The facilated design and synthesis of chalcogen containing xanthenones and xanthylium dyes
Del Valle, David John
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The heavy-atom analogues of tetramethylrosamine have shown to be effective photosensitizers for Photodynamic Therapy (PDT), Photodynamic Antimicrobial Therapy (PACT), and for the inhibition of P-gp in vitro. In order to investigate these applications further, improvements to the synthetic route must be made, as the available routes were ineffective at delivering the products on a gram or larger scale. Each of these applications shares a common starting material, the 2,7 bis(dimethylamino)chalcogenoxanthen-9-one. Improving the yields for these photosensitizers in the separate applications meant facilitating the synthesis of chalcogenoxanthenones. Improvements made to the previous synthetic route are discussed, and a new method of ring closure to form chalcogenoxanthenones is also discussed. These methods facilitate a practical synthesis of the sulfur, selenium, and tellurium xanthenones. Subsequently, the first tellurium-containing analogue of tetramethylrosamine has now been synthesized. These improvements to the synthesis have also allowed a gram-scale production of chalcogenoxanthylium dyes.