. The process requires a single organic solvent, and the steps are completed at temperatures below 100° C. The exclusion of chloride ions, of chloride free-radicals, hypochlorite ions, or hypochlorous acid as reagents or from reagents that may generate these species in situ in the presence of oxidants, prevents undesirable impurity formation. Several new compounds have been conceived and isolated using these methods. These new compounds are also formed into new medicaments.