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The synthesis of vinylphosphonate-linked nucleotide dimers has been achieve
d using an olefin cross-metathesis (CM) reaction as a key step. The 1,3-dim
esityl-4,5-dihydroimidazol-2-ylidine-containing catalyst 5 (Grubbs' second-
generation catalyst) was found to be the superior catalyst for this transfo
rmation. Both metathesis partners were readily available using known method
ology, and the vinylphosphonate-linked dimer was produced with high levels
of (E)-selectivity (> 20:1) in 58% yield (70% based on recovered starting m
aterial).