Synthesis and evaluation of the functional oligonucleotides-PEG conjugates.

We have previously demonstrated that the phenylsulfide and phenylsulfoxide derivatives of 2-amino-6-vinylpurine exhibit efficient cross-linking with high selectivity towards cytidine through synchronous activation within duplex. In this study, we synthesized their conjugates with PEG for possible application to in vitro as well as in vivo antisense agents. Thus, the ODN (2) with the antisense sequence toward luciferase was synthesized, having the 2-amino-6-vinylpurine nucleoside analog at the reactive site for targeting C and the amino linker at the 3' terminal. The vinyl group was transformed to the corresponding substituted phenylsulfide derivatives (3), and then the amino group of the 3' end was converted to the thiopropionyl group (4). The thiol nucleophile of 4 was reacted to the acid-responsive PEG2 in good isolated yields (55-62%).