Oligonucleotides containing a nucleotide analog with an ethynylfluorobenzene as nucleobase surrogate

The 5′-protected 3′-phosphoramidite of 1-(2′-deoxy-β-d-ribofuranosyl)-2-ethynyl-4-fluorobenzene was prepared and employed in the synthesis of oligonucleotides. The duplex of CTTTTCF#TTCTT with AAGAAAGAAAAG, where F# is the ethynylfluorobenzene-containing nucleotide, melts higher than the duplex containing a difluorotoluene moiety.