Highly beta-selective, N-iodosuccinimide-mediated nucleosidation to bicyclo- and tricyclo-nucleosides.

The N-iodosuccinimide (NIS) induced nucleosidation of protected natural bases with bicyclo[3.3.0] sugar precursors was investigated. It was found that this method is particularly suited for the synthesis of N(1)-pyrimidine nucleosides and provides a selective entry into N(7)-purine nucleosides. This nucleosidation is beta-specific and is a valuable alternative to the Vorbrüggen method.