New fluorinated nucleoside analogues with 2-butenolide rings prepared by nucleophilic vinylic fluorine displacement in 4,4-dialkyl-2,3-difluorobut-2-en-4-olides
New fluorinated nucleoside analogues with 2-butenolide rings prepared by nucleophilic vinylic fluorine displacement in 4,4-dialkyl-2,3-difluorobut-2-en-4-olides