AN ACYCLIC 5-NITROINDAZOLE NUCLEOSIDE ANALOG AS AMBIGUOUS NUCLEOSIDE

Acyclic nucleoside analogues with carboxamido- or nitro-substituted he terocyclic bases have been evaluated for their possible use as univers al bases in oligodeoxynucleotides. The acyclic moiety endows the const ructs with enough flexibility to allow good base stacking. The 5-nitro indazole analogue afforded the most stable duplexes among the acyclic derivatives with the least spread in T-m versus the four natural bases . In spite of the acyclic moiety, stabilities are comparable with thos e of duplexes incorporating the recently described 5-nitroindole nucle oside analogue, but considerably exceed those for the 3-nitropyrrole a nalogue.