Formation of a Methide Derivative upon Photolysis of Thymidine Bromohydrins

Reaction of bromine with thymidine in aqueous solution produces, in high yield, the corresponding 5-bromo-6-hydroxy-5,6-dihydroderivative (thymidine bromohydrins). UVC photolysis of thymidine bromohydrins gives rise to a reactive intermediate that is converted into 5-(hydroxymethyl)-2'-deoxyuridine upon incubation in water. When the former compound is left in methanol, ethanol, or propanol, the corresponding 5-alkoxymethyl derivatives are produced. The proposed structure for the primary photolysis product of thymidine bromohydrins is a methide derivative of the thymine ring. This compound could be an interesting intermediate in the synthesis of methyl-substituted thymidine.