New synthetic routes to synthons suitable for 2'-O-allyloligoribonucleotide assembly.

New synthetic routes have been devised for the high yield preparation of protected 2'-O-allylribonucleoside-3'-O-phosphoramidites, exemplified by the ribonucleosides guanosine and 2,6-diaminopurine riboside (2-aminoadenosine). Key features are the use of versatile intermediates and an easy allylation step. The development of a novel synthon based on 2'-O-allyl-2,6-diaminopurine riboside enables short 2'-O-allyl-oligoribonucleotide probes to be synthesized with adenine replaced by 2-aminoadenine. Thus very stable hybrids with complementary RNA target sequences can be formed due to the formation of the three hydrogen bond 2-amino A.U base pairs.