J. Ravn et al., A conformationally locked tricyclic nucleoside. Synthesis, crystal structure and incorporation into oligonucleotides, J CHEM S P1, (16), 2001, pp. 1855-1861
A tricyclic nucleoside is synthesised from a bicyclic nucleoside precursor
by applying a stereoselective dihydroxylation, a regioselective tosylation
and an intramolecular ether formation. This tricyclic nucleoside is constru
cted as a conformationally locked thymidine analogue and has been analysed
by X-ray crystallography. Thus, the furanose ring of this nucleoside adopts
a perfect S-type conformation and the torsion angle gamma, describing the
C4'-C5' bond is restricted in the +ac range. The tricyclic nucleoside is in
corporated into two nonameric oligonucleotide sequences displaying strongly
decreased affinity towards complementary DNA and RNA when compared to the
corresponding unmodified oligodeoxynucleotide sequences.