2′-Deoxy-2′(S)-ethinyl oligonucleotides: A modification which selectively stabilizes oligoadenylate pairing to DNA complements

Oligonucleotides consisting of 2′-deoxy-2′(S)-ethinyl-thymidine, -uridine, and -adenosine have been prepared. Whereas the modified pyrimidine oligonucleotides uniformly lead to weaker pairing affinity with DNA and RNA complements, the corresponding adenine oligonucleotides show enhanced thermal stability in duplexes with complementary DNA and decreased stability with RNA.