Base−Base Interactions in the Minor Groove of Double-Stranded DNA

A method has been developed for the synthesis of bisheaded nucleosides with thymine and adenine base moieties. We have demonstrated that, when incorporated in oligonucleotides, extrahelical A−T base interactions are possible when the bisheaded nucleosides are positioned in opposite strands of the duplex and are separated from each other by one regular base pair.