Abstract
The bifunctional phosphorylating reagent O,O-bis[1-benzotriazolyl]phosphoromorpholidate was used to introduce a 5'-O-triphosphate and a 3'-O-diphosphate function in a partially protected riboguanosine. Pilot studies indicated that protection of the 2'-OH of ribonucleosides with the acid-labile tetrahydropyranyl group, instead of the more labile 4-methoxytetrahydropyran-4-yl group, was most satisfactory for the preparation of the Magic Spot II.