Transition-metal-catalyzed chlorosulfonylation of 5-ethynylpyrimidine
nucleosides provided (E)-5-(β-chlorovinyl)sulfones A, which undergo nucleophilic substitution with amines or
thiols affording B. The treatment of vinyl sulfones A with ammonia followed by acid-catalyzed hydrolysis of the
intermediary β-sulfonylvinylamines gave 5-(β-keto)sulfones C. The latter reacts with electrophiles, yielding α-carbon-alkylated
or -sulfanylated analogues D. The 5′-triphosphates
of A and C were incorporated into double-stranded
DNA, using open and one-nucleotide gap substrates, by human or Escherichia coli DNA-polymerase-catalyzed reactions.