Functionalization of 2'-amino-LNA with additional nucleobases.

Thymin-1-yl-acetic acid and adenin-9-yl-acetic acid have been coupled to the N2'-atom of a 2'-amino-LNA thymine nucleoside, and these "double-headed" LNA monomers have been incorporated into oligodeoxyribonucleotides via their corresponding phosphoramidite derivatives. Oligonucleotides containing these modified nucleotides show in most cases increased thermal stability when forming duplexes with complementary DNA, even allowing multiple incorporations. Incorporation of "double-headed" LNA monomers in both strands also led to stable duplexes, however, no indication of Watson-Crick base pairing between the extra nucleobases could be found.