Synthetic utility of an isolable nucleoside phosphonium salt

The reaction of O-6-benzyl-3',5'-bis-O-(tert-butyldimethylsilyl)-2'-deoxyxanthosine with 1H-benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP) yielded the nucleoside C-2 tris(dimethylamino)phosphonium hexafluorophosphate salt as a stable, isolable species. This is in contrast to reactions of inosine nucleosides with BOP, where the in situ formed phosphonium salts undergo subsequent reaction to yield O-6-(benzotriazol-1-yl)inosine derivatives. The phosphonium salt obtained from the 2'-deoxyxanthosine derivative can be effectively used to synthesize M-modified 2'-deoxyguanosine analogues. Using this salt, a new synthesis of an acrolein-2'-deoxyguanosine adduct has also been accomplished.