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

Sodium salts of adenine, 2,6-diaminopurine, cytosine, 4-methoxypyrimidin-2-one and aliphatic or alicyclic amines reacted with 4,4-dialkyl-2,3-difluorobut-2-en-4-olides by vinylic substitution of fluorine to give 3-substituted butenolides as nucleoside analogues or enamines, while sodium and lithium salts of aliphatic and aromatic amines reacted as hard nucleophiles to attack the carbonyl group thus causing butenolide ring opening.